WO1997034881A1

WO1997034881A1 - Bis-heterocyclic derivatives

Info

Publication number: WO1997034881A1
Application number: PCT/DK1997/000112
Authority: WO
Inventors: Kurt Vesterager Gothelf
Original assignee: Aarhus Universitet
Current assignee: Aarhus Universitet
Priority date: 1996-03-15
Filing date: 1997-03-14
Publication date: 1997-09-25
Anticipated expiration: 1998-09-15
Also published as: AU2151897A

Abstract

Compounds of general formula (I) wherein R?1, R2, R3, R4, R5, R6, R7, and R8¿ each independently are: hydrogen; halogen; nitro; nitroso; cyano; a group -CO-Z-R10, -CS-Z-R10, -SO2-Z-R?10?, -C(NH)-NR?10R11, -CO-R10, -SO-R10, -SO¿2-R10, -Z-CO-R10, -Z-CO-Z-R10, -Z-CS-R10 or -Z-SO¿2?-R?10, -O-R10, -S-R10 or -NR10R11¿, wherein each Z independently is -O-, -S- or -N(R11)-; optionally substituted, linear or branched C¿1-10?alkyl, C2-10alkenyl, C4-10alkadienyl, C6-10alkatrienyl, C2-10alkynyl, C3-8cycloalkyl, C3-8cycloalkenyl, C4-8cycloalkadienyl, C6-8cycloalkatrienyl or C3-8cycloalkyl-C1-4alkyl; or R?3 and R7¿, and/or R?4 and R8¿ together form a bond; or R?1 and R2¿, and/or R?5 and R6¿ together form a bivalent group -(CH¿2?)n- wherein n is an integer from 3 to 5, or a bivalent group -Z-(C(R?15)¿2)m-Z- wherein m is an integer from 1 to 3; X?1 and X2¿ each independently is O, S, or N(R12); and Y?1 and Y2¿ each independently is N or C(R13); with the proviso that when X?1-Y1 and X2-Y2¿ are both O-N, and R?3 and R7, and R4 and R8¿, each together form a bond, then at least one of R?1, R2, R5, and R6¿ is different from hydrogen, or that R?1 and R6¿ are both different from nitro, methyl and unsubstituted phenyl; and physiologically acceptable salts thereof. Such compounds have anti-cancer properties.

Description

BIS-HETEROCYCLIC DERIVATIVES

FIELD OF THE INVENTION

The present invention relates to bis-heterocyclic derivatives having anti-cancer properties.

Sϋ__MA Y OF THE INVENTION

The invention relates to compounds of the general formula I

wherein

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, and R⁸ each independently are: hydrogen; halogen; nitro; nitroso; cyano; a group -CO-Z-R¹⁰, -CS-Z-R¹⁰ or -SO--Z-R¹⁰ wherein Z is -0- , -S- or -NtR¹¹) - ; a group -C(NH) -NR¹⁰R^1:L; a group -CO-R¹⁰, -SO-R¹⁰ or -S0₂-R¹⁰; a group -Z-CO-R¹⁰, -Z-CO-Z-R¹⁰, -Z-CS-R¹⁰ or -Z-S0₂-R¹⁰ wherein each Z independently is as defined above; a group -0-R¹⁰ or -S-R¹⁰; a group -NR¹⁰R^1:L; where groups R¹⁰ and R¹¹ each independently are hy¬ drogen or is optionally substituted C₁_₈alkyl, aryl, aryl-C-_L._gal yl where an alkyl group or moiety may be interrupted by -0- , -S- or -N(R¹⁴)- wherein R¹⁴ is hydrogen, C-^galkyl or aryl, and where the optional

