WO2003106445A1

WO2003106445A1 - Compounds and methods for controlling bacterial virulence

Info

Publication number: WO2003106445A1
Application number: PCT/DK2003/000388
Authority: WO
Inventors: John Nielsen; Michael Givskov
Original assignee: QSI PHARMA AS
Current assignee: QSI PHARMA AS
Priority date: 2002-06-12
Filing date: 2003-06-12
Publication date: 2003-12-24
Anticipated expiration: 2004-12-12
Also published as: AU2003232173A1

Abstract

Novel sulfonated homoserine lactones formula I have been found to act ac quorum sensing inhibitors. As such, they may be useful in the treatment of bacterial infections.

Description

COMPOUNDS AND METHODS FOR CONTROLLING BACTERIAL VIRULENCE

FIELD OF THE INVENTION

The invention relates to a novel class of sulfonamides exerting a quorum sensing inhibiting effect on bacteria, such as Pseudomonas aeruginosa. The invention also provides pharmaceutical compositions comprising said compounds and methods of treatment of infections comprising the administration of said compounds to a patient in need thereof.

BACKGROUND OF THE INVENTION

Pseudomonas aeruginosa is a Gram-negative aerobic rod bacterium widely distributed in nature. Pseudomonas aeruginosa is an opportunistic pathogen, and infections by Pseudomonas aeruginosa may have serious consequences and even a fatal outcome for the patients. It has been reported that Pseudomonas aeruginosa may cause the death of patients with burns [Richard, J. Infec. D/s., 170, 377, 1994] and nosocomial pneumonia in intubated [Bowton, Chest, 115, 28S, 1999] and neutropenia cancer patients [Bergen, Infect. Dis. Clin. N. Am., 10, 297, 1996], It is also well-known that people suffering from cystic fibrosis are often chronically infected by Pseudomonas aeruginosa, and that such an infection may cause lethal respiratory failure. According to Govan, [Microbiol Rev. ,60, 539, 1996] more than 80% of cystic fibrosis patients have Pseudomonas aeruginosa in their lungs when they reach their mid-twenties.

The pathogenicity of Pseudomonas aeruginosa is caused by a number of extracellular compounds produced by the bacterium, examples of which are proteases (elastase, stapholytic protease and alkaline protease), pigments (pyocyanin and pyoverdin) and haemolysins. These extracellular compounds are often referred to as virulence factors. It is now well established that the excretion of virulence factors is controlled by a quorum sensing system. The quorum sensing system is an arrangement of signal molecules, receptors, signal molecule synthases and the corresponding genes which enable bacteria to monitor their own population density, and to express certain genes as a function of the density. In particular, a quorum sensing system in Pseudomonas aeruginosa allows the bacterium to produce and excrete virulence factors dependent on the population density [Hentzer et al., Laboratory Medicine, 33, 295, 2002] . Pseudomonas aeruginosa infections often take the form of biofilms. Biofilms may be defined as an association of microorganisms that grow attached to a surface and produce a slime layer predominantly composed of polysaccharides to form a protective layer. Biofilms are far less susceptible to antibiotics than the corresponding planktonically growing bacteria. In particular, Pseudomonas aeruginosa in cystic fibrosis patients appear to grow as biofilms in the lungs, and the bacterium is also found to grow as biofilm on infected implants [Steckler, Appl. Environ. Microbiol., 64, 3486, 1998]. Such infections are therefore often extremely difficult to treat. The standard therapy for Pseudomonas aeruginosa infected cystic fibrosis patients involves isolation of the patient and administration of large amounts of a cocktail of antibiotics. Unfortunately, this treatment is expensive, the isolation may have obvious adverse repercussions for the patient, and many patients become allergic to the antibiotics administered [Høiby, Thorax, 45, 881, 1990]. Moreover, the infection is not eradicated but only controlled by this treatment, and the prolonged and extensive use of antibiotics constitutes a serious risk for development of resistance.

The formation of biofilm per se is not controlled by the quorum sensing system. However, it has been shown that biofilms established in the presence of a quorum sensing inhibitor or biofilms established by bacteria devoid of a functional quorum sensing system appear immature and less persistent. [Hentzer et al., Microbiology 148, 87, 2002, Davies et al., Science, 280, 295, 1998].

Interestingly, inhibition of quorum sensing systems appears to be used as a natural defence mechanism by various primitive organisms that are devoid of immune systems. Some have evolved to rely, at least in part, on secondary metabolite chemistry for protection against colonizing organisms. Givskov et al., J. Bacteriology, 178, 6618, 1996 and Manefield et al., Microbiology, 145, 283, 1999 describes that the marine red algae Delisea pulchra produces a number of halogenated furanones which act as quorum sensing inhibitors and by which the algae controls bacterial colonisation of its surface.

Bacteria causing chronic infections, in particular biofilm forming bacteria, such as Pseudomonas aeruginosa are difficult to treat, and it is an object of the present invention to provide novel compounds and methods effective in the treatment of such infections.

The idea of employing quorum sensing inhibitors for therapy is known in the art. For example, WO 99/27786 teaches the use of compounds of the formula

wherein n is 2 or 3; Y is 0, S or NH; X is O, S or NH; and R is Cι-ι₈ alkyl or acyl to control biofilm formation by pathogenic bacteria by inhibiting the quorum sensing system.

WO 98/58075 discloses a method of regulating biofilm development comprising the administration of Λ/-(3-oxododecanyl)-L-homoserine lactone, butyryl-L-homoserine lactone or their analogues. The effect of the compounds is said to be exerted by inhibiting the process of signal reception of the quorum sensing system.

WO 97/27851 discloses a method of inhibiting growth of a mycobacterium comprising administering L-homoserine, L-homoserine lactone or precursors thereof to a patient.

US 6,057,288 discloses a therapeutic composition which inhibits the activity of the LasR protein (part of the quorum sensing system) in Pseudomonas aeruginosa.

WO 96/29392 discloses a method of inhibiting e.g. homoserine lactone signal reception of the quorum sensing system in microorganisms by exposing said organisms to halogenated derivatives of furanone compounds.

WO 03/039549 discloses quorum sensing inhibitors which are amide, cabazide, hydrazide, urea or guanidine derivatives, for use in treating infections caused by Gram- negative bacteria.

WO 03/039529 discloses quorum sensing inhibitors which are amide or 1,2- acylhydrazine derivatives for use in treating infections caused by Gram-negative bacteria.

SUMMARY OF THE INVENTION

The invention provides compounds of general formula I

wherein RI is alkyl, alkenyl, alkynyl or heteroaryl, each of which being optionally substituted with one or more alkyl, hydroxy, halogen, haloalkyl, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonylalkyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino, alkylcarbonylamino, aryl or heteroaryl, each aryl or heteroaryl optionally being substituted with one more alkyl, hydroxy, halogen, amino, cyano, carboxy, haloalkyl, alkylcarbonyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino or alkylcarbonylamino; or a radical of the formula -(R^a-Z-R^b-)_n-H, wherein each R^a independently represents a Ci-₁₈ straight or branched, saturated or unsaturated hydrocarbon diradical optionally substituted by hydroxy, halogen, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonylalkyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino, alkylcarbonylamino, aryl or heteroaryl, and wherein each R^b independently represents a bond or a Cι-₁₀ straight, branched and/or cyclic hydrocarbon diradical, optionally substituted by hydroxy, halogen, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino, alkylcarbonylamino or phenyl; n being 1, 2 or 3; Z represents O, C(O), C(0)-0, NH or an aromatic or non-aromatic heterocyclic diradical;

R2 is hydrogen, alkyl, alkenyl or alkynyl, each of which being optionally substituted with one or more hydroxy, halogen, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonylalkyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, alkoxycarbonylalkyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino, alkylcarbonylamino, aryl or heteroaryl, wherein said aryl or heteroaryl may optionally be substituted by on one more hydroxy, halogen, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, alkoxycarbonylalkyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino or alkylcarbonylamino; or a radical of the formula -(R^a-Z-R^b)_n-H; X represents 0 or S; Y represents 0, S or NR9, wherin R9 represents hydrogen, alkyl or phenyl; each R3, R4, R5, R6, R7 and R8 are independently hydrogen, alkyl, alkenyl, alkynyl, hydroxy, halogen, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonylalkyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, alkoxycarbonylalkyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino, alkylcarbonylamino or phenyl; or wherein R4 and R5 and/or R6 and R7 together with the two ring carbon atoms to which they are attached form a 5 or 6 membered carbocyclic or heterocyclic ring; one of R3, R4, R5, R6, R7 and R8 being absent to provide a vacant valence for binding to the nitrogen; with the proviso that if RI is methyl then Y is not S; and pharmaceutically acceptable salts or degradation products thereof.

In another aspect, the invention provides the use of compounds of formula I in therapy, and in particular the invention provides pharmaceutical compositions comprising compounds of formula I.

In a further aspect, the invention provides methods of treating or preventing infections in humans or animals, the method comprising administering to a patient in need thereof an effective amount of a compound according to formula I.

In a still further aspect, the invention provides the use of a compound according to formula I in the manufacture of a medicament for the treatment or prevention of infections.

DETAILED DESCRIPTION OF THE INVENTION

In the present context, the term "alkyl" is intended to indicate a univalent radical derived from straight, branched and/or cyclic alkane by removing a hydrogen atom from any carbon atom. Said alkyl preferably comprises 1-18, e.g. 4-12 carbon atoms. The term includes the subclasses primary, secondary and tertiary alkyl, such as methyl, ethyl, n- propyl, isopropyl, n-butyl, sec. -butyl, isobutyl, tert. -butyl, isopentyl, isohexyl, cyclohexyl, cyclopentyl and cyclopropyl. The term "alkenyl" is intended to indicate a univalent radical derived from a straight, branched and/or cyclic alkene be removing a hydrogen atom from any carbon atom. Said alkenyl preferably comprises 2-18, e.g. 4-12 carbon atoms. The term includes the subclasses of primary, secondary and tertiary alkenyl. Alkenyl may include more than one carbon-carbon double bond, and any carbon-carbon double bonds may be of either E or Z stereochemistry where applicable. The term includes, vinyl, allyl, 1-butenyl, 2- butenyl, and 2-methyl-2-propenyl and 2,4-pentenedienyl.

The term "alkynyl" is intended to indicate univalent radical derived from a straight or branched alkyne by removal of a hydrogen atom from any carbon atom. Said alkynyl preferably comprises 2-12, e.g. 2-6 carbonatoms. The term includes the subclasses of primary and secondary alkynyl. Alkynyl may include one or more carbon-carbon triple bonds, and it may also include one or more carbon-carbon double bonds. The term includes ethynyl and propynyl.

The term "halogen" is intended to indicate members of the seventh main group from the periodical table, i.e. fluoro, chloro, bromo and iodo.

The term "haloalkyl" is intended to indicate an alkyl group as defined above substituted with one or more halogen atoms as defined above.

The term "amino" is intended to indicate a radical of the formula -NR"₂, wherein each R" independently represents hydrogen or alkyl as indicated above. The term may also include quaternary amino groups, i.e. radicals of the formula -NR'₃ ⁺, wherein each R' independently represents alkyl as indicated above.

The term "alkylcarbonyl" is intended to indicate a radical of the formula -C(0)-R', wherein R' represents an alkyl as indicated above.

The term "alkylcarbonylalkyl" is intended to indicate a radical of the formula R'-C(0)-R", wherein R' and R" are alkyl as defined above.

The term "alkylcarbonyloxy" is intended to indicate a radical of the formula -0-C(0)-R', wherein R' represents an alkyl as indicated above. The term "alkoxy" is intended to indicate a radical of the formula -O-R', wherein R' represents an alkyl as indicated above.

The term "alkoxycarbonyl" is intended to indicate a radical of the formula -C(0)-0-R', wherein R' represents alkyl as indicated above.

The term "alkoxycarbonylalkyl" is intended to indicate a radical of the formula -R-C(O)- O-R', wherein R and R' represent alkyl as indicated above.

The term "aminocarbonyl" is intended to indicate a radical of the formula -C(0)-NR"₂ or -C(0)-NR'₃ ⁺, wherein each R' independently represents alkyl as indicated above, and each R" independently represents hydrogen or alkyl as indicated above.

The term "aminocarbonylalkyl" is intended to indicate a radical of the formula -R'-C(O)- NR"₂ or -R'-C(0)-NR'₃ ⁺, wherein each R' independently represents alkyl as indicated above, and each R" independently represents hydrogen or alkyl as indicated above.

The term "thio" is intended to indicate a radical of the formula -S-R", wherein R" represent hydrogen or alkyl as indicated above.

The term "alkylthio" is intended to indicate a radical of the formula -R'-S-R", wherein R' independently represents alkyl as indicated above, and R" independently represents hydrogen or alkyl as indicated above.

The term "aminosulfonyl" is intended to indicate a radical of the formula -S(0)₂-NR"₂ or -S(0)₂-NR'₃ ⁺, wherein each R' independently represents alkyl as indicated above, and each R" independently represents hydrogen or alkyl as indicated above.

The term "alkylsulfonylamino" is intended to indicate a radical of the formula -NR"- S(0)₂-R" or -NR'₂ ⁺-S(0)₂-R", wherein each R' independently represents alkyl as indicated above, and each R" independently represents hydrogen or alkyl as indicated above.

The term "alkylcarbonylamino" is intended to indicate a radical of the formula -NR"- C(0)-R" or -NR'₂ ⁺-C(0)-R", wherein each R' independently represents alkyl as indicated above, and each R" independently represents hydrogen or alkyl as indicated above. The term "aryl" is intended to indicate radicals of carbocyclic aromatic rings, optionally fused bi-, tri- or tetra-cyclic rings wherein at least one ring is aromatic, e.g. phenyl, naphthyl, indanyl, indenyl, 1,4-dihydronaphtyl, flourenyl or tetralinyl.

The term "heteroaryl" is intended to indicate radicals of heterocyclic aromatic rings, in particular 5- or 6-membered rings with 1-3 heteroatoms selected from 0, S and N, or optionally fused bicyclic rings, at least one of which is aromatic, comprising 1-4 heteroatoms, e.g. pyrrolyl, furanyl, thiophenyl, imidazolyl, oxazolyl, thiazolyl, pyrazolyl, pyridyl, pyrimidyl, purinyl, quinolinyl, chromenyl or carbazolyl.

The term "hydrocarbon" is intended to indicate a compound containing only hydrogen and carbon atoms, it may contain one or more double and/or triple carbon-carbon bonds, and it may comprise cyclic moieties in combination with branched or linear moieties. Said hydrocarbon preferably comprises 1-20, e.g. 1-18, e.g. 1-12 carbon atoms. The term includes alkyl, alkenyl, alkynyl and aryl, as indicated above.

The term "aromatic or nonaromatic heterocyclic diradical" is intended to indicate a diradical of 5- or 6-membered cyclic compounds, either aromatic or nonaromatic, with one or more hetero atoms selected from amongst N, O and S, e.g. thiophene, furan, tetrahydrofuran, pyrrole, pyridine and morpholine.

The term "pharmaceutically acceptable salt" is intended to indicate salts prepared by reacting compounds of formula I comprising acid or basic groups with suitable bases or acids, respectively. Examples of such acids are hydrochloric, hydrobromic, hydroiodic, sulfuric, nitric, acetic, phosphoric, lactic, maleic, phthalic, citric, propionic, benzoic, glutaric, gluconic, methanesulfonic, salicylic, succinic, tartaric, toluenesulfonic, sulfamic and fumaric acid. Examples of such bases are potassium hydroxide, sodium hydroxide, ammonia and amines.

The term "degradation products" is intended to indicate compounds whose structure is altered compared to the compounds of formula I and which are formed as a result of , addition of nucleophiles, ring-openings, rearrangements or nucleophilic or electrophilic substitution reaction including hydrolysis reactions during storage of the compound or before, during, or after administration of the compound. Such degradation products could be formed by ester hydrolysis such as lactone ring-opening, by hydrolysis of haloalkyl substituents, by Michael-type additions to conjugated double-bonds, by aromatic substitution reactions on activated aromatic or heteroaromatic scaffolds, by ring-opening of heteroaromatic scaffolds such as the furan or thiophene heterocycle following a retro-Pahl-Knorr mechanism, or by aldol-condensation of such dicarbonyl compounds formed from the above-mentioned Pahl-Knorr mechanism, or other reactions with nucleophiles commonly found in aqueous buffers or solutions or following pathways familiar to those skilled in the art and commonly used such as the reactions which appear in Advanced Organic Synthesis by Jerry March (5. Ed.) or a similar standard organic chemistry textbook.

The terms "effective amount" or "effective dose" are used interchangeably and are both intended to indicate an amount of the compound which allows it to perform its intended therapeutic function in the body of a human or animal. This amount will vary according to the patient, the disease, and the desired effect. It lies within the capabilities of skilled physicians and veterinarians to determine such an amount.

Preferred compounds of formula I

In a preferred embodiment, the invention relates to a compound according to formula I with the structure of formula la, lb or lc

In another preferred embodiment, RI is alkyl, optionally substituted by one or more phenyl. Especially preferred in this embodiment, RI is C-.-₁0 alkyl optionally substituted as indicated above. In particular, RI can be selected from the group consisting of 2- oxopropyl, 3-benzoyloxypropyl, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, 3- phenylpropyl, 4-phenylbutyl, 5-phenylpentyl, 6,6-diphenylhexyl and 6,6-dimethylheptyl, 5-chloromethyl-2-furyl and 5-dichloromethyl-2-furyl.

In another preferred embodiment, Z is 0 or C(O). In another preferred embodiment, R3 is hydrogen. In a further preferred embodiment, X and Y are both 0. In a still further preferred embodiment, Y is NH, and in a still further preferred embodiment, X is S.

In still another preferred embodiment, R5 and R7 are both hydrogen, while R6 and R8 are independently selected from amongst the group consisting of alkyl, aminocarbonyl and R^a-0-R^b-H, wherein R^a and R^b are as defined above.

Particular example of compounds according to formula I include

N-methanesulfonyl-L-homoserine lactone;

N-ethanesulfonyl-L-homoserine lactone;

N-propanesulfonyl-L-homoserine lactone; N-butanesulfonyl-L-homoserine lactone;

N-pentanesulfonyl-L-homoserine lactone;

N-hexanesulfonyl-L-homoserine lactone;

N-heptanesulfonyl-L-homoserine lactone;

N-(2-oxo-propanesulfonyl)-L-homoserine lactones; N-(3-phenylpropane-l-sulfonyl)-L-homoserine lactone;

N-(4-phenylbutane-l-sulfonyl)-L-homoserine lactone;

N-(5-phenylpentane-l-sulfonyl)-L-homoserine lactone;

N-(3-benzyloxypropane-l-sulfonyl)-L-homoserine lactone;

Λ/-(6,6-diphenylhexane-l-sulfonyl)-L-homoserine lactone; N-(6,6-dimethylheptane-l-sulfonyl)-L-homoserine lactone;

N-(5-chloromethyl-2-furansulfonyl)-L-homoserine lactone; or

N-(5-dichloromethyl-2-furansulfonyl)-L-homoserine lactone.

Compounds according for formula I comprise asymmetric carbon atoms and may comprise carbon-carbon double bonds, and this allows for the existence of stereo and geometric isomers. It is to be understood that the present invention relates to all such isomers, either in pure form or as mixtures thereof. Quorum sensing

Some bacteria have a system by which they can monitor the density of their own population and control the expression of specific genes only when a certain population density has been reached. This ability to monitor cell density has been found in more than 20 different bacterial species, and has been termed quorum sensing.

The existence of quorum sensing was established in the early 1970s where experiments showed that bioluminescence of the bacterium Vibrio fischeri is a function of cell density, and that it is controlled by a small diffusible molecule, later identified to be a Λ/-acyl- homoserine lactone (AHL), namely Λ/-(3-oxohexanoyl)-L-homoserine lactone.

The quorum sensing system of V. fischeri serves well as a basis for describing and understanding quorum sensing systems. It comprises a signal molecule synthase (Luxl) which produces the signal molecule (AHL, in casu Λ/-(oxo-hexanoyl)-L-homoserine lactone) from a precursor, and a signal molecule dependent receptor protein (LuxR). When the concentration of the signal molecule reaches a threshold level, i.e. when the population of the bacterium reaches a certain level, the signal molecule interacts with the receptor protein to effect an activation of it. The LuxR-AHL complex binds to the lux box in the promoter region of the gene, which, in turn, initiates the transcription of luxl (the gene encoding Luxl) and other genes responsible for bioluminescense. The Luxl production thus generates a positive autoregulatory loop. The signal molecules are often referred to as autoinducers.

Many Gram-negative bacteria have been shown to posses one or more quorum sensing systems homologues to the LuxR/LuxI system just described for V. fischeri, and Pseudomonas aeruginosa in particular appears to have at least two quorum sensing systems, i.e. las and rhl. The las system comprises a signal molecule generating synthase (Lasl), the major product of which is Λ/-(3-oxo-dodecanoyl)-homoserine lactone (OdDHL), and a receptor protein LasR. The rhl system comprises a signal generating synthase (Rhll), the major product of which is Λ/-butyryl-homoserine lactone, and a receptor protein RhlR. The las system modulates the expression of Lasl, Rhll, and virulence factors, such as elastase, staphylolytic protease, alkaline protease, exotoxin and neuraminidase, and biofilm differentiation. The rhl system modulates the expression of Rhll, rhamnolipid and virulence factors, such as alkaline protease, elastase, haemolysin, pyocyanin and hydrogen cyanide. Moreover, in vitro immunoassays on human leukocytes have shown that OdDHL possesses immunomodulatory properties, e.g. inhibition of lymphocyte proliferation and down-regulation of tumor necrosis factor alpha production and of IL-12 production (Telford et al., Infect. Immun, 66, 36, 1998). In addition, OdDHL has been demonstrated to activate T-cells in vivo to produce the inflammatory cytokine interferon-γ (Smith et al., J. Immunol., 167, 366, 2001) and, thereby, potentially promote a Th2-dominated response leading to increased tissue damage and inflammation.

An important effect of a quorum sensing system is that, e.g. virulence factors are only excreted when the population has reached a certain density. This is probably of vital importance for invading organisms because they, at low density, are more susceptible to the defence systems of the host. If an invading organism unveiled its presence by excreting virulence factors when still at a low population density, they would be more easily targeted by the hosts defence mechanisms A quorum sensing system endows bacteria with a capability to reach a critical population density whereby they overwhelm the host's immune defence and establish an infection.

The rationale behind quorum sensing based drugs is multifaceted. By preventing the excretion of virulence factors, the pathogenecity of the invading organism is diminished, or even eliminated. Furthermore, as described above, the signal molecules may themselves have an adverse effect on the immune system of the host, so inhibiting the production of signal molecules will have a beneficial effect. Finally, the development of persistent biofilms in some bacteria, e.g. Pseudomonas aeruginosa is also affected by the quorum sensing system (Hentzer et al., Microbiology 148, 87, 2002). Although the biofilm itself may not be virulent, it protects the invading organism from the defence systems of the host. By preventing the formation of persistent biofilms, the invading organism is left exposed to the defence systems of the host, and the host may thus be able to clear the infection on its own. Alternatively, the infectious organism will be left more receptive to treatment with conventional antibiotics. It is thus envisaged that an embodiment of the invention involving a combination treatment, wherein a quorum sensing inhibitor of the present invention and an antibiotic is administered to a patient will be particular beneficial for certain types of infections.

It is important to note that as described above, inhibiting the quorum sensing system as such will not have a toxic effect on the bacterium, and it is believed that this will have a major impact on the build-up of resistance towards such drugs. On current understanding, resistance to antibiotics is generated under the imposition of a selection pressure favouring mutants that are capable of tolerating the toxins. Quorum sensing inhibitors as such are non-toxic, and they are therefore not expected to impose a selection pressure on the bacteria. As a consequence, the formation of resistant strains is expected to be at a minimum, i.e. the background mutational rate. A preferred embodiment of the invention thus provides non-toxic compounds of formula I. Toxicity may be quantified in a simple assay wherein the bacterium Escherichia coli is left to grow planktonic in the absence or presence of a test compound. Bacterial cultures are grown in ABt minimal medium supplemented with 0.5% casamino acids and 0.5 % glucose (referred to as growth medium). The ABt medium contains: (NH )₂S0₄ (2g/L), Na₂HP0₄*2H₂0 (6 g/L), KH₂P0₄ (3 g/L), NaCl (3 g/L), MgCI₂ (93 mg/L), CaCI₂ (11 mg/l), and thiamine (0.5 mg/L). Culture conditions: The 20 ml cultures were grown in 100 ml conical flasks in an orbital air shaker at 200 rpm at 37°C. The cultures are inoculated from overnight cultures in fresh medium at an optical density of approximately OD450=0.2. The cultures are grown to OD450=1.0, then diluted in fresh test medium to OD450=0.2. Growth is monitored by OD450 every 5 min. Compounds, which at concentration lower than 10 mM, e.g. lower than 1 mM, e.g. lower than 500 μM, e.g. lower than 100 μM cause an increase of the doubling time during the exponential growth phase relative to the doubling time in the absence of the compound by more than 5%, e.g. 10%, e.g. more than 30%, such as more than 60%, such as more than 95% are said to be toxic.

The absence of toxicity is also believed to reduce the number of adverse effects. Treatments involving traditional antibiotics are often connected with unpleasant side effect, e.g. diarrhoea caused by the effect of the antibiotics on the beneficial bacteria present in the gut. As quorum sensing inhibitors are non-toxic, they are not expected to affect other bacteria than those exploiting a quorum sensing system and the number of adverse effects is thus likely to be reduced.

Different assays are described in the literature by which to assess if a given compound is a quorum sensing inhibitor. WO 00/06177 discloses a method that assesses the extent to which the activity of the signal molecule synthase is modulated by a given test compound. The method provides a labelled homoserine lactone substrate, allows the reaction to proceed to completion and determines the extent of the homoserine lactone substrate to homoserine lactone conversion in the absence and presence of the test compound.

Wu, et al., Microbiol 146, 2481, 2000, and Andersen et al., Appl. Envirom. Microbiol., 67, 575, 2001, describe how part of the quorum sensing system, i.e. the luxR and the luxl promoter from Vibrio fischeri may be fused with a gene encoding unstable versions (Andersen et al., Appl Environ Microbiol 64,2240,1998) of the green fluorescence protein (gfp). This fusion (referred to as the LuxR-QS-monitor) may be incorporated into bacterial strains which, if exposed to a signal molecule, will produce Gfp which can be detected by epifluorescence spectroscopy. WO 01/18248 discloses the use of other reporter genes than gfp, e.g. luciferase. The quorum sensing inhibiting effect of a given compound may also be quantified in an assay wherein the lasR and the lasB promoter from Pseudomonas aeruginosa fused with the gene encoding unstable Gfp (referred to as the LasR-QS-monitor) is incorporated into the chromosome of Pseudomonas aeruginosa or a plasmid vehicle as disclosed in Hentzer et al, Microbiol, 148, 87, 2002.

Manefield et al, Microbiology, 148, 1119, 2002, describe a method to scientifically demonstrate and quantify the QSI activity of compounds. E. coli, into which the LuxR- QS-monitor was incorporated, was inoculated from an overnight culture in fresh culture medium at a density of approximately OD450=1, and incubated at 37 °C for approximately 30 min. Aliquots (200 μl) of this culture were distributed to the wells of microtiter dishes into which a known signal molecule, namely Λ/-(3-oxo-hexanoyl)-L- homoserine lactone (OHHL) at 25, 50 and 100 nM , and the test compound had been pipetted. After two hours of incubation at 37 °C the relative fluorescence units (RFU) of each sample were captured with in Wallac Victor², 1420 Multilabel Counter using a 485 nm excitation filter and a 535 nm emission filter. The RFU values obtained for each concentration were used to calculate an inhibition index expressing the quantity of test compound per quantity of OHHL required to inhibit LuxR controlled Pluxl-gfp expression to a given level (X %). This is termed the ID_X value. The three values obtained, one for each OHHL concentration, were plotted as a function of OHHL concentration and the gradient of the best straight line fitted to the three points and passing through the origin was taken as the inhibition index (II_X). The II_X expresses the number of μmol of test compound per nanomole OHHL required to inhibit expression of fluorescence to X % of the untreated sample. A low II_X value may therefore be interpreted as to reflect a compound with high efficacy. Test compounds with II_X lower than 10, e.g. lower than 5, e.g. lower than 1, e.g. lower than 0.5, e.g. lower than 0.1, e.g. lower than 0.05 for X higher than 10%, such as higher than 20%, such as higher than 40%, such as higher than 60%, such as higher than 95% are termed quorum sensing inhibitors. Particular preferred compounds of the present invention are quorum sensing inhibitors.

The assays discussed above use parts of the quorum sensing system from particular bacteria incorporated into particular bacteria. Despite that, it has been found that such reporter systems function in a number of different bacteria, and that they are responsive to a variety of quorum sensing inhibitors [Manefield et al, Microbiology, 148, 1119, 2002]. The applied assay is therefore useful to identify compounds which inhibit the quorum sensing system in a wide range of bacteria, e.g. Pseudomonas aeruginosa.

Sulfonamides are known in therapy in general, and as antibiotics in particular. In fact, sulfonamides initiated the area of chemotherapeutic intervention against infections in the early 1930s. Sulfonamide drugs are derivatives of sulphanilamide, i.e.

Sulfonamide drug affect the folic acid synthesis, which is vital for the synthesis of purine, and thus ultimately of DNA [Kuchers in The Use of Antibiotics, p805-836, Butterworth, Oxford, 1997]. Sulfonamide drugs are thus toxic to bacteria, and the mode of action, as well as the structure, are quite different from that of quorum sensing inhibitors of the present invention.

In an embodiment, the invention relates to compounds of formula I for use in therapy, and in particular to pharmaceutical formulation comprising a compound of formula I, optionally together with other therapeutically active compounds, and optionally together with pharmaceutically acceptable carrier(s). The carrier(s) must be "acceptable" in the sense of being compatible with the other ingredients of the formulations and not deleterious to the recipient thereof.

Conveniently, the active ingredient comprises from 0.1-100% by weight of the formulation. Conveniently, a dosage unit of the formulation contains between 50 mg and 5000 mg, preferably between 200 mg and 1000 mg of a compound of formula I.

By the term "dosage unit" is meant a unitary, i.e. a single dose which is capable of being administered to a patient, and which may be readily handled and packed, remaining as a physically and chemically stable unit dose comprising either the active material as such or a mixture of it with solid or liquid pharmaceutical diluents or carriers.

The formulations include e.g. those in a form suitable for oral (including sustained or timed release), rectal, parenteral (including subcutaneous, intraperitoneal, intramuscular, intraarticular and intravenous), transdermal, ophthalmic, topical, nasal or buccal administration.

The formulations may conveniently be presented in dosage unit form and may be pre- pared by any of the methods well known in the art of pharmacy, e.g. as disclosed in Remington, The Science and Practice of Pharmacy. 20^th ed., 2000. All methods include the step of bringing the active ingredient into association with the carrier, which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing the active ingredient into association with a liquid carrier or a finely divided solid carrier or both, and then, if necessary, shaping the product into the desired formulation.