SUBSTITUTE8HEET(RULE26) substituent (s) are selected from halogen, nitro, amidine, cyano, mercapto, C_1-8alkylthio, arylthio, hydroxy, C-.galkoxy, aryloxy, amino, C^_^._galkylamino, arylamino, diC-^galkylamino, diarylamino, formyl, C₁_₈alkylcarbonyl, arylcarbonyl, C-^_galkoxycarbonyl, aryloxycarbonyl, C-^galkylcarbonyloxy, aryloxycarbo- nyloxy, or two neighbouring substituents together form a bivalent group -Z- (C (R¹⁵) ₂)_m-Z- wherein each Z independently is as defined above, R¹⁵ is hydrogen or C₁_₂alkyl, and m is an integer from 1 to 3; optionally substituted, linear or branched ^_.-^alky!, optionally substituted, linear or branched C₂_₁₀alkenyl or C₄_₁₀alkadienyl or C₆_₁₀alkatrienyl, optionally substi¬ tuted, linear or branched C₂.₁₀alkynyl, or optionally substituted C₃.₈cycloalkyl, C₃.₈cycloalkenyl, C₄_₈cycloal- kadienyl, C₆_₈cycloalkatrienyl or C₃.₈cycloalkyl-C₁_₄alkyl where the optional substituen (s) are selected from halogen, nitro, cyano, -CO-Z-R¹⁰, -S0₂-Z-R¹⁰, -CO-R¹⁰, -SO-R¹⁰, -S0₂-R¹⁰, -Z-CO-R¹⁰, -Z-S0₂-R¹⁰, -O-R¹⁰, -S-R¹⁰, and -NR¹⁰R^ι:L wherein Z, R¹⁰ and R¹¹ are as defined above; aryl or aryl - C₁._i -alkyl where the aryl moiety may be substituted from 1 to 6 substituents selected from C₁_₄- alkyl, halogen, nitro, nitroso, cyano, a group -CO-Z-R¹⁰, -CO-Z-R¹⁰, -S0--Z-R¹⁰, -CO-R¹⁰, -SO-R¹⁰, -S0₂-R¹⁰, -Z-CO-R¹⁰, -Z-S0₂-R¹⁰, -O-R¹⁰, -S-R¹⁰, or -NR¹⁰R^1:L wherein Z, R¹⁰ and R¹¹ are as defined above; or R³ and R⁷, and/or R⁴ and R⁸ together forms a bond; or R¹ and R , and/or R⁵ and R⁶ together forms a bivalent group - (CH₂)_n- wherein n is an integer from 3 to 5, or a bivalent group -Z- (C<R¹⁵) ₂)_m-Z- wherein Z, R¹⁵ and m is as defined above;

X¹ and X² each independently is 0, S, or N(R¹²) , wherein R¹² is a group as defined for R¹⁰; and

Y¹ and Y² each independently is N or C(R¹³) wherein R¹³ is a group as defined for R¹⁰ above; with the proviso that when X¹-Y¹ and X²-Y² are both O-N, and R³ and R⁷ together forms a bond, and R⁴ and R⁸ together forms a bond, then at least one of R¹, R², R⁵, and R⁶ is different from hydro- gen, or

R¹ and R⁶ are both different from nitro, methyl and unsubsti- tuted phenyl; and physiologically acceptable salts thereof.

DETAILED DESCRIPTION OF THE INVENTION

In the general formula I, the wavy lines connecting R⁷ and R⁸ to the respective ring system indicate that each substituent in question may be in any of the two possible conformations.

In the present context, the terms "C-_L.-_LQalkyl" and "C₁_₈alkyl" used to define a group or part of a group designates an alkyl group having from 1 to 10 carbon atoms and from 1 to 8 carbon atoms, respectively, and examples of such groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec.butyl, tert.butyl, pentyl , hexyl, heptyl, octyl, nonyl and decyl . In a preferred embodiment, the alkyl group has 1-6 carbon atoms, in particular 1-4 carbon atoms. An alkoxy group designates a corresponding alkyl group bound via an oxygen atom.

Similarly, the term "C₂_₁₀alkenyl" used to define a group or part of a group designates an alkenyl group having from 1 to 10 carbon atoms, and examples of such groups are ethenyl, 1- and 2-propenyl, 1-, 2- and 3-butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl and decenyl . In a preferred embo¬ diment, the alkenyl group has 1-6 carbon atoms, in particular 1-4 carbon atoms.

Likewise, the term "C₄.₁₀alkadienyl" used to define a group or part of a group designates a diunsaturated group having from 1 to 10 carbon atoms, and examples of such groups are butadienyl, pentadienyl, hexadienyl, heptadienyl, nonadienyl, and decadienyl. Furthermore, the term "C₅_₁₀alkatrienyl" used to define a group or part of a group designates a triunsaturated group having from 1 to 10 carbon atoms, and examples of such groups are hexatrienyl, heptatrienyl, nonatπenyl, and decatrienyl.

The term "C₃._θcycloalkyl" used to define a group or part of a group designates a cyclic alkyl radical of from 3 to 8 carbon atoms, and examples of such groups are cyclopropyl, cyclobu- tyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Likewise, the term "C₃_₈cycloalkenyl" designates a cyclic, monounsaturated radical of from 3 to 8 carbon atoms, and examples of such groups are cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, and cyclooctenyl. The term "C₄_₈cycloalkadιenyl" designates a cyclic, diunsatu- rated radical having from 4 to 8 carbon atoms, and examples of such groups are cyclopentadienyl, cyclohexadienyl, cyclo- heptadienyl, and cyclooctadienyl . The term "C₆_₈cycloalkatri- enyl" designates a cyclic, triunsaturated radical of from 6 to 8 carbon atoms, and examples of such groups are cyclohep- tatrienyl and cyclooctatrienyl .