Formulations of the present invention suitable for oral administration may be in the form of discrete units as capsules, sachets, tablets or lozenges, each containing a prede- termined amount of the active ingredient; in the form of a powder or granules; in the form of a solution or a suspension in an aqueous liquid or non-aqueous liquid, such as ethanol or glycerol; or in the form of an oil-in-water emulsion or a water-in-oil emulsion. Such oils may be edible oils, such as e.g. cottonseed oil, sesame oil, coconut oil or peanut oil. Suitable dispersing or suspending agents for aqueous suspensions include synthetic or natural gums such as tragacanth, alginate, acacia, dextran, sodium carboxymethylcellulose, gelatin, methylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, carbomers and polyvinylpyrrolidone. The active ingredients may also be administered in the form of a bolus, electuary or paste.

A tablet may be made by compressing or moulding the active ingredient optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing, in a suitable machine, the active ingredient(s) in a free-flowing form such as a powder or granules, optionally mixed by a binder, such as e.g. lactose, glucose, starch, gelatine, acacia gum, tragacanth gum, sodium alginate, carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, polyethylene glycol, waxes or the like; a lubricant such as e.g. sodium oleate, sodium stearate, magnesium stearate, sodium benzoate, sodium acetate, sodium chloride or the like; a disintegrating agent such as e.g. starch, methylcellulose, agar, bentonite, croscarmellose sodium, sodium starch glycollate, crospovidone or the like or a dispersing agent, such as polysorbate 80. Moulded tablets may be made by moulding, in a suitable machine, a mixture of the powdered active ingredient and suitable carrier moistened with an inert liquid diluent. Formulations for rectal administration may be may in the form of suppositories in which the compound of the present invention is admixed with low melting water soluble or insoluble solids such as cocoa butter, hydrogenated vegetable oils, polyethylene glycol or fatty acids esters of polyethylene glycols, while elixirs may be prepared using myristyl palmitate.

Formulations suitable for parenteral administration conveniently comprise a sterile oily or aqueous preparation of the active ingredients, which is preferably isotonic with the blood of the recipient, e.g. isotonic saline, isotonic glucose solution or buffer solution. The formulation may be conveniently sterilised by for instance filtration through a bacteria retaining filter, addition of sterilising agent to the formulation, irradiation of the formulation or heating of the formulation. Liposomal formulations as disclosed in e.g. Encyclopedia of Pharmaceutical Technology, vol.9, 1994, are also suitable for parenteral administration.

Alternatively, the compound of formula I may be presented as a sterile, solid preparation, e.g. a freeze-dried powder, which is readily dissolved in a sterile solvent immediately prior to use.

Transdermal formulations may be in the form of a plaster or a patch.

Formulations suitable ophthalmic administration may be in the form of a sterile aqueous preparation of the active ingredients, which may be in microcrystalline form, for example, in the form of an aqueous microcrystalline suspension. Liposomal formulations or biodegradable polymer systems e.g. as disclosed in Encyclopedia of Pharmaceutical Tehcnology, vol.2, 1989, may also be used to present the active ingredient for ophthalmic administration.

Formulations suitable for topical or ophthalmic administration include liquid or semi-liquid preparations such as liniments, lotions, gels, applicants, oil-in-water or water-in-oil emulsions such as creams, ointments or pastes; or solutions or suspensions such as drops.

Formulations suitable for nasal or buccal administration include powder, self-propelling and spray formulations, such as aerosols and atomisers. Such formulations are disclosed in greater detail in e.g. Modern Pharmaceutics, 2^nd ed., G.S. Banker and CT. Rhodes (Eds.), page 427-432, Marcel Dekker, New York; Modern Pharmaceutics, 3^th ed., G.S. Banker and CT. Rhodes (Eds.), page 618-619 and 718-721, Marcel Dekker, New York and Encyclopedia of Pharmaceutical Technology vol. 10, J Swarbrick and J.C. Boylan (Eds), page 191-221Marcel Dekker, New York

Active transport forms of the present invention may also be delivered by use of monoclonale antibodies as individual carriers to which the compound molecules are coupled.

In addition to the aforementioned ingredients, the formulations of a compound of formula I may include one or more additional ingredients such as diluents, buffers, flavouring agents, colourant, surface active agents, thickeners, preservatives, e.g. methyl hydroxybenzoate (including anti-oxidants), emulsifying agents and the like.

As described above, quorum sensing inhibitors will prevent the formation of persistent biofilm, which will make a bacterium more receptive to treatment with antibiotics. It is thus expected that the combination in a pharmaceutical composition of quorum sensing inhibitors and other types of antibiotics will exert a synergistic effect. Accordingly, in a preferred embodiment, the other therapeutically active compound optionally present in the formulation comprising a compound of formula I is selected from the group consisting of penicillins, e.g. selexcid, cephalosporins, tetracyclines, rifamycins, gentamycin, clindamycin, fluoroquinolones, monobactames, carbapenemes, macrolides, polymyxines, aminoglycosides, e.g. tobramycin, sulfonamides, fusidines, vancomycines, oxazolidinones and metronidazoles. Other compounds which advantageously may be combined with the compounds of the invention, especially in topical preparations, include e.g. corticosteroids, such as hydrocortisone, triamcinolone or betamethansone.

As noted above, the existence of quorum sensing systems is not exclusive to Pseudomonas aeruginosa. A wide range of bacteria also have a quorum sensing system homologues to that of Vibrio fischeri, i.e. a system homologues to the LuxR/LuxI system described above. Eberl, System. Appl. Microbiol., 22, 493, 1999, Gray and Garey, Microbiology, 147, 2379, 2001, disclose that the following bacteria have a quorum sensing system: Aeromonas hydrophila, Aeromonas salmonicida, Agrobacterium tumefaciens, Burkholderia cepacia, Chromobacterium violaceum, Enterobacter agglomerans, Erwinia carotovora, Erwinia chrysanthemi, Pantoea stewartii subsp. stewartii, Pseudomonas aeruginosa, Pseudomonas aureofaciens, Pseudomonas fluorescens, Pseudomonas syringae, Ralstonia solanacearum, Rhizobium etli, Rhizobium leguminosarum, Rhodobacter sphaeroides, Serratia liquefaciens, Serratia marcescens, Vibrio anguillarum, Yersinia enterocolitica, Yersinia pseudotuberculosis, and Yersinia ruckeri, of which several are known human, animal or plant pathogens. As evidenced by this list, quorum sensing is wide spread in nature, and it is thus believed that therapeutical compositions comprising quorum sensing inhibitors, and in particular compounds of the present invention, optionally in combination with other therapeutically active compounds, are generally useful in the treatment of infections.

The present invention therefore also provides a method of treating infections in humans or animals, the method comprising administering to said human or animal an effective amount of a compound of formula I, optionally together with another therapeutically active ingredient. Preferably, the infection is a bacterial infection, e.g. a Pseudomonas aeruginosa infection, e.g. on burns, on implants or in the lungs, e.g. of patients with cystic fibrosis.

Patients suffering from cystic fibrosis have a very high risk of being infected by

Pseudomonas aeruginosa in the lungs. Administration of a quorum sensing inhibitor of the present invention will prevent the formation of persistent Pseudomonas aeruginosa biofilms in the lungs of the patients and will improve the chances of the defence system of the patient itself to clear the lungs of Pseudomonas aeruginosa. The invention thus also relates to a method of preventing cystic fibrosis patients from being infected with Pseudomonas aeruginosa, the method comprising administering to said patient an effective amount of a compound of formula I.

In the systemic treatment using the present invention daily doses of from 0.1-100 mg per kilogram body weight, preferably from 0.5-50 mg/kg of mammal body weight, for example 1-10 mg/kg of a compound of formula I is administered, typically corresponding to a daily dose for an adult human of from 0.1 to 10 g. In the topical treatment of dermatological disorders, ointments, creams or lotions containing from 0.1-1000 mg/g, and preferably from 0.1-500 μg/g, for example 0.1-200 μg/g of a compound of formula I is administered. For topical use in ophthalmology ointments, drops or gels containing from 0.1-1000 mg/g, and preferably from 0.1-500 mg/g, for example 0.1-100 mg/g of a compound of formula I is administered. The oral compositions are formulated, preferably as tablets, capsules, or drops, containing from 0.07-1000 mg, preferably from 0.1-500 mg, of a compound of formula I per dosage unit. It is recommended to consult "Goodman & Gilman's The pharmacological basis of therapeutics" 9^th edition,

J.G.Hardman and L.E Limbird (Eds. in chief), McGraw-Hill, New York, 1996 for relevant doses of the other therapeutically active compounds. The present invention also relates to the use of a compound of formula I in the preparation of a medicament for the treatment or prevention of infections, in particular bacterial infections. Particular preferred in this embodiment is infections caused by Pseudomonas aeruginosa in the lungs, on implants or on burns. It is believed that compounds of formula I are particular well-suited to be used in the manufacture of medicaments for the treatment or prevention of Pseudomonas aeruginosa infections in the lungs of cystic fibrosis patients. As described above, other therapeutically active compounds, such as penicillins, e.g. selexcid, cephalosporins, tetracyclines, rifamycins, gentamycin, clindamycin, fluoroquinolones, monobactamer, carbapenemer, macrolider, polymyxiner, aminoglycosider, e.g. tobramycin, sulfonamides, fusidines, vancomycines, oxazolidinones, metronidazoles and corticosteroids, such as hydrocortisone, triamcinolone or betamethasone may be included in the medicament, too.

It is well-known that endoprostheses implanted in blood vessels or otherwise in contact with a human or animal body are easily infected by bacteria and that these bacteria often grow as biofilms. The infections are thus often difficult to treat and, combined with the fact that patients with endoprostheses are often severely debilitated, makes said infections potentially lethal. Endoprostheses includes catheters, stents, pacemakers, heart valves, implants etc. The use of compounds and compositions of the present invention in the treatment of infections has been discussed above, but it is further envisaged that endoprostheses may be impregnated with compounds of the present invention to prevent infections, e.g. as disclosed in US5,902,283 and US5,562,704.

The invention also provides a method of controlling bacterial growth, e.g. in water system, such as cooling or fresh water systems. Said method comprises contacting said bacteria with a compound according to formula I, optionally in combination with a bacteriostatic or bacteriocidal compound.

General methods of synthesis

The compounds of the present invention can be prepared in a number of ways well known to those skilled in the art of organic synthesis. The compounds of the present invention can be synthesized using the methods outlined below, together with methods known in the art of synthetic organic chemistry, or variations thereof as appreciated by those skilled in the art. Preferred methods include, but are not limited to, those described below.

The novel compounds of the general formula may be prepared using the reactions and techniques described in this section. The reactions are performed in solvents appropriate to the reagents and materials employed and suitable for the transformations being effected. Also, in the synthetic methods described below, it is to be understood that all proposed reaction conditions, including choice of solvent, reaction atmosphere, reaction temperature, duration of experiment and work-up procedures, are chosen to be conditions of standard for that reaction, which should be readily recognized by one skilled in the art. It is understood by one skilled in the art of organic synthesis that the functionality present on various portions of the educt molecule must be compatible with the reagents and reactions proposed. Not all compounds of the general formula falling into a given class may be compatible with some of the reaction conditions required in some of the methods described. Such restrictions to the substituents, which are compatible with the reaction conditions, will be readily apparent to one skilled in the art and alternate methods can be used.

Compounds according to the present invention comprise a sulfonamide linkage. The condensation is carried out using any of the many methods for the formation of sulfonamide linkages known to one skilled in the art of organic synthesis as described in standard chemistry textbooks such as March's Advanced Organic Chemistry (Michael B. Smith and Jerry March, 5. Ed. 2001, Wiley Interscience, New York). Such can typically be established by reaction between a sulfonyl halide and an amine under Schotten-Bauman type conditions (aqueous base), or in the presence of other bases such as tertiary amines (DIEA or triethylamine). Sulfonyl halides such as fluorides, chlorides, bromides or iodides are frequently commercially available or can be prepared by standard operations from the corresponding sulfonic acids or the corresponding salts, typically sodium salt. Methods for the conversion of such sulfonic acids or salts to the corresponding sulfonyl halides are apparent to one skilled in the art and can typically be mediated by reagents such as thionyl chloride (SOCI₂, Organic Synthesis, Collective Volume IV, 571-572) or phorphorus pentachloride (PCI₅, Organic Synthesis, Collective Volume IV, 846-851 and Collective Volume V, 196-199), phorphorus oxychloride (POCI₃, Organic Synthesis, Collective Volume I, 84-87) or equivalent reagents.

In case the sulfonic halides or sulfonic acids are not commercially available, these compounds can be prepared by a variety of methods known to those skilled in the art. These methodologies comprise the conversion of alkylmercaptans to sulfonyl chloride by chlorine oxidation (I. B. Douglass and T. B. Johnson, J. Am. Chem. Soc. 1938, 1486- 1489) or from an alkyl halide by treatment with sodium sulfite to the corresponding sulfonic acid (L.K.J. Tong, J. Am. Chem. Soc, 1959, 82, 1988). Likewise, substituted mercaptanes can be prepared by nucleophilic ring-opening reactions of epoxides with hydrogen sulfide (F. Berbe (1950) Bull. Soc. Chim. Belg. 59, 449-464) or the corresponding sulfonic acid by ring-opening with sodium sulfite or an equivalent reagent. Thus, it is obvious for those skilled in the art, that alkyl halides, mercaptanes and equivalent reagents are readily available either commercially or by standard chemical preparations.

In special cases where functional groups present in RI, R2 or in the ring structure of formula I are not compatible with the reaction conditions required for coupling sulfonyl halides or sulfonic acids as described above, these functionalities may be protected temporarily with a protecting group well known to one skilled in the art as described in standard chemistry textbooks such as Greene's Protective Groups in Organic Chemistry (Theodora W. Greene and Peter G. M. Wuts, 3. Ed. 1999, Wiley Interscience, New York). Alternatively, sulfonamides can be formed under mild conditions by the reaction between an amine and the corresponding lAY-benzotriazol-l-yl sulfonate (HOBt-sulfonate, S. Y. Kim et al., Tetrahedron Lett. 40 (1999) 117-120), the corresponding Λ/-benzotriazolide (A. L. Katritsky et al. Synthetic Commun. 24 (1994) 205-216 and references cited therein), the corresponding ΛHmidazolide (J. F. O'Connell and H. Rapoport, J. Org. Chem. 57 (1992) 4775-4777) or equivalent leaving groups familiar to those skilled in the art of organic synthesis.

Compounds according to the present invention comprise a sulfonamide linkage to the ring structure. In a preferred embodiment, the ring structure includes D- and L- homoserine lactones, which are commercially available or can be synthesized from the corresponding methionine (S. R. Angle and R. M. Henry, J. Org. Chem. 63 (1998) 7490- 7497) or aspartic acid derivatives (H. C. Uzar, Synthesis 1991, 526-528). Similarly, homocysteine thiolactone is commercially available and can be acylated as an unmodified lactone (J. A. Robl et al., J. Med Chem. 40 (1997) 1570-1577) as well as sulfonated under standard conditions (H. Meguro et al., Tetrahedron Lett. 1972, 3165- 3168). The homoserine lactam (3-amino-pyrrolidin-2-one) can be synthesized by several, well-established procedures (S. Wilkinson, J. Chem. Soc. 1951, 104-108; R. Pellegata et al. Synthesis 1978, 614-616). Generally, thioamides are obtained by standard reactions including phosphorus pentasulfide (P₄Oι₀), Lawesson's reagent (2,4- bis(4-methoxyphenyl)-l,3,2,4-dithiaphosphetane-2,4-disulfide, by thiolysis of iminium triflates (A. B. Charette and P. Chua, Tetrahedron Lett. 39 (1998) 245-248), or the like. In addition, dithiocarboxylic esters and lactones are prepared in a similar way (Michael B. Smith and Jerry March, March's Advanced Organic Chemistry 5. Ed. 2001, Wiley Interscience, New York and references cited therein).

Alkylation of ring nitrogens such as in lactams and thiolactam ring systems may be performed by a series of methods well-known by those skilled in the art including reductive alkylations, direct alkylation by alkyl halides or triflates or the like (W. R. Ewing et al. J. Med. Chem. 42 (1999) 3557-3571; Y. M. Choi-Sledeski et al. Bioorg. Med. Chem. Lett. 9 (1999) 2539-2544).

5-substituted homoserine lactones can be synthesized by a range of different methods including cycloaddition by cyclic nitrones with allyl alcohol followed by Pd(OH)₂ mediated hydrogenolysis and simultaneous reductive N-0 and N-benzyl cleavages followed by lactonization (Tamura, O. et al. (1999) Tetrahedron Lett. 40, 895-898). Alternatively, the synthesis from isopropylidine-protected D-xylose, D-ribonolactone or similar carbohydrate or carbohydrate-like derivatives (Debernado et al. (1985) J. Org. Chem. 50, 3457-3462; J. Ariza et al. Tetrahedron Lett. (1991) 32, 1979-1982) or by Os0₄- mediate dihydroxylation of appropriately protected allylglycine, such as Boc-allylglycin (A. Girard et al. Tetrahedron Lett. (1998) 39, 4259-4260).

Similarly, 4-substituted homoserine lactones can be synthesized by a range of different methods including carbohydrate derivatives such as appropriately protected glyceraldehyde (M. Sendai et al. (1985) Chem. Pharm. Bull. 33, 3798-3810) or hydroxy- bromo-lactones (M. Bols and I. Lundt (1988) Acta Chem. Scand. B42, 67-74).

Alternatively, 4-modification can be introduced by Os0 -mediated dihydroxylation of appropriately protected vinylglycine, such as Boc-vinylglycin (J. A. Olsen et al. (2002) Bioorg. Med. Chem. Lett. 12, 325-328). The 4- and 5-modified substituent can then be modified further by alkylations, acylations, carbamoylation or by other appropriate FGI (Functional Group Interconversion) such as reductions, oxidations, epoxidations, saponifications, decarboxylations, etc. well-known to those skilled in the art of organic synthesis (J. A. Olsen et al. (2002) Bioorg. Med. Chem. Lett. 12, 325-328).

Sulfonic acids carrying ramified substituents may be synthesized by a series of standard chemical transformation familiar to those skilled in the art and covered in many general synthetic organic text books (Organic Synthesis, M. B. Smith 1994, McGraw-Hill, New York; The Logic of Chemical Synthesis, E. J. Corey and X.-M. Cheng, 1995 John Wiley & Sons, New York; Classics in Total Synthesis, K. C. Nicolaou and E. J. Sorensen, 1996, VCH, Weinheirn; March's Advanced Organic Chemistry, Michael B. Smith and Jerry March, 5. Ed. 2001, Wiley Interscience, New York). Examples thereof include homologation by C-alkylation of activated carbons such as benzylic positions (Bunce, R. A. and Sullivan, J. P. (1990) Synth. Comm. 20, 865-868), the coupling of Grignard reagents with organic halides (M. Tamura and J. Kochi (1971) Synthesis, 303-305), by alkylation of organometalics and related compounds by sultones (Truce, W. E. and Hoerger, F. D. (1955) J. Am. Chem. Soc. 77, 2496-2500) or by nucleophilic ring-opening of sultones (Dillard, R. D. et al. (1996) J. Med. Chem. 39, 5137-5158). Many other methodologies can be applied including carbon-carbon forming reactions such as the

Wittig-reaction, Peterson Olefination, Horner-Wadsworth-Emmons reactions, Diels-Alder reactions, Claisen-condensation, Michael additions, Aldol condensation, Suzuki couplings, Stille couplings and Heck couplings, either directly or followed by the appropriate FGI (Functional Group Interconversion) such as reductions, oxidations, epoxidations, saponifications, decarboxylations, etc. well-known to those skilled in the art of organic synthesis.

Examples For each compound, ^JH NMR and ¹³C NMR spectra were recorded using a Varian Unity Inova 500 MHz spectrometer (operating at 499.87MHz) or a Varian Mercury 300 spectrometer. The solvent signal in each spectrum was used as internal reference. A Perkin Elmer 1720 Fourier Transform spectrometer was used for IR measurements. Melting points are uncorrected. Optical rotation was measured on a Perkin Elmer 241 polarimeter. RP-HPLC purification was performed on a Waters 600 C18 equipped with a reverse-phase column with a CH₃CN/H 0 gradient as eluent. Unless otherwise stated the material used for column chromatography (cc) purification was Merck Si0₂ 60, mesh 230-400. Tetrahydrofuran (THF) and diethyl ether (Et₂0) was distilled over sodium- benzophenone immediately prior to use. In case dichloromethane (DCM) and triethylamine (TEA), distilled over CaH and DMF, distilled over BaO, were not used immediately, they were kept over 4 A molecular sieves (MS). Diphenylmethane and 1,5- dibromopentane were distilled prior to use and stored over 4 A MS. All reagents, unless otherwise noted, were purchased from Aldrich Chemical Co. Horizon: Biotage Automatic flash chromatograph equipped with an UV detector, fraction collector, and a gradient module capable of mixing a two-component gradient. Stationary phase of silica gel columns. HPLC: Waters Alliance Separation Module 2795 and 2996 PDA detector using Waters SymmetryShield or XTerra RP columns and acetonitrile-water gradients. MS: Electron impact (EI⁺). HRMS: Electro spray (ES⁺). HSL: Abbreviation for homoserine lactone.

Preparation 1 L-Homoserine lactone hydrobromide

L-methionin (15.22g; 102mmol) was added to a solution of H₂0 (60mL), 2-propanol (60mL), and glacial acetic acid (24mL; 99%). The solution was stirred until homogeneity, bromoacetic acid (14.3g; 103mmol) was added, and the reaction mixture refluxed for 2 hrs. The reaction mixture was cooled to room temperature and concentrated to a viscous orange oil. A solution of 2-propanol and toluene (lOmL, 1 : 1 v/v) was added and the reaction mixture was stirred until homogeneity. Concentration (bath temperature: 90°C) afforded an orange oil. A solution of dioxane (40mL) and concentrated HCl (20mL) was added to the orange oil, and the resulting solution was heated to 50°C for 10 min. The heating bath was removed, the mixture was stirred over night, and the reaction flask was placed in an ice bath for 4 h without stirring to precipitate an orange solid. The orange solid was filtered and rinsed with cold 2-propanol (25mL; -78°C) until the rinsings were colourless. The resulting white solid was dried (0.5mmHg) to afford the title product, mp 226-230°C, [α]_D = -25,3° (c = 8,7 mg/10 mL; H₂0).

Preparation 2

1-Pentanesulfonyl chloride

Dry sodium 1-pentane sulfonate (l,26g; 7.2mmol) and PCI₅ (1.5g; 7.2mmol) was mixed and the solution was heated (oil bath temperature: 140°C) for 45 min. with reflux condenser. The reaction mixture was cooled, and dry toluene (20mL) was added. While stirring well, the mixture was heated (oil bath temperature: 110°C) for 5 min. The reaction mixture was filtered and then concentrated. The resulting oil was distilled (95- 105°C; 12mmHg) to afford the title compound.

Preparation 3

1-Hexanesulfonyl chloride

H₂0 (lOOOmL) and hexanethiol (20mL; 16.8g; 142mmol) was mixed in a three-necked flask with stirring. The mixture was cooled to 5°C and Cl₂ was slowly bubbled through the mixture for 6 h, while the temperature was kept below 10°C. The reaction mixture was neutralized with saturated NaHC0₃ and the product was extracted with ether

(200mL). The remaining water was washed with ether (50mL). The combined organic layers were dried with Na₂S0₄ and concentrated to a colourless oil which was distilled. The product was unstable when exposed to heat, and therefore difficult to distil. Most impurities were removed by distillation (65°C, 0.4mmHg). The crude product was used for further synthesis.

Preparation 4

1-Heptanesulfonyl chloride

Dry sodium 1-heptan sulfonate (1.50g; 6.81mmol) and PCI₅ (1.6g; 7.7mmol) was mixed and the solution was heated (oil bath temperature: 140°C) for 45 min. with reflux condenser. The reaction mixture was cooled, and dry toluene (20mL) was added. While stirring well the mixture was heated (oil bath temperature: 110°C) for 5 min. The reaction mixture was filtered and then concentrated. The resulting oil was distilled (129- 131°C, 15mmHg) to afford the product.

Preparation 5 Sodium 2-oxo-propanesulfonate

Chloroacetone (9.253g; O.lOmol), Na₂S0₃ (14.5g; 11.5mmol) and H₂0 (100 mL) were mixed in a flask fitted with a condenser. The mixture was refluxed with stirring for 24 hrs, after which the mixture was evaporated to dryness. The residue was dissolved in boiling ethanol and filtered to yield the title compound after evaporation of solvent, mp: 173 - 180 °C.

Preparation 6

2-Oxo-propanesulfonyl chloride

Preparation 5 (1.38 g; 7.6 mmol) was suspended in toluene (5 mL) and POCI₃ (5 mL) was added while stirring. The mixture was fitted with a reflux condenser and heated (oil bath 110°C) for 3 hrs. The solvent was removed by evaporation, and the product was dissolved in DCM (lOmL) and the mixture was filtered. The residue was concentrated to yield the title compound, which was used without further purification. H NMR (CDCI₃); δ:

4.73, 2.48. ¹³C NMR; δ: 192.6, 73.2, 30.5.

Preparation 7 l-Bromo-6,6-diphenylhexane

A solution of diphenylmethane (8.40 mL, 50.0 mmol) in THF (150 mL) under argon turned darkly red when inserting 1.6 M n-BuLi (3.20 mL, 51.0mmol). The solution was stirred for 15 min. and then transferred, drop-wise, with a syringe, to another solution under inert atmosphere, consisting of 1,5-dibromopentane (6.75 mL, 50 mmol) dissolved in THF (300 mL) cooled to -78°C. After complete addition of the lithiate, the resulting mixture was allowed to warm slowly to room temperature. The reaction was quenched after another 22 hrs of stirring by pouring the mixture into 300 mL of water. Extraction (ether), washing (H₂0 and brine), drying (MgS0₄) and filtration afforded a yellow oil when removing the solvent. Purification by column chromatography (Si0₂, 0=8 cm, H=19 cm; eluent: hexane) afforded the title compound. *H NMR (500 MHz, CDCI₃) δ: 7.31-7.15, 3.91, 3.38, 2.08, 1.84, 1.49, 1.31. ¹³C NMR (125 MHz, CDCI₃) δ: 145.06, 128.41, 127.82, 126.09, 51.32, 35.64, 33.81, 32.64, 28.14, 27.18.

Preparation 8 l-Bromo-6,6-dimethylheptane

A catalyst was prepared in situ by mixing CuCI₂ (20 mg, 0.15 mmol) and LiCI (13 mg, 0.30 mmol) in a separate flask and evacuating it (vacuum-pump). After a while in vacuum it was filled with argon and then THF (1.5 ml) was added. The orange solution formed was added with a syringe to a solution of 1,5-dibromopentane in THF (20 mL) cooled to 0°C. Then a 1.0 M solution of t-BuMgCI (6.0 mL, 6.0 mmol) was added drop- wise over a period of one hour from a dropping-funnel. The mixture gradually turned darker until totally black. After 6V2 hrs of stirring it was poured into water to quench the reaction. A Cu-mirror was seen on the flask wall. The colorless oil remaining after extraction (3x50 mL ether), washing of the combined organic phases (2x50 mL H₂0), drying (MgS0₄), filtration and evaporation to dryness, was purified by column chromatography (Brockman Type I Al₂0₃, 0=3 cm, H=13 cm; eluent: Hexane) to provide the title compound. ^XH NMR (500 MHz, CDCI₃) δ: 3.41, 1.87, 1.40, 1.31-1.23, 1.17, 0.87. ¹³C NMR (125 MHz, CDCI₃) δ: 44.02, 33.98, 32.91, 30.28, 29.34, 29.12, 23.77.

Preparation 9

3-Phenylpropane-l-sulfonic acid

To a 1.0 M solution of phenyl magnesium chloride in THF (2.0 mL, 2.0 mmol) under argon was added 1,3-propane sultone (136 mg, 1.0 mmol) in one portion. The temperature was raised from ambient to reflux on oil-bath and the mixture turned yellow but still clear. 22 hrs of reflux and stirring resulted in a more viscous, almost semi-solid, yellow and clear mixture. The reaction was quenched by adding 1 M HCl until pH ~2 and then removal of solvent afforded an orange oily crude product, subsequently purified by flash chromatography (flash-collector: Biotage; Si0₂; eluent: 4 % MeOH in DCM) to afford the title compound. IR (neat) : 3398, 1656, 1497, 1454, 1200, 1087 cm^"1. *H NMR (300 MHz, CDCI₃) δ: 7.28-7.15, 2.81, 2.74, 2.10.

Preparation 10 3-Phenylbutane-l-sulfonic acid

Under argon and at room temperature 1,3-propane sultone (111 mg, 0.91 mmol) was added to a 1.0 M ether-solution (1.0 mL, 1.0 mmol) of benzyl magnesium chloride. The mixture was kept at that temperature for 5 hrs and then quenched with water. Phase- separation and successive ion-pair-exchange by running the water-phase through amberlite-120 (1.9 meq/mL, Fluka BDH) resulted in a white solid crude product. It was dissolved in least amount of MeOH and put on a Si0₂-column for flash chromatography purification (flash-collector: Biotage; Si0₂; eluent: 4 % MeOH in DCM) to afford the title compound. IR (neat) = 3412, 1658, 1496, 1454, 1219, 1185, 1067 cm^"1. ^XH NMR (300 MHz, CDCI₃) δ: 7.28-7.15, 2.85, 2.65, 1.83-1.74.

Preparation 11

3-Phenylpentane-l-sulfonic acid

To a 1.0 M solution of benzyl magnesium chloride in THF (2.0 mL, 2.0 mmol) under argon was added 1,4-butane sultone (0.10 mL, 1.0 mmol) in one portion. The temperature was then raised from ambient to reflux on oil-bath and a white precipitate appeared. Reflux and stirring for 21 hrs was ended with quenching the reaction adding 1 M HCl until all solid had dissolved (pH ~2). Separation of the aqueous phase from the organic and evaporation of the former to dryness provided an off-white solid, which was dissolved in least amount of MeOH and put on a Si0₂-column for flash chromatography purification (flash-collector: Biotage; Si0₂; eluent: 4 % MeOH in DCM) to yield the title compound. ^X NMR (300 MHz, CDCI₃) δ: 7.22-7.04, 2.81, 2.60, 1.87-1.77, 1.64.

Preparation 12 3-Benzyloxypropane-l-sulfonic acid (sodium salt)

Benzyl alcohol (207 μL, 2.0 mmol) was inserted in a flask purged with argon containing a suspension of NaH (60% in mineral oil, 80 mg, 2.0 mmol) in THF (15 mL). A white solid appeared while gas was evolving and after half an hour of stirring at room temperature 1,3-propane sultone (136 mg, 1.0 mmol) was added in one portion. Reflux overnight made the mixture turn slightly yellow. The solvent was removed in vacuum and the white solid residue was dissolved in the least amount of a 1 :9 mixture of MeOH/DCM. Flash chromatography (flash-collector: Biotage; Si0₂; eluent: 4 % MeOH in DCM) yielded the title compound. IR (neat)=3437 (br), 1455, 1221, 1190, 1065 cm^"1. ^λ NMR (500 MHz, MeOD) δ: 7.32-7.23, 4.50, 3.59, 2.88, 2.10-2.04. ¹³C NMR (125 MHz, MeOD) δ: 139.87, 129.32, 128.79, 128.56, 73.77, 69.99, 49.76, 26.59.

Preparation 13 6,6-Diphenylhexane-l-sulfonic acid (sodium salt .