The term "halogen" comprises fluoro, chloro, bromo and iodo.

The term "aryl" used to define a group or part of a group designates an aromatic group which may be mono-, bi- or tricyclic, and be carbocyclic or heterocyclic, as well as partially or completely hydrogenated forms of such cyclic groups. Examples of a carbocyclic aryl group are phenyl, naphthyl, indenyl, and anthracyl . A heterocyclic aryl group may be a monocyclic, 5- or 6-meιribered ring containing from 1 to 4, preferably 1 or 2 heteroatoms selected from nitrogen, oxygen and sulfur. Examples of such groups are pyrrolyl, furanyl, thienyl, oxazolyl, thiazolyl, imidazolyl, isoxazo- lyl, isothiazolyl, pyrazolyl, pyridmyl, pyπmidinyl, triazo- lyl, tetrazolyl, oxazmyl, thiazinyl, triazmyl, dihydropyri- dinyl, piperidmyl and piperidino, dihydropyranyl, tetrahyd- ropyranyl . A heterocyclic aryl group may also be a bicyclic ring system having 8-10 members and containing from 1 or 2 heteroatoms selected from nitrogen, oxygen and sulfur. Examples of such groups are indolyl, coumaryl, purinyl, benzofuranyl, quinolinyl, isoquinolinyl, dihydroquinolinyl, dihydroisoquinolinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, quinazolinyl.

If two neighbouring substituents together form a bivalent group -Z- (C(R¹⁵) ₂)_m-Z- , a preferred example of such a bivalent substituent is -0- (C (R¹⁵) ₂)_m-0- , in particular -0- (CH₂)_m-0- , especially -0-CH₂-0- and -0-C (CH₃) ₂-0- .

The term "physiologically acceptable salts" means salts formed with non-toxic, physiologically acceptable acids or bases of the types well known in the art of pharmaceuticals. Examples of physiologically acceptable acid addition salts are salts with inorganic acids such as hydrochloric, hydrobromic, sulfuric, sulfamic, sulfonic, sulfanilic, nitric, phosphoric acid and the like; as well as salts with organic acids such as acetic, propionic, maleic, fumaric, benzoic, succinic, tartaric, citric, glycolic, malic, lactic, pamoic, ascorbic, stearic, phenylacetic, glutamic, salicylic acid and the like. Examples of salt with bases are salts formed with alkaline or earth alkaline metal hydroxides such as salts formed with sodium, potassium, calcium or magnesium hydroxide.

Depending on the substituents present in the general formula I, the compounds of the invention may contain one or more asymmetric carbon atoms, whereby the compound may exist in two or more isomeric forms. In such cases, the present inven¬ tion as defined by the general formula I is intended to comprise each and every individual stereoisomer such as an enantiomer, as well as mixtures thereof, including racemic mixtures.

Each of the ring moieties X¹-Y¹ and X²-Y² may be any of those possible in the formula. Examples of such ring moieties are 0-N, S-N, N(R¹²)-N, 0-C(R¹³) , S-C(R¹³), and N(R¹²) -C(R¹³) where R¹² and R¹³ are as defined above. Consequently, depen¬ dent also on whether R³ and R⁷ and/or R⁵ and R⁸ together form a bond, each of the two rings in the formula I may indepen¬ dently be an isoxazole, isoxazoline, isothiazole, isothiazo- line, pyrazole, pyrazoline, furan, dihydrofuran, thiophene, dihydrothiophene, pyrrol, or pyrroline ring.

In a preferred embodiment, the compounds of the invention are such in which the moieties X¹-Y¹ and X²-Y² are the same, in particular where they are both O-N, i.e. that each ring independently is either an isoxazoline ring or, especially, if R³ and R⁷ together form a bond, or R⁵ and R⁸ together form a bond, an isoxazole ring.

It is contemplated that preferred compounds are those in which R³ and R⁷ together form a bond, and R⁵ and R⁸ together form a bond, i.e. each ring is an isoxazole ring, R² and R⁵ are both hydrogen, and R¹ and R⁶ independently are unsubsti- tuted or substituted aryl groups, in particular unsubstituted phenyl or phenyl substituted with the groups defined above, in particular substituted with one to four groups selected from hydroxy, halogen, amino, alkylamino, dialkylamino, mercapto, alkylthio, nitro, sulfonyl, C₁_₈alkoxy, C-^_galkyl- or arylcarbonyloxy, C-^_galkyl- or arylcarbonylamino, C-^gal- kyl- or arylsulfonylamino, or two neighbouring substituents together form a bivalent group -Z- (C(R¹⁵) ₂)_m-Z- , wherein Z and R¹⁵ are as defined above.