An aqueous solution (36 mL) of Na₂S0₃ (0.70 g, 5.5 mmol) was added over 12 h from a dropping-funnel to a boiling solution of preparation 7 (1.58 g, 5.0 mmol) dissolved in abs. EtOH (36 mL). At first the combined mixture appeared as opaque but at the end of the addition it was clear and homogeneous with the exception of the additive and a few drops of starting material found at the bottom due to the polar solvent. Na₂S0₃ (0.63 g, 5.0 mmol) was added to push the reaction further, and reflux continued for 2¹/₂ hrs. Removal of solvent in vacuum gave a white oily residue. It was partly dissolved in hexane to collect the title compound as a white solid upon filtration. IR (neat): 3441 (br), 1599, 1493, 1451, 1185 cm^"1. ^l NMR (500 MHz, CDCI₃/MeOD δ: 7.21-7.07, 3.81, 2.79, 1.98, 1.71, 1.38, 1.23. ¹³C NMR (125 MHz, CDCI₃/MeOD δ: 145. 73, 128.99, 128.40, 126.66, 52.17, 51.91, 36.05, 29.14, 28.22, 24.92

Preparation 14 6.6-Dimethylheptane-l-sulfonic acid

An aqueous solution (10 mL) of Na₂S0₃ (0.22 g, 1.76 mmol) was added over 15 h from a dropping-funnel to a boiling solution of preparation 8 (0.33 g, 1.60 mmol) dissolved in abs. EtOH (10 mL). It turned more and more opaque as addition was continued and at last, before removing the solvent, a white precipitate could be seen. The oily solid remaining after evaporation was dissolved in 1.0 M HCl (~5 mL, pH ~2) and another evaporation provided an orange/yellow solid, which was dissolved in EtOH. Filtration and evaporation of the filtrate afforded the title compound as an orange/yellow solid. ^XH NMR (500 MHz, D₂0) δ: 2.81, 1.65, 1.30, 1.21, 1.09, 0.77. ¹³C NMR (125 MHz, D₂0) δ: 51.81, 43.98, 30.07, 29.48, 29.40, 24.70, 24.12

Example 1

Λ/-Methanesulfonyl-L-homoserine lactone 12a

Preparation 1 (219.8mg; 1.21mmol) was suspended in DCM (5mL), and Et₃N (0.34mL;

2.4mmol) was added while stirring. The mixture was cooled to 0°C, and methanesulfonyl chloride (210 mg; 1.83 mmol) was added. The mixture was stirred for another 30 min. at 0°C. The reaction mixture was evaporated to dryness and the solid was dissolved in DCM (3mL) and flash chromatographed with the eluent hexan/EtOAc(l :4) to give the title compound, mp: 107-108°C. [α]_D (c = 9.75mg; lOmL DCM) = -48.21°. ^X NMR (D₂0) δ: 4.42, 4.35, 4.19, 3.05, 2.58, 2.13; ¹³C NMR δ: 177.9, 66.9, 52.0, 41.2, 29.5. IR (KBr) : 3258, 1766, 1354, 1144. Elemental analysis: Found (cal) : C: 33.91 (33.51); H : 4.82 (5.06); N : 7.68 (7.82) Example 2

Λ/-Ethanesulfonyl-L-homoserine lactone 12b

Preparation 1 (207.7mg; 1.14mmol) was suspended in DCM (5mL), and Et₃N (0.34mL; 2.4mmol) was added while stirring. The mixture was cooled to 0°C, and ethanesulfonyl chloride (255.0 mg; 1.98 mmol) was added. The mixture was stirred for another 30 min. at 0°C. The reaction mixture was evaporated to dryness and the solid was dissolved in DCM (3mL) and flash chromatographed with the eluent hexan/EtOAc (1 :2) to give the title compound; mp: 72-73°C. [ ]_D (c = 9.89mg; lOmL DCM) = -25.28°. ^JH NMR (CDCI₃) δ: 5.37, 5.29, 4.43, 4.36, 4.20, 3.22, 2.73, 2.29, 1.41. ¹³C NMR δ: 174.9, 65.6, 52.0, 48.7, 30.7, 8.1. IR (KBr): 3302, 1794, 1341, 1132 cm^"1.

Example 3 /-Propanesulfonyl-L-homoserine lactone la

Preparation 1 (192.8mg; 1.06mmol) was suspended in DCM (5mL), and Et₃N (0.31mL; 2.2mmol) was added while stirring. The mixture was cooled to 0°C, and 1- propanesulfonyl chloride (240.6mg; 1.68mmol) was added. The mixture was stirred for another 30 min. at 0°C. The reaction mixture was evaporated to dryness and the solid was dissolved in DCM (3mL) and flash chromatographed with the eluent hexan/EtOAc (1 : 1). to give the title compound, mp: 104-105°C. [α] (c = 9.28mg; lOmL DCM) = - 28.02°.^ NMR (CDCI₃) δ:6.54, 4.37, 4.25, 4.18, 3.08, 2,58, 2.13, 1.85. ¹³C NMR δ: 174.9, 65.3, 56.0, 51.6, 30.2, 17.0, 12.6. IR (KBr) : 3250, 1767, 1352, 1144 cm^"1. Elemental analysis: Found (cal) : C: 40.70 (40.57); H : 6.16 (6.32); N : 6.66 (6.76)

Example 4 Λ/-Butanesulfonyl-L-homoserine lactone lb

Preparation 1 (182. Omg; l.Ommol) was suspended in DCM (5mL), and Et₃N (0.31; 2.2mmol) was added while stirring. The mixture was cooled to 0°C, and 1-butanesulfonyl chloride (210mg; 1.34mmol) was added. The mixture was stirred for another 30 min. at 0°C. DCM (5mL) was added and the solution was washed with HCl (3%, lOmL), NaHC0₃ (5%, lOmL), and twice with NaCl (sat., lOmL). The organic layer was dried with Na₂S0₄, evaporated to dryness and the solid was dissolved in DCM (3mL) and flash chromatographed in the eluent hexan-EtOAc (3: 2) to give the title compound, mp: 76- 78°C. [α]_D (c = 9.13mg; lOmL DCM) = -21.14°.^ NMR (CDCI₃) δ: 5.47, 4.41, 4.33, 4.26, 3.16, 2.68, 2.28, 1.8, 0.92. ¹³C NMR δ: 175.0, 65.5, 54.0, 51.9, 30.4, 25.2, 21.2, 13.4; IR (KBr) : 3258, 1766, 1354, 1144 cm^"1.

Example 5 Λ/-Pentanesulfonyl-L-homoserine lactone 12c

Preparation 1 (222. Omg; 1.22mmol) was suspended in DCM (5mL), and Et₃N (0.34mL; 2.4mmol) was added while stirring. The mixture was cooled to 0°C, and preparation 2 (191. Omg; 1.12mmol) was added. The mixture was stirred for another 30 min. at 0°C. DCM (5mL) was added and the solution was washed with HCl (3%, lOmL), NaHC0₃ (5%, lOmL), and twice with NaCl (sat., lOmL). The organic layer was dried with Na₂S0₄, evaporated to dryness and the solid was dissolved in DCM (3mL) and flash chromatographed in the eluent hexan-EtOAc (3:2) to give the title compound; mp: 47- 49°C. [α]_D (c = 11.03mg; lOmL DCM) = -14.51°. ^:H NMR (CDCI₃) δ: 5.41, 4.43, 4.33, 4.24, 3.36, 2.70, 2.28, 1.95-1.70, 1.50-1.20, 0.88. ¹³C NMR δ: 174.9, 65.5, 54.3, 52.0, 30.6, 30.1, 23.0, 22.0, 13.6. IR (KBr) : 3264, 1778, 1326, 1140 cm^"1. Elemental analysis: Found (cal) : C: 45.96 (45.93); H: 7.20 (7.28); N: 5.82 (5.98).

Example 6 Λ/-Hexanesulfonyl-L-homoserine lactone lc

Preparation 1 (199.3mg; 1.09mmol) was suspended in DCM (5mL), and Et₃N (0.31mL; 2.2mmol) was added while stirring. The mixture was cooled to 0°C, and crude preparation 3 (367mg; 1.99mmol) was added. The mixture was stirred for another 30 min. at 0°C. The reaction mixture was evaporated, to dryness and the solid was dissolved in DCM (3mL) and flash chromatographed in the eluent hexan/EtOAc (2: 1) to give the title compound; mp: 47°C. ^XH NMR (CDCI₃) δ: 5.42, 4.42, 4.33, 4.24, 3.17, 2.32, 1.90-1.70, 1.5-1.2, 0.88. ¹³C NMR δ: 174.9, 65.5, 54.4, 52.0, 31.0, 30.6, 27.7,

23.3, 22.2, 13.8.

Example 7

Λ/-Heptanesulfonyl-L-homoserine lactone Id

Preparation 1 (185.0mg; 1.02mmol) was suspended in DCM (5mL), and Et₃N (0.31mL; 2.2mmol) was added while stirring. The mixture was cooled to 0°C, and preparations (290 mg; 1.46 mmol) was added. The mixture was stirred for another 30 min. at 0°C. DCM (5mL) was added and the solution was washed with HCl (3%, lOmL), NaHC0₃ (5%, lOmL), and twice with NaCl (sat., lOmL). The organic layer was dried with Na₂S0₄, evaporated to dryness and the solid was dissolved in DCM (3mL) and flash chromatographed in the eluent hexan-EtOAc (2: 1) to give the title compound; mp: 49- 50°C. [α]_D (c = 10.40mg; lOmL DCM) = -14.42°. ^XH NMR (CDCI₃) δ: 5.20, 4.45, 4.34, 4.26, 3.18, 2.28, 1.85, 0.88. ¹³C NMR δ: 174.7, 65.5, 54.4, 52.0, 31.4, 30.9, 28.6, 28.1,

23.4, 22.4, 13.9. IR (KBr) : 3254, 1778, 1314, 1139 cm^"1. Elemental analysis: Found (cal) : C: 50.27 (50.17); H : 8.02 (8.04); N : 5.27 (5.32). Example 8

■V-(2-Oxo-propanesulfonyl --L-homoserine lactone 12d

Preparation 1 (100.9mg; 0.55mmol) was dissolved in DCM (5mL) and Et₃N (0.17mL; 1.2mmol) was added while stirring. The mixture was cooled to 0 °C and crude preparation 6 (163mg; 1.04mmol) was added and the reaction mixture was kept at 0 °C for another 30 min.. The mixture was evaporated to dryness and the solid was dissolved in DCM (2mL) and flash chromatografed with the eluent EtOAc: hexane (2:3) to give the title compound; mp: 47°C. ^XH NMR (DMSO); δ: 8.1-8.0, 4.6-4.1, 4.41, 2.6-2.4, 2.25- 1.95, 2.27. ¹³C NMR; δ: 197.8, 175.3, 65.4, 65.1, 51.7, 30.6, 29.4.

Example 9

■V-(3-Phenylpropane-l-sulfonyl)-L-homoserine lactone 12e

A suspension of preparation 9 (33 mg, 0.16 mmol) in SOCI₂ (120 μL, 1.65 mmol) under argon with a catalytic amount of DMF (1 μL, 0.016 mmol) was heated close to reflux while stirring for 3 hrs to yield an oil after the solvent was removed. It was dissolved in DCM (1 mL) and transferred drop-wise via syringe to preparation 1 (26.5 mg, 0.15 mmol) dissolved by NEt₃ (43 μL, 0.31 mmol) in DCM (2 mL). The addition was made at 0°C and under argon and took Vi hour. After 4 hrs of stirring the reaction mixture was allowed to warm to ambient temperature and then left overnight. Quenching (H₂0) the reaction followed by extraction (3x10 mL EtOAc), washing the combined organic phases with H₂0, drying (MgS0₄) and filtration provided a crude product that was purified by flash-chromatography (flash-collector: Biotage; Si0₂; eluent: 2% MeOH in DCM) to yield the title compound. mp=73-75 °C; IR (neat)=3348, 1782, 1315, 1148 cm^"1. ^:H NMR (500 MHz, CDCI₃) δ: 7.32-7.19, 4.69, 4.43, 4.29-4.21, 3.16, 2.78, 2.75-2.70, 2.25-2.15. ¹³C NMR (125 MHz, CDCI₃) δ: 174.36, 140.00, 128.64, 128.48, 126.45, 65.59, 53.46, 52.12, 34.03, 31.30, 24.15.

Example 10 Λ/-(4-Phenylbutane-l-sulfonyl)-L-homoserine lactone 12f

A suspension of preparation 10 (14 mg, 0.059 mmol) in SOCI₂ (47 μL, 0.65 mmol) under argon with a catalytic amount of DMF (~1 μL) was heated close to reflux while stirring for 3 hrs to yield an oil after the solvent was removed. It was dissolved in DCM (1 mL) and transferred drop-wise via syringe to preparation 1 (9.8 mg, 0.054 mmol) dissolved by NEt₃ (16 μL, 0.31 mmol) in DCM (1 mL). The addition was made at 0°C and under argon and took Vi hour. After 3 hrs of stirring the reaction mixture was allowed to warm to ambient temperature and then left overnight. Quenching (H₂0) the reaction followed by extraction (3x30 mL EtOAc), washing the combined organic phases with H₂0, drying (MgS0₄) and filtration provided a yellow oily crude that was purified by flash- chromatography (flash-collector: Biotage; Si0₂; eluent: DCM) to afford the title compound. mp=85-87 °C. IR (neat) : 3313, 1774, 1305, 1142 cm^"1. ^:H NMR (500 MHz, CDCI₃) δ: 7.29-7.16, 4.96, 4.43, 4.30-4.21, 3.15, 2.76-2.70, 2.66, 2.26-2.18, 1.94-1.88, 1.79. ¹³C NMR (125 MHz, CDCI₃) δ: 174.50, 141.35, 128.43, 128.38, 126.01, 65.58, 54.25, 52.136, 35.30, 31.22, 29.81, 23.19.

Example 11 Λ/-(5-Phenylpentane-l-sulfonyl)-L-homosehne lactone 12g

A suspension of preparation 11 (90 mg, 0.39 mmol) in SOCI₂ (286 μL, 3.94 mmol) under argon with a catalytic amount of DMF (3 μL, 0.039 mmol) was heated close to reflux while stirring for 3¹/₂ hrs to yield an oil after the solvent was removed. It was dissolved in DCM (3 mL) and transferred drop-wise via syringe to preparation 1 (65 mg, 0.35 mmol) dissolved by NEt₃ (114 μL, 0.82 mmol) in DCM (6 mL). The addition was made at 0°C and under argon and took V hour. After 4 hrs of stirring the reaction mixture was allowed to warm to ambient temperature and then left overnight. Quenching (H₂0) the reaction followed by extraction (3x30 mL EtOAc), washing of the combined organic phases with H₂0, drying (MgS0 ) and filtration provided a yellow oily crude that was purified by preparative HPLC after removal of solvent in vacuum to provide the title compound. mp=41-43 °C; IR (neat) :3253, 1778, 1315, 1141 cm^"1. ^l NMR (500 MHz, CDCI₃) δ: 7.30-7.16, 4.97, 4.44, 4.32, 4.28-4.22, 3.17, 2.77-2.71, 2.64, 2.31-2.23, 1.93-1.87, 1.90 1.68, 1.48. ¹³C NMR (125 MHz, CDCI₃) δ: 174.61, 142.04, 128.36, 128.32, 125.79, 65.60, 54.34, 52.12, 35.49, 31.14, 30.77, 27.75, 23.43.

Example 12

Λ/-(3-Benzyloxypropane-l-sulfonyl --L-homoserine lactone 12h

A suspension of preparation 12 (41 mg, 0.16 mmol) in SOCI₂ (120 μL, 1.65 mmol) under argon with a catalytic amount of DMF (1 μL, 0.016 mmol) was heated close to reflux while stirring for 3Vι hrs to yield a yellowish oil after the solvent was removed. It was dissolved in DCM (1 mL) and transferred drop-wise via syringe to preparation 1 (65 mg, 0.35 mmol) dissolved by NEt₃ (114 μL, 0.82 mmol) in DCM (2 mL). The addition was made at 0°C and under argon and took Vi hour. After 4 hrs of stirring the reaction mixture was allowed to warm to ambient temperature and then left overnight. Quenching (H₂0) the reaction followed by extraction (3x30 mL EtOAc), washing of the combined organic phases with H₂0, drying (MgS0₄) and filtration provided a yellow oily crude product that was purified by preparative HPLC after removal of solvent in vacuum to yield the title compound. ^:H NMR (500 MHz, CDCI₃) δ: 7.36-7.24, 5.17, 4.49, 4.35, 4.28, 4.21-4.16, 3.68-3.60, 3.40-3.28, 2.68-2.63, 2.26-2.02. ¹³C NMR (125 MHz, CDCI₃) δ: 174.59, 137.85, 128.48, 127.82, 127.71, 73.03, 68.09, 65.60, 52.15, 51.97, 31.05, 24.40.

Example 13

ΛH6.6-Diphenyl-hexane-l-sulfonyl --L-homoserine lactone 12i

While stirring a suspension of preparation 13 (46 mg, 0.14 mmol) in SOCI₂ (0.1 mL, 1.4 mmol) at RT, a catalytic amount of DMF (1 μL, 0.014 mmol) was added. Gas was evolving, as the solid disappeared to form another solid. Heating close to reflux for 2 hrs. Remaining thionyl chloride was removed in reduced pressure (vacuum-pump) overnight leaving a clear, brown oil. It was dissolved in DCM (1 mL) and transferred drop-wise via syringe to preparation 1 (25.5 mg, 0.14 mmol) dissolved by NEt₃ (41 μL, 29 mmol) in DCM (3 mL). The addition was made at 0°C and under argon. After 2 hrs of stirring the reaction was quenched by adding water (20 mL). Extraction with EtOAc (3χ30 mL), washing the combined organic phases with H₂0, drying (MgS0₄) and filtration provided a crude product, which was purified by column chromatography to afford the title compound. mp=80-82 °C; IR (neat) = 3364, 1783, 1314, 1262, 1098, 1025 cm^"1. ^XH NMR (500 MHz, CDCI₃) δ: 7.29-7.16, 4.8, 4.43, 4.31-4.21, 3.88, 3.12, 2.76-2.71, 2.28- 2.19, 2.06, 1.87-1.79, 1.48, 1.31. ¹³C NMR (125 MHz, CDCI₃) δ: 174.48, 144.95, 128.44, 127.80, 126.12, 65.58, 54.29, 52.13, 51.27, 35.29, 31.27, 28.15, 27.49, 23.43.

Example 14 Λ/-f6,6-Dimethyl-heptane-l-sulfonyl --L-homoserine lactone 12j While stirring a suspension of preparation 14 (16 mg, 0.067 mmol) in SOCI₂ (50 μL, 0.67 mmol) at RT, cat. DMF (~1 μL) was added. Gas was evolving, as the solid disappeared to form another solid. Heating close to reflux for 3 hrs. Remaining thionyl chloride was removed in reduced pressure (vacuum-pump). The remaining colourless oil was dissolved in DCM (1.5 mL), which over a period of Vi hour was inserted drop-wise via syringe to preparation 1 (12 mg, 0.067 mmol) dissolved by NEt₃ (41 μL, 29 mmol) in DCM (3 mL). The addition was made at 0°C and under argon. After 2 hrs of stirring the reaction mixture was allowed to warm to ambient temperature and then left overnight. The solvent was removed at reduced pressure and dissolved in EtOAc (30 mL). Washing (2x20 mL H₂0), drying (MgS0₄) and filtration provided the title compound after removal of solvent in vacuum. mp=81-83 °C; IR (neat) = 3274, 1757, 1330, 1138 cm^"1 . W NMR (500 MHz, CDCI₃) δ: 4.71, 4.46, 4.35-4.24, 3.18, 2.81-2.76, 2.31-2.22, 1.92-1.85, 1.42, 1.33-1.26, 1.19-1.16, 0.89. ¹³C NMR ( 125 MHz, CDCI₃) δ: 174.43, 665.61, 54.43, 52.17, 43.83, 31.42, 30.27, 29.36, 29.15, 24.09, 23.63.

Example 15

Alternative procedure for synthesizing sulfonyl homoserine lactones

Compounds of formula I may also be synthesized using 1-hydroxybenzotriazol-l-yl- sulfonate as a starting reagent. In the following, Sx indicates an alkyl chain of x carbons, eg. S5-OBt represents the HOBt ester of pentanesulfonic acid.

Synthesis of 1-hydroxybenzotriazol-l-yl sulfonates (HOBt esters, Sx-OBt)

A more efficient and facile method for the synthesis of activated sulfonyl esters of 1- hydroxybenzotriazol has been developed as conventional activation of sodium salts of sulfonic acids by refluxing thionyl chloride followed by reaction with HOBt and a tertiary amine gave low yields (11-50% for S5-S14).

The commercial source of HOBt is in the form of a monohydrate which needs to be removed prior to use in reactions. A suitable round bottomed flask was charged with commercial 1-hydroxybenzotriazol hydrate (HOBt; Fluka 54802; 4.688 g), which was dried at 80°C under oil pump vacuum for a minimum of 5h. Weight after drying was 4.099 g or a loss of 0.589 g (12,6%) which corresponds to a monohydrate. Caution: HOBt is potentially explosive and should not be heated above 100°C.

Reaction of the sulfonic acid sodium salt as a suspension in DCM with a slight excess of oxalyl chloride in the presence of at catalytic amount of DMF smoothly gave the corresponding sulfonyl chlorides in situ. These were again reacted directly with anhydrous HOBt in the presence of an excess of K₂C0₃ in DCM. Isolated yields for a 5 mmol scale are in the range of 63-87% in excellent purity as seen below. These reaction conditions allows for a series of activated esters to be synthesized within one working day from starting material to final and isolated product.

Where the sulfonyl chlorides are commercially available, e.g. S2-4, these are added directly to the stirring suspension of HOBt and K₂C0₃. A typical procedure is outlined below for S3-OBt. Method A: Preparation from sulfonyl chloride (S3-OBt)

Scheme I: Conversion of propanesulfonyl chloride to 1-hydroxybenzotriazol propanesulfonate. a: Anhydr. HOBt, K₂C0₃, DCM, 0°C, lh.

A 25 mL round bottomed flask was charged with anhydrous HOBt (270 mg, 2.00 mmol) and K₂C0₃ (oven dried; 830 mg, 6.00 mmol) and dry DCM ( MS; 5 mL) was added. The suspension was cooled on an ice bath while propanesulfonyl chloride (Aldrich

404403; 225 μl, 2.00 mmol) was added using a Hamilton syringe. After stirring for lh, TLC (DCM) showed one spot R_f 0.55-0.64 and insignificant baseline. The reaction mixture was filtered through a syringe filter (0.45 μm) and washed with more DCM. Concentration of combined filtrate gave 0.489 g (quant.). Purity determined by RP-HPLC and identity by HRMS. HPLC (215 nm) >99%. UV_max (PDA) 255, 286 nm. HRMS (electrospray, positive mode): Calcd. for C₉Hι₂N₃0₃S⁺ (M+H) m/z 242.0594, found 242.0616 (48%); calcd. for CιιHι₅N₄0₃S⁺ (M+CH₃CN+H⁺) m/z 283.0859, found 283.0861 (100%).

Method B: Preparation from sodium salts (S7-OBt)

Scheme II: Conversion of heptanesulfonic acid sodium salt to 1-hydroxybenzotriazol heptanesulfonate. a: (COCI)₂, DMF (cat), DCM, rt., lh. b: Anhydr. HOBt, K₂C0₃, DCM, rt., lh.

An oven dried Radley Carousel reaction tube was charged with heptanesulfonic acid sodium salt (Aldrich 22,155-4; 5.00 mmol, 1,011 g) and the vessel vented three times with Ar. The sulfonic acid salt was suspended in dry DCM (8 mL) and to the stirred suspension was added oxalyl chloride (Aldrich O8801; 5.25 mmol, 460 μL) followed by dry DMF (over 4A^" MS, 20 μL). Effervescence ceased after approx. lh, but stirring can be continued over night if convenient.

Analysis by TLC of the crude reaction mixture gave significant smearing on the plate due to hydrolysis of sulfonyl chloride during elution. Instead, a few drops of the reaction mixture was diluted into a suspension of dry K₂C0₃ (approx. 20 mg) in dry MeOH (0.5 mL). Elution of the formed methyl sulfonate gave more consistent results. The absence of polar components indicated completion of activation.

The solution of crude sulfonyl chloride with suspended salts was transferred by syringe to a stirring suspension of anhydrous HOBt (5.00 mmol, 676 mg) and dry K₂C0₃ (dried at 110°C; 10.0 mmol, 1.38 g) in dry DCM (4 mL) in another oven dried Radley Carousel reaction tube. After stirring for lh, the mixture was transferred to a short column of silica gel (approx. height 40 mm, diameter of 30 mm) and eluted with dry DCM. Concentration of appropriate fractions gave OBt-ester as colorless oil (1.249 g; 84%, two steps). Crystallization was effected from hexane upon cooling. HPLC (215 nm) >99%. UV_max (PDA) 255, 286 nm. HRMS (electrospray, positive mode) : Calcd. for Cι₃H₂₀N₃O₃S⁺ (M+H) m/z 298.1220, found 298.1236 (71%); calcd. for C₁₅H₂₃N₄0₃S⁺ (M+CH₃CN+H⁺) m/z 339.1485, found 339.1510 (100%). mp. 46-47°C (uncorrected.). ^:H NMR (300 MHz, CDCI₃) δ 8.06 (IH, ddd, J = 0.8 and 8.7 Hz), 7.71 (IH, ddd, J = 1.0 and 8.4 Hz), 7.63 (IH, ddd, J = 0.8, 6.8, and 8.2 Hz), 7.47 (IH, ddd, J = 1.0, 6.8, and 8.3 Hz), 3.71 (2H, t, J = 7.6 Hz), 2.20-2.08 (2H, m), 1.62-1.49 (2H, m), 1.46-1.28 (6H, m), 0.90 (3H, t, J = 6.4 Hz). Structure confirmed by gCOSY. ¹³C NMR (75 MHz, CDCI₃) δ 143.4, 129.9, 129.1, 125.8, 120.6, 109.6, 51.9, 31.6, 28.8, 28.2, 23.6, 22.7, 14.3.

Yields, HPLC analysis, and HRMS data for all chain lengths (S2-12, and S14) are presented in table I.

Table 1: Yields and analytical data from synthesis of OBt-esters (S2-12 + 14)

¹ Done by method A. ² Done by method B. ^a DCM as eluent. M+H⁺ (+1.0073) M + MeCN+H⁺ (+42.0338). ^d EtOAc-hexane (1: 1) as eluent.

Activated OBt-esters are stored and used in couplings as a 0.5 M solution in dry r-BuOH, which again help to simplify the coupling reactions. When frozen (-20°C), these activated esters are stable even under prolonged storage. Thus, sulfonates of 1- hydroxybenzotriazol can be synthesized in high yields from different sources. Furthermore, they are potent sulfonylating agent and are more readily handled and stored than the corresponding sulfonyl chlorides.

Following the preparation of these starting materials, compounds of the invention may be prepared by Method 1 or Method 2 outlined below.

Method 1: General procedure for coupling between a HSL and a sulfonyl chloride:

The HSL salt (0.300 mmol) was dissolved in DCM (1-2 mL) and TEA (2.2 equiv) and the mixture was cooled to 5 °C by means of an ice bath. The sulfonyl chloride (1.1 equiv) was added and the reaction mixture was left with stirring at 5 °C for 30 min. The mixture was then evaporated to dryness in vacuum, dissolved in DCM to be purified on the Horizon chromatograph using the solvents EtOAc and hexane. The relevant fractions were combined. Purity was measured by HPLC (215 nm) and the composition was confirmed by HRMS. Method 2: General procedure for coupling between a HSL and an OBt-ester:

The HSL salt (0.300 mmol) was dissolved in t-BuOH (1-2 mL) and TEA (2.2 equiv) and a 0.5M solution of OBt-ester in t-BuOH (1.0 equiv) was added. The reaction mixture was left with stirring for 16 h at 30-35 °C. The mixture was then evaporated to dryness in vacuum, dissolved in DCM to be purified on the Horizon chromatograph using the solvents EtOAc and hexane. The relevant fractions were combined. Purity was measured by HPLC (215 nm) and the composition was confirmed by HRMS.

Tables with structures, yields, purity, R_f (eluent) and MS results:

(1:2). M+H (+1.0073) M+Na (+22.9892) M+K (+38.9632) M+CH₃CN+Na (+64.0158)

Sn-D-HSL:

(1:2). M+H ( + 1.0073) M+Na (+22.9892) M+K (+38.9632) M+CH₃CN+Na (+64.0158)

Sn-DL-S-HSL:

301.0650 301.0659 (100%)

¹ Done by method 1. ² Done by method 2. ^a EtOAc and hexane (1 : 1). ^b EtOAc and hexane (1 :2). ° M+H⁺ ( + 1.0073) ^d M + Na⁺ (+22.9892) ^e M+K⁺ (+38.9632) ^f M+CH₃CN+Na⁺ (+64.0158)

Sn-L-S-HSL:

Sn-D-S-HSL:

332.0753 ^e 332.0790 (10%) 357.1278 ^f 357.1292 (100%)

¹ Done by method 1. Done by method 2. ^a EtOAc and hexane (1: 1). ^b EtOAc and hexane (1:2). ° M+H⁺ (+1.0073) ^d M+Na⁺ (+22.9892) ^e M+K⁺ (+38.9632) ^f M+CH₃CN + Na⁺ (+64.0158)

Example 16

Synthesis of thiophene derivatives of sulfonyl homoserine lactones

Thiophene derivatives of sulfonyl homoserine lactone were prepared as shown in the reaction scheme shown below using Method 1 as described in Example 15.

(1:2). M+H (+1.0073) M+Na (+22.9892) M+K (+38.9632) M+CH₃CN+Na (+64.0158)

Example 17

Synthesis of furan derivatives of sulfonyl homoserine lactone

Furan derivatives of sulfonyl homoserine lactone were prepared according to the reaction scheme shown below.

Reduction of 5-formyl-2-furansulfonic acid sodium salt to 10a :

The salt (ca. 20 mmol, available from Aldrich 18,381-4) was dissolved in water (10 mL) and Raney Ni (0.4 equiv as a slurry in water) was added. The mixture was placed in a tall cylindrical flask with a magnetic stirring bar, which was fitted in to the hydrogenation apparatus. Hydrogen was let in to a pressure of approx. 70 bars and the temperature was raised to approx. 100°C. After 24 h, the heating was discontinued and after another 3 h the apparatus was disassembled. The nickel was removed by filtration and the filtrate was evaporated in vacuo. Toluene was added and the evaporation was repeated to remove residual the water from the product. Yield : 5.37g (99%), Purity >99%. H NMR (300 MHz, D₂0) 4.69 (IH, d), 4.80 (IH, d, J=0.2 Hz), 6.55 (IH, dd, .7=0.5 Hz and 3.6 Hz), 6.90 (IH, dd, .7=0.4 Hz and 3.5 Hz); ¹³C NMR (75 MHz, D₂0) δ 56.0, 109.2, 112.8, 151.1, 156.1.