Examples of compounds of the invention are: 5,5' -bis- (3- (4' ' -hydroxyphenyl) -isoxazole) , 5,5' -bis- (3- (2' ' -hydroxyphenyl) -isoxazole) , 5,5'-bis- (3- (3' ' -hydroxyphenyl) -isoxazole) , 5,5'-bis-(3-(2'' ,4'' -dihydroxyphenyl) -isoxazole) , 5,5' -bis- (3- (3' ' , 4' ' -dihydroxyphenyl) -isoxazole) , 5,5' -bis- (3- (3' ' ,5' ' -dihydroxyphenyl) -isoxazole) , 5,5' -bis- (3- (2' ' , 5' ' -dihydroxyphenyl) -isoxazole) , 5,5' -bis- (3- (2' ' ,3' ' ,4' ' - rihydroxyphenyl) -isoxazole) , 5,5' -bis- (3-(3' ',4'',5' ' -trihydroxyphenyl) -isoxazole) , 5,5 ' ' -methoxyphenyl) -isoxazole) ,

5,5 ' ' -methoxyphenyl) -isoxazole) ,

5,5 ' ' ,4' ' -dimethoxyphenyl) -isoxazole) ,

5,5 ' ' 5' ' -dimethoxyphenyl) -isoxazole) ,

5,5 ' ' , 3' ' , 4' '-trimethoxyphenyl) -isoxazole) ,

5,5 ' ' , 4' ' , 5' '-trimethoxyphenyl) -isoxazole) ,

5,5 ' ' -acetoxyphenyl) -isoxazole) ,

5,5 ' ' , 4 ' ' -diacetoxyphenyl) -isoxazole) ,

5,5 ' ' , 5 ' ' -diacetoxyphenyl) -isoxazole) ,

5,5 ' ' ,5' ' -diacetoxyphenyl) -isoxazole) ,

5,5 ' ' , 3 ' ' , 4' ' -triacetoxyphenyl) -isoxazole) ,

5,5 3 ' ' , 4 ' ' , 5' ' -triacetoxyphenyl) -isoxazole) ,

5,5 ' ' -benzyloxyphenyl) -isoxazole) ,

5,5 3' ' -benzyloxyphenyl) -isoxazole) ,

5,5 2' 4' -dibenzyloxyphenyl) -isoxazole) ,

5,5 3' 4' -dibenzyloxyphenyl) -isoxazole) ,

5,5 3' 5' -dibenzyloxyphenyl) -isoxazole) ,

5,5 2' 5' -dibenzyloxyphenyl) -isoxazole) ,

5,5 2' 3 ,4' ' -tribenzyloxyphenyl) -isoxazole)

5,5 3' ' 4 , 5 ' ' -tribenzyloxyphenyl) -isoxazole)

5,5 3' ' -hydroxy-4' ' -methoxyphenyl) -isoxazole) ,

5,5 4' ' -hydroxy-3' ' -methoxyphenyl) -isoxazole) ,

5,5 3' ' ,4' ' -methylendioxyphenyl) -isoxazole) ,

5,5 3' ', 4' '- (2, 2-propylendioxy)phenyl) - isoxazole)

5,5 4' ' -nitrophenyl) -isoxazole) ,

5,5 4' ' -aminophenyl) -isoxazole) ,

5,5 4' ' -acetaminophenyl) -isoxazole) ,

5,5 4' ' -chlorophenyl) -isoxazole) ,

5,5 4' ' -bromophenyl) -isoxazole) ,

5,5 4' ' -iodophenyl) -isoxazole) ,

5.5 4' ' -sulfonylphenyl) -isoxazole) , 5,5' -bis- (3- (4' ' -amidinophenyl) -isoxazole) , and 5,5' -bis- (3- (4' ' -carboxyphenyl) -isoxazole) .

As indicated above, compounds of the invention have anti- cancer properties in that they have demonstrated growth- reducing properties in in vitro assays against several cancer cell lines. Examples of interesting cancer types are prostate cancer, colon cancer, CNS-cancer, non-small cell lung cancer, breast cancer, renal cancer, leukaemia, ovarian cancer, testicular cancer, lymphatic cancer, pancreatic cancer, melanoma, oesophageal cancer, stomach cancer, and intestinal cancer.