Activation of 5-formyl-2-furansulfonic acid sodium salt to 10b and 10a to 10c: Representative activation of furansulfonic acids: A flask was charged with 5-formyl-2- furansulfonic acid sodium salt (595 mg, 3.00 mmol; Aldrich 18,381-4), which was suspended in POCI₃ (1.25 mL) and cooled by means of an ice bath. To the stirring suspension was added PCI₅ (3.1 g, 15.0 mmol) over a period of 15 min while still cooling. The ice bath was removed and the reaction mixture was allowed to warm to rt. and then stirred at ambient temperature for 3h. TLC (EtOAc-hexane) showed the disappearance of polar components R_f 0 and the formation of a new spot Rf 0.53-0.62 (both visualized by KMn0₄ reagent). The crude reaction mixture was transferred directly to a column of silica gel and eluted with an EtOAc-hexane gradient. Appropriate fractions were combined and concentrated to an oil (580 mg, 77%). Purity > 98% (HPLC 215 nm). UV max (PDA) 216 and 258. ^XH NMR (300 MHz, CDCI₃) δ 7.28 (IH, d, J = 3.6 Hz), 6.84 (IH, d, J = 3.6 Hz), 6.71 (IH, s). ¹³C NMR (75 MHz, CDCI₃) δ 156.0, 150.3, 119.5, 111.2, 61.1. Coupling between the activated furans and L-HSL to lOd and lOe: The coupling was performed by Method 1 as described in Example 15.

lOd : TLC in Ethyl acetate- hexane (1 : 1) R_f=0.62-0.67; The product was concentrated to a colourless oil, mass 14.2 mg (30%). Purity > 99% (HPLC 215 nm). UV max (PDA) 242 nm; MS (MS_caι_c) : 279 (278.9968); 244 (M-CI); 179 (M-HSL); ^:H NMR (CDCI₃) δ 2.24- 2.39 (1H₄, m), 2.74-2.83 (1H₄, m), 4.16-4.31 (2H₅, m), 4.47 (1H₃, dd, -7=8.7 Hz), 4.59 (2Hi₀, s), 6.52 (1H₈, d, .7=3.5 Hz), 7.05 (1H7, d, .7=3.5 Hz); ¹³C NMR (CDCI₃) δ 31.5, 36.6, 52.3, 66.3, 110.9, 118.0, 148.1, 155.0, 173.9

lOe:

TLC in Ethyl acetate-hexane (1 : 1) R_f=0.23-0.34; The product was concentrated to a colourless oil, mass 341 mg (46%) Purity > 99% (HPLC 215 nm). UV max (PDA) 242 nm; MS (MS_ca,_c) : 313 (312.958); 278 (M-CI); 213 (M-HSL); HRMS (ES+) : M-CI requires 277.9890, found 277.9897 (43%) ;^:H NMR (CDCI₃) δ 2.24-2.39 (1H₄, m), 2.76-2.85 (1H₄, m), 4.20-4.31 (2H₅, m), 4.44-4.51 (1H₃, dd, J=9.3Hz), 5.42 (1NH, s), 6.68 (lHι₀, s), 6.75 (1H_8/ d, J=3.7Hz), 7.07 (1H₇, d, J=3.7Hz); ¹³C NMR (CDCI₃) δ 31.4, 52.4, 61.6, 66.2, 110.6, 117.4, 149.0, 154.3.

/V-(5-formylfuran-2-sulfonyl .-L-homoserine lactone (lOf. :

The Λ/-(5-dichloromethylfuran-2-sulfonyl)-homoserine lactone (82.4 mg; lOe) was weighed off in to a reaction flask and dissolved in a solution of water (250 μL) and formic acid (750 μL, 98-100%). The mixture was left with stirring for 36 h while the conversion was followed by HPLC. The hydrolyzed product was then purified directly by flash chromatography on Horizon using EtOAc-hexane as solvents, R_f= 0.08-0.15 in EtOAc- hexane (1 : 1). Appropriate fractions were concentrated to yield the title compound as colorless oil (56.6 mg; 83%). HPLC: Purity > 99% (215 nm), UV max (PDA) 275 nm. MS (MScaic) : 260.0267 (H⁺ 260.0229), 282.0054 (Na⁺ 282.0049), 323.0296 (MeCN+Na⁺ 323.0314). ^XH NMR (CDCI₃) δ 2.25-2.40 (IH, m), 2.68-2.78 (IH, m), 4.20-4.28 (IH, ddd, J= 6.1 and 9.7 and 11.6 Hz), 4.29-4.36 (IH, dd, J= 8.8 and 11.8 Hz), 4.40-4.47 (IH, ddd, .7= 1.0 and 9.1 Hz), 6.88 (NH), 7.15 (IH, d, J= 3.6 Hz), 7.25 (IH, d, J= 3.4 Hz), 9.74 (IH, s) ¹³C NMR (CDCI₃) δ 30.9, 52.4, 66.0, 116.8, 119.8, 153.2, 153.9, 173.9, 178.4

Λ/-(5-hydroxymethylfuran-2-sulfonyl)-L-homoserine lactone (lOα . :

Λ/-(5-formylfuran-2-sulfonyl)-L-homoserine lactone (34.6 mg, lOf) was weighed off in a reaction flask and dissolved in 1 mL THF. To the solution was slowly added a suspension of NaBH₄ (1.0 mg) in 0.5 mL THF. The solution was kept at room temperature by means of a water bath. The conversion was followed by HPLC, and after completion of the reaction, the mixture was removed from the bath and left for 10 min while stirring. Aqueous hydrochloric acid (10 μL, 4M HCl) was added and the mixture was concentrated to be purified by flash chromatography in a mixture of EtOAc and hexane. TLC R_f 0.28- 0.33 (EtOAc). HPLC: purity 97% (215 nm), UV max (PDA) 236 nm. MS (MS_ca._c) : 279.0632 (NH₄ ⁺ 279.0651), 284.0167 (Na⁺ 284.0205), 325.0415 (MeCN+Na⁺ 325.0470). ^XH NMR (D₂0) δ 1.90-2.04 (IH, m), 2.22-2.34 (IH, m), 4.03-4.15 (IH, m) 4.39-4.22 (2H, m), 4.44 (2H, s), 6.38 (IH, d J=3.3Hz), 7.00 (IH, d, J=3.8Hz); ¹³C NMR (D₂0) δ 29.1, 52.2, 55.8, 67.1, 109.8, 118.6, 146.2, 159.1, 177.6.

Deoxofluor

Λ/-(5-Difluoromethylfuran-2-sulfonyl .-L-homoserine lactone (lOh) :

An oven dried reaction tube was charged with /V-(5-formylfuran-2-sulfonyl)-L- homoserine lactone (lOf, 19.4 mg, 0.075 mmol), which was dissolved in dry DCM (1 mL; 4A MS). Approx. 30 mg Deoxyfluor (Fluka 95463) was dissolved in dry DCM (0.3 mL; 4A MS) and added to the stirring solution. To generate HF in situ, abs. EtOH (2 μl) was added. The reaction mixture was stoppered and stirred over night at rt. TLC (EtOAc - hexane 1: 1): Reaction mixture showed no presence of aldehyde (R_f 0.06-0.14; develops with KMn0₄ and dinitrophenylhydrazine (DNPH)) and a new spot R_f 0.16-0.27 (KMn0₄, no coloration with DNPH reagents). The reaction mixture was purified on Horizon (EtOAc- hexane gradient) and appropriate fractions were concentrated to yield the title compound as colorless oil. HPLC: purity 97% (215 nm), UV max 229 nm (PDA); HRMS: m/z required for CuHi₂F₂N₂Na0₅S⁺ (M+Na+CH₃CN) 345.0326, found 345.0341 (100%). ^l NMR (CDCI₃) δ 7.12 (IH, br. ά, J = 3.9 Hz), 6.79-6.76 (IH, m), 6.65 (IH, t, J_HF = 54 Hz), 5.46 (IH, br. s, NH), 4.47 (IH, ddd, J = 9.0 and 1 Hz), 4.31-4.18 (2H, m), 2.84- 2.74 (IH, m), 2.40-2.23 (IH, m); ¹⁹F NMR (CDCI₃) δ -117.1 (dd, J = 54 and approx. 5 Hz).

Example 18

Synthesis of 4- and 5-substituted homoserine lactones

Protected (Λ/-carbonyloxybenzyl, Λ/-Cbz) homoserine lactones carrying 4-hydroxy groups were synthesized according to a literature procedure (J. A. Olsen et al. (2002) Bioorg. Med. Chem. Lett. 12, 325-328).

Λ/-Cbz protected compounds were deprotected using Pd black (prepared according to B. S. Furniss, A. J. Hannaford, P. W. G. Smith, and A. R. Tatchell, Vogel's Textbook of Practical Organic Chemistry, 5^th ed., Prentice Hall, 1989, p. 453) and a hydrogen donor in a suitable solvent. Typical procedure: An oven dried Radley reaction tube was charged with protected starting material (0.100 mmol) and Pd black (106 mg, 0.100 mmol). Dry DMF (4A MS, 800 μl) was added followed by 1,4-cyclohexadiene (Fluka 28910; 94 μL, 1.00 mmol) and the mixture was stirred magnetically for 30-60 min. Analysis of the reaction mixture by TLC (EtOAc or EtOAc-hexane) indicated completion when no apolar components was observed together with a strong coloration of the baseline with ninhydrin reagent. To this reaction mixture, without further purification, was added the sulfonylating agent (sulfonyl chloride or OBt-ester as a 0.5 M solution) and a suitable base (Et₃N, DIEA). Work-up procedure was performed as described previously.

Protected (Λ/-t-Butyloxycarbonyl, Λ/-Boc) homoserine lactones carrying 4- or 5-methyl substituents were synthesized according to a literature procedure (B. D. Dangel, J. A. Johnson, and D. Sames -7. Am. Chem. Soc 2001, 123, 8149-8150). Λ/-Boc protected compounds were deprotected using ethanolic hydrochloric acid. Typical procedure: An oven dried Radley reaction tube was charged with protected starting material (0.100 mmol), which was dissolved in HCl in EtOH (Fluka 17934, 1.25 M, 0.5 mL). After stirring over night (18h), the reaction mixture was concentrated to a colorless solid. After drying under oil pump vacuum for 3-4h, the formed hydrochloride salt was used in coupling reactions as described elsewhere.

/V-Butanesulfonyl-4-c/s-hvdroxy-L-homoserine lactone (Ila)

Synthesized as described above from the N-Cbz protected derivative. R_f 0.15-0.21 (EtOAc-hexane 1 : 1). Isolated yield after purification by chromatography 22%. HPLC purity 85% (215 nm). HRMS (ethanolic solution) : M+Na+CH₃CN requires 301.0828, found 300.9773 (46%); M+Na+CH₃CN+EtOH requires 347.1247, found 347.0289 (100%).

/V-Hexanesulfonyl-4-c-s-hydroxy-L-homoserine lactone (lib)

Synthesized as described above from the N-Cbz protected derivative. R_f 0.14-0.22 (EtOAc-hexane 1 : 1). Isolated yield after purification by chromatography 36%. HPLC purity 94% (215 nm). HRMS: M+K requires 304.0616, found 304.0656 (20%); M+Na+CH₃CN requires 329.1141, found 329.1166 (100%)

Λ/-Octanesulfonyl-4-c/s-hvdroxy-L-homosehne lactone (lie)

Synthesized as described above from the N-Cbz protected derivative. R_f 0.17-0.26 (EtOAc-hexane 1 : 1). Isolated yield after purification by chromatography 29%. HPLC purity 93% (215 nm). HRMS (ethanolic solution) : M+H requires 294.1370, found 294,1408 (6%); M+NH₄ requires 311.1635, found 311.1667 (15%); M+Na+CH₃CN requires 357.1454, found 357.1526 (90%); M+Na+CH₃CN+EtOH requires 403.1873, found 403.1899 (100%). Λ.-Decanesulfonyl-4-c-s-hydroxy-L-homoserine lactone (lid)

Synthesized as described above from the N-Cbz protected derivative. R_f 0.21-0.27 (EtOAc-hexane 1: 1). Isolated yield after purification by chromatography 29%. HPLC purity 95% (215 nm). HRMS: M+H requires 322.1683, found 322.1863 (5%); M+Na+CH₃CN requires 385.1767, found 385.1797 (100%).

Λ/-Butanesulfonyl-4--raπs-hydroxy-L-homoserine lactone (He)

Synthesized as described above from the N-Cbz protected derivative. R_f 0.13-0.21 (EtOAc-hexane 1: 1). Isolated yield after purification by chromatography 13%. HPLC purity 97% (215 nm). HRMS (solution in EtOH): M + Na+CH₃CN+EtOH requires 347.1247, found 347.1278 (100%).

-V-Hexanesulfonyl-4-fraπs-hydroxy-L-homoserine lactone (llf)

Synthesized as described above from the N-Cbz protected derivative. R_f 0.16-0.22 (EtOAc-hexane 1 : 1). Isolated yield after purification by chromatography 22%. HPLC purity 85% (215 nm). HRMS (solution in EtOH): M+Na+CH₃CN+EtOH requires 375.1560, found 375.1574 (100%).

-V-Butanesulfonyl-4-^rans-methyl-L-homoserine lactone (llq)

Synthesized as described above from the Λ/-Boc protected derivative. R_f 0.34-0.36 (EtOAc-hexane 1 : 1). Isolated yield after purification by chromatography 26%. HPLC purity 82% (215 nm). HRMS: M+H requires 236.0951, found 236.0946 (9%); M+Na requires 258.0770, found 258.0780 (18%); M+Na+CH₃CN requires 299.1035, found 299.1027 (100%) -V-Butanesulfonyl-4-c-s-methyl-L-homoserine lactone (lib)

Synthesized as described above from the N-Boc protected derivative. R_f 0,33-0.37 (EtOAc-hexane 1 : 1). Isolated yield after purification by chromatography 7%. HPLC purity 85% (215 nm). HRMS: M+H requires 236.0951, found 236.0939 (9%); M+Na+CH₃CN requires 299.1035, found 299.1049 (100%)

Λ/-Butanesulfonyl-5-methyl-L-homoserine lactone (Hi)

Synthesized as described above from the Λ/-Boc protected derivative. R_f 0.30-0.36 (EtOAc-hexane 1 : 1). Isolated yield after purification by chromatography 50%. HPLC purity 72% (215 nm). HRMS: M+H requires 236.0951, found 236.0934 (11%); M+Na requires 258.0770, found 258.0769 (20%); M+Na+CH₃CN requires 299.1035, found 299.1033 (100%)

Example 19

QSI activity of compounds according to formula I

E. coli, into which the LuxR-QS-monitor was incorporated, was inoculated from an over night culture in fresh growth medium at a density of approximately OD450= 1, incubated at 37 °C for approximately 30 min. Aliquots (200 μl) of this culture were distributed to the wells of microtiter dishes in which 25, 50 and 100 nM Λ/-(3-oxohexanoyl)-L- homoserine lactone (OHHL), and Λ/-heptanesulfonyl-L-homoserine lactone at 0, 1, 2, 3, 6, 13, 25 and 50 μM was already present. After two hours of incubation at 37 °C the relative fluorescence units (RFU) of each sample were captured with in Wallac Victor², 1420 Multilabel Counter using a 485 nm excitation filter and a 535 nm emission filter. Table 2 gives the RFU values for each microtiter well. Table 2: RFU for N-heptanesulfonyl-L-homoserine lactone

For each OHHL concentration, the concentration of Λ/-heptanesulfonyl-L-homoserine lactone which lowers the RFU values to 40% at the level without Λ/-heptanesulfonyl-L- homoserine lactone is calculated. These values are plotted against the OHHL concentration, and slope of the straight line best fitting the three point (II₄₀) were calculated

Similar experiments were conducted for other compounds of formula I, and the results are shown in Table 3 below

Table 3: Examples of II₄₀ values

The data show that compounds according to formula I are potent quorum sensing inhibitors.

Example 20

DNA microarray analysis

The P. aeruginosa PAOl was obtained from the Pseudomonas Genetic Stock Center (www.pseudomonas.med.ecu.edu, strain PAO0001). This PAOl isolate has served as DNA source for the Pseudomonas Genome Project (www.pseudomonas.com) and, subsequently, as template for design of the P. aeruginosa GeneChip (Affymetrix, Inc, Santa Clara, Calif.). The strain was grown at 37 °C in ABt medium containing 0.5% Casamino acids. 100 ml medium was preheated for 10 minutes and inoculated with one ml of an overnight culture. The culture was grown to OD₆₀₀«0.3 and diluted 15: 100 in preheated medium. This culture was grown to OD_600*0.5 where it was spilt into three cultures. One culture was treated with 30 μM Λ/-(5-dichloromethyl-2-furansulfonyl)-L- homoserine lactone (referred to as compound lOe above), another was an untreated control (referred to as φ). The concentrations used were chosen as to show maximum inhibition of the lasB-gfp fusion harbored by PAOl and at the same time show no effect on growth. Growth was monitored to OD₆o₀«2.0 where samples for RNA isolation were taken, immediately transferred to 2 volumes of RNAIater (Ambion Inc., Austin, Texas) and stored at -80°C.

RNA purification and further processing for DNA microarray analysis was performed according to the guidelines by manufacturer of the GeneChip^® P. aeruginosa Genome Array (Affymetrix Inc., Santa Clara, Calif.). Microarray data analysis was performed using Affymetrix Microarray Suite 5.0 and Data Mining Tool 3.0 software. Average microarray hybridization signal intensity was scaled to 2,500. For data analysis, the minimum and maximum signal thresholds were set to 200 and 100,000, respectively.

Table 4: Results for RNA isolation and cDNA synthesis. Synthesis of cDNA was done from 12 μg RNA from each sample. Note: Measurements are performed on 3:77 dilutions

3 μg cDNA from each sample was fragmented with 1.2 U DNase for 10 minutes. The fragmented cDNA was labeled with biotin for 1 h, after which agarose gel (1% in TBE) electrophoresis was performed on samples incubated for 5 minutes with and without neutravidin. DNA arrays was hybridized with 54 μl labeled cDNA for 17 hours at 50 °C. After hybridization the arrays were stained and scanned according to the Affymetrix protocol. All data are scaled to a global average of 500.

Data analysis

In order to identify a correlation between known quorum sensing regulated genes and genes affected by compound lOe, a consensus data set was made for OD₆₀₀«2.0. It was based on a previous data set obtained with four untreated samples of PAOl at OD₆oo»2.0. A hybridization signal for a given gene must be present in at least two of the four arrays in order to be recorded as present. The consensus signal is calculated as the average of the values from the arrays that has the given gene marked present. An algorithm was used to remove "outliers" before the average signal intensity was calculated. Comparing the recent QSI untreated (φ) control to the consensus only yields 20 genes regulated 3- fold or more and 3 genes 5-fold or more (data not shown). This indicates that our recent QSI untreated array is close to the "true" or consensus array. Genes that are down regulated upon compound lOe treatment are then identified by comparing with the consensus untreated data set (at OD₆₀₀∞2.0). Genes down regulated 5-fold or more are thought to be significantly affected by the treatments.

Quorum sensing regulated genes were identified according to the procedure described by Hentzer et al., EMBO J. , 2003, in press, as follows. Hybridization data sets for a P. aeruginosa lasl rhll double mutant grown with and without addition of the signals BHL and OdDHL were acquired in the following way. A culture of a lasl rhll mutant was grown to an OD600 of 0.3. The culture was split in three and added : i) no AHLs, ii) 2 μM OdDHL, and iii) 2 μM OdDHL and 5 μM BHL. Samples from RNA preparation were retrieved at the OD₆₀₀-values of 1.3, 1.6, 2.0, and 2.7. RNA purification and further processing for microarray analysis was performed according to the guidelines by manufacturer of the GeneChip® P. aeruginosa Genome Array (Affymetrix Inc., Santa Clara, Calif.). Microarray data analysis was performed using Affymetrix Microarray Suite 5.0 and Data Mining Tool 3.0 software. Average microarray hybridisation signal intensity was scaled to 2,500. For data analysis, the minimum and maximum signal thresholds were set to 200 and 100,000, respectively. The data represent results of at least two independent experiments. A Mann-Whitney test was used to identify genes showing differential expression (p < 0.05). In this communication, we have only shown genes more than five-fold repressed or induced and with absolute difference in hybridization signal of >600. In our experimental settings, these criteria corresponded to a p-value < 0.03. Genes, which were transcribed five fold or more upon signal addition were defined as regulated by quorum sensing.

From the results it appeared that compound lOe down regulated expression of 57 of the 178 (32.6%) QS regulated genes many of which encode major QS regulated virulence factors. Expression of the following QS regulated genes were found to be more than five fold reduced, PA0059, PA0122, PA0355, PA0567, PA0852, PA1131, PA1323, PA1324,

PA1784, PA1871, PA1901, PA1902, PA1903, PA1904, PA1905, PA2030, PA2031, PA2068, PA2069, PA2300, PA2414, PA2433, PA2564, PA2566, PA2570, PA2747, PA2939, PA3273, PA3274, PA3361, PA3370, PA3478, PA3479, PA3691, PA3692, PA3724, PA3890, PA4078, PA4078, PA4129, PA4130, PA4131, PA4133, PA4134, PA4141, PA4142, PA4143, PA4175, PA4209, PA4210, PA4211, PA4217, PA4738, PA4739, PA5059, PA5481, PA5482. If genes in the 2-5 fold range were included, expression of 91 QS regulated genes (51.1%) was down regulated by compound lOe treatment.

The compound lOe seems to be fairly specific for QS. On a global scale, about 2-3% of the genome is targeted indicating that the compound is not a general (growth) inhibitor. A significantly higher proportion (10-12 fold) of the QS genes are targeted indicating that QS regulated genes are the target for this compound. The specificity - the fraction of QS targets vs. total targets - is about 1 in 3, also indicating QS as target for compound lOe.

Example 21 Pulmonary mouse model

Healthy CBA/J mouse strains at the age of 11 weeks (average body weight 30 g) were used in animal studies. The mouse total body volume was estimated to be 20 ml, which for the calculation of concentrations equals approximately 20 gram. The bacterial strain used in this animal study is an Escherichia coli harboring a dual monitor plasmid. The dual monitor plasmid directs expression of red fluorescent protein (Rfp) via a constitutive promoter and green fluorescent protein (Gfp) via a quorum sensing regulated promoter. Hence, the presence of Rfp indicates that the cells are viable whereas expression from the QS regulated promoter is only stimulated in the presence of the QS signal molecule Λ/-(3-oxo-hexanoyl)-L-homoserine lactone (OHHL) when present in concentrations above a certain threshold. Immobilization of E. coli (1 x 10⁹ CFU/ml) in seaweed alginate beads and the surgical introduction of bacteria into mouse lungs (40 μl injected per lung) was performed as previously described (Wu er a/., Microbiology, 146, 2481 2000). The mice were given QS signals and QS inhibitors by intravenous injection. QS signal molecules and QS inhibitors were prepared as stock solutions in 96% ethanol, which were diluted 83-fold in 0.9% NaCl prior to injection. Intravenous injection in the tail vein was applied to ensure that drugs were transported directly to the lung before passing the liver. Preparation of lung tissue samples, subsequent SCLM (Scanning Confocal Laser Microscopy) examination and determination of lung bacteriology were performed as described elsewhere (Wu et al. , Microbiology, 146, 2481 2000). This model was used to evaluate the efficacy of the present compounds in vivo. In the absence of the QS signal all E. coli cells were exclusively red fluorescent (no green fluorescence developed) serving as a negative control. In the presence of the QS signal OHHL (~43 ng/g body weight), but absence of a QS inhibitory signal all E. coli cells were both red and green fluorescent, serving as a positive control. However, intravenous co- administration of the QS inhibitor compound lOe (~10 and 20 μg/g body weight) with OHHL (~43 ng/g body weight) caused repression of the Gfp signal. QS inhibition by ~20 μg/g body weight of compound lOe was reversed by increasing dosages of OHHL (~86, 172 and 344 ng/g body weight). This shows that compound lOe can be transported by the blood circulation to the lungs, penetrate the lung tissues, enter the bacteria, and in turn repress QS-controlled gene expression without affecting bacterial growth.

Claims

1. A compound of general formula I

wherein RI is alkyl, alkenyl, alkynyl or heteroaryl, each of which being optionally substituted with one or more alkyl, hydroxy, halogen, haloalkyl, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonylalkyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino, alkylcarbonylamino, aryl or heteroaryl, each aryl or heteroaryl being optionally substituted with one or more hydroxy, halogen, amino, cyano, carboxy, haloalkyl, alkylcarbonyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino or alkylcarbonylamino; or a radical of the formula -(R^a-Z-R^b-)_n-H, wherein each R^a independently represents a Ci-is straight or branched, saturated or unsaturated hydrocarbon diradical optionally substituted by hydroxy, halogen, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonylalkyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino, alkylcarbonylamino, aryl or heteroaryl, and wherein each R independently represents a bond or a Cι-₁₀ straight, branched and/or cyclic hydrocarbon diradical, optionally substituted by hydroxy, halogen, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino, alkylcarbonylamino or phenyl; n being 1, 2 or 3; Z represents O, C(O), C(0)-0, NH or an aromatic or non-aromatic heterocyclic diradical;

R2 is hydrogen, alkyl, alkenyl or alkynyl all of which are optionally substituted with one or more hydroxy, halogen, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonylalkyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, alkoxycarbonylalkyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino, alkylcarbonylamino, aryl or heteroaryl, wherein said aryl or heteroaryl may optionally be substituted by on one more hydroxy, halogen, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, alkoxycarbonylalkyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino or alkylcarbonylamino; or a radical of the formula -(R^a-Z-R^b)_n-H; X is O or S;

Y is 0, S or NR9, wherin R9 represents hydrogen, alkyl or phenyl; each R3, R4, R5, R6, R7 and R8 independently represent hydrogen, hydroxy, halogen, alkyl, alkenyl, alkynyl, amino, cyano, carboxy, alkylcarbonyl, alkylcarbonylalkyl, alkylcarbonyloxy, alkoxy, alkoxycarbonyl, alkoxycarbonylalkyl, aminocarbonyl, aminocarbonylalkyl, thio, alkylthio, aminosulfonyl, alkylsulfonylamino, alkylcarbonylamino or phenyl; or wherein R4 and R5 and/or R6 and R7 together with the two ring carbon atoms to which they are attached form a 5 or 6 membered carbocyclic or heterocyclic ring; one of R3, R4, R5, R6, R7 and R8 is absent to provide a vacant valence for binding to the nitrogen; with the proviso that if RI is methyl then Y is not S; and pharmaceutically acceptable salts or degradation products thereof.

A compound according to claim 1 which has the structure of formula la

A compound according to claim 1 which has the structure of formula lb

A compound according to claim 1 which has the structure of formula lc

5. A compound according to any of claims 1-4 wherein RI is alkyl.

6. A compound according to any of claims 1-4 wherein RI is C_.-ι₀alkyl.

7. A compound according to any of claims 1-4 wherein RI is alkyl substituted by one or more phenyl.

8. A compound according to any of claims 1-4, wherein RI is selected from the group consisting of 2-oxopropyl, 3-benzoyloxypropyl, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, 3-phenylpropyl, 4-phenylbutyl, 5-phenylpentyl, 6,6-diphenylhexyl and 6,6-dimethylheptyl, 5-chloromethyl-2-furyl and 5-dichloromethyl-2-furyl.

9. A compound according to any of claims 1-4, wherein Z is 0 or C(O).

10. A compound according to any of claims 1-4 wherein R3 is hydrogen.

11. A compound according to any of claims 1-4 wherein X and Y are both 0.

12. A compound according to any of claims 1-4 wherein Y is NH.

13. A compound according to any of claims 1-4 wherein X is S.

14. A compound according to any of claims 1-4, wherein R4 and R7 are both hydrogen, and wherein R5 and R8 are independently selected from the group consisting of alkyl, aminocarbonyl and R^a-0-R^b-H.

15. A compound according to claim 1 selected from the group consisting of -V-methansulfonyl-L-homoserine lactone;

-V-ethanesulfonyl-L-homoserine lactone;

Λ/-propanesulfonyl-L-homoserine lactone;

Λ/-butanesulfonyl-L-homoserine lactone; Λ/-pentanesulfonyl-L-homoserine lactone;

Λ/-hexanesulfonyl-L-homoserine lactone;

/V-heptanesulfonyl-L-homoserine lactone;

Λ/-2-oxo-propanesulfonyl-L-homoserine lactone;

Λ/-(3-phenylpropane-l-sulfonyl)-L-homoserine lactone; Λ/-(4-phenylbutane-l-sulfonyl)-L-homoserine lactone;

Λ/-(5-phenylpentane-l-sulfonyl)-L-homoserine lactone; /-(3-benzyloxypropane-l-sulfonyl)-L-homoserine lactone;

Λ/-(6,6-diphenylhexane-l-sulfonyl)-L-homoserine lactone;

Λ/-(6,6-dimethylheptane-l-sulfonyl)-L-homoserine lactone; Λ/-(5-chloromethyl-2-furansulfonyl)-L-homoserine lactone; and

Λ/-(5-dichloromethyl-2-furansulfonyl)-L-homoserine lactone.

16. The use of a compound according to any of claims 1-15 in therapy.

17. A pharmaceutical preparation comprising a compound according to any of claims 1-15, optionally together with another therapeutically active compound, and optionally together with a pharmaceutically acceptable excipient.

18. A preparation according to claim 17 in unit dosage form.

19. A preparation according to claim 17, wherein said other therapeutically active compound is selected from the list containing penicillins, selexcid, cephalosporins, tetracyclines, rifamycins, gentamycin, clindamycin, fluoroquinolones, monobactamers, carbapenemes, macrolides, polymyxins, aminoglycosides, tobramycin, sulfonamides, fusidines, vancomycines, oxazolidinones, metronidazoles and corticosteroids, hydrocortisone, triamcinolone and betamethasone.

20. The use of a compound according to any of claims 1-15 in the preparation of a medicament for the treatment or prevention infections.

21. The use according to claim 20, wherein said infection is bacterial

22. The use according to claim 20, wherein said infection is a Pseudomonas aeruginosa infection.

23. The use according to claim 20, wherein said infection is a Pseudomonas aeruginosa infection in the lungs of cystic fibrosis patients, on burns or on implants.

24. A method of treating infections comprising administering to a patient in need thereof an effective amount of a compound according to any of claims 1-15, optionally in combination with, either concomitantly or sequentially, another therapeutically active compound.

25. A method according to claim 24 wherein said infection is bacterial.

26. A method according to claim 24, wherein said infection a Pseudomonas aeruginosa infection.

27. A method according to claim 24, wherein said infection is a Pseudomonas aeruginosa in the lung of cystic fibrosis patients, on burns or on implants.

28. A method according to any of claims 25-27, wherein said other therapeutically active compound is selected from the list consisting of penicillins, selexcid, cephalosporins, tetracyclines, rifamycins, gentamycin, clindamycin, fluoroquinolones, monobactames, carbapenemes, macrolides polymyxins, aminoglycosides, tobramycin, sulfonamides, fusidines, vancomycines, oxazolidinones, metronidazoles and corticosteroids, hydrocortisone, triamcinolone and betamethasone.

29. An endoprothesises impregnated with a compound according to any of claims 1-15.

30. A method of treatment that prevents cystic fibrosis patients from being chronically infected with Pseudomonas aeruginosa in the lungs, the method comprising administering to a patient an effective amount of a compound according to any of claims 1-15.

31. A method of controlling bacterial growth, the method comprising contacting said bacteria with an effective amount of a compound according to any of claims 1-15, optionally in combination with a bacteriostatic or bacteriocidal compound.

32. The method according to claim 31, wherein said bacteriostatic or bacteriocidal compound is selected from amongst the group consisting of penicillins, selexcid, cephalosporins, tetracyclines, rifamycins, gentamycin, clindamycin, fluoroquinolones, monobactames, carbapenemes, macrolides polymyxins, aminoglycosides, tobramycin, sulfonamides, fusidines, vancomycines, oxazolidinones, metronidazoles and corticosteroids, hydrocortisone, triamcinolone and betamethasone.