Consequently, the present invention preferably relates to those of the compounds of the general formula I which, when tested against a mammalian cancer cell line in accordance with the standard procedure of the National Cancer Institute in vi tro Anticancer Drug Discovery Screen, results in a Percentage Growth (PG) , as defined herein, below 90, prefe¬ rably 80, in particular 70, especially 60, such as 50.

This screening procedure is described in detail in Boyd, M.R. & Paull, K.D.: "Some practical considerations an applications of the National Cancer Institute in vitro Anticancer Drug Discovery Screen", Drug Development Research 1995, 34 , pp 91- 109 and references cited therein.

Similarly, the present invention preferably relates to those of the compounds of the general formula I which, when tested against a mammalian cancer cell line in accordance with the above indicated standard procedure exhibits a Response Para¬ meter GI50 value, as defined herein, at a concentration of at the most 10^"4 with respect to at least one mammalian cancer cell line. The GI50 value may be viewed as a growth inhibi¬ tory level of effect.

Also, the present invention preferably relates to those of the compounds of the general formula I which, when tested against a mammalian cancer cell line in accordance with the above indicated standard procedure does not exhibit a LC50 value, as defined herein, at a concentration of below 10^"4 M. The LC50 value is the lethal concentration, "net cell kil- ling" or cytotoxicity parameter.

The compounds of the invention may be prepared by methods known per se in the art. Thus, the compounds in which and R³ and R⁷ together form a bond, and R⁴ and R⁸ together form a bond may be prepared by any known reaction for the cross- coupling between two aromatic five-membered rings. Examples of such reactions are the Stille cross-coupling reaction (Stille, J.K., Angew. Chem. 1986, 1986 , p 504) and the Suzuki reaction (Miyaura, N. ; Ishiyama. T.; Sasaki, H. ; Ihikawa, M. ; Suzuki, A., J.Am . Chem. Soc . 1989, 111 , p 314) .

Thus, a compound of the general formula II

in which R¹, R², X¹, and Y¹ are as defined above, and L¹ is Cl, Br, I or -0-S0₂-CF₃, is reacted with a compound of the general formula III

in which R⁵, R⁶, X², and Y² are as defined above, and L² is -SnBu₃ (where Bu designates n-butyl) or -B(OH)₂ in the pre¬ sence of a catalytic amount of a palladium catalyst such as Pd(PPh₃)₄ or Pd(AsPh₃)₄ (where Ph designates phenyl) . The reaction is usually carried out under an inert gas in an organic aprotic, polar solvent such as dioxan or tetrahydro- furan, at a temperature between room temperature and the boiling point of the solvent, for a period of from 1 to 48 hours.

When the two ring systems and their substituents in the compound to be prepared are identical, the synthesis may also be carried out by reacting a compound of the formula II alone or a compound of the formula III alone under the above condi¬ tions with the exception that a Pd(II) compound such as PdCl₂ or PdCl₂(PPh₃)₂ is used, preferably in an amount of at least 0.5 mole equivalent calculated on the compound II or III.

Furthermore, compounds in which X¹-Y¹ and X²-Y² are both 0-N, and R², R³, R⁴ and R⁵ are all hydrogen, may be prepared by reacting a compound of the general formula IV

R¹-CH=N-0H IV

with a halogenating agent, preferably a chlorinating agent such as N-chlorosuccinimide, followed by treatment with a base to give the corresponding nitrile oxide, followed imme¬ diately by treatment with one mole equivalent of a compound of the formula V

H₂C=C(R⁷) -C(R⁸)=CH₂ V

After a period of time in the order of 0.5 to 2 hours, the resulting 5-vinyl-isoxazoline intermediate is treated with a nitrile oxide generated from a compound of the general for- mula VI

R⁶-CH=N-OH VI in the same manner as described above for formula IV.

The nitrile oxide preparation step(s) may be carried out in a aprotic polar solvent such as chloroform, dichloromethane or ethyl acetate, at temperatures between 0 and 80°C. After stirring for a period, the subsequent 1, 3-elimination of HC1 to give the nitrile oxide is normally carried out at tempera¬ tures from -20 to +50°C with a mild base such as KHC0₃, dilute triethylamine, dilute pyridine or the like.

The compounds wherein X¹-Y¹ and X²-Y² are both 0-N, and R³ and R⁷ together form a bond, and R⁴ and R⁸ together form a bond, may also be prepared in a method similar to the one described above involving the compounds IV, V, and VI. The difference lies in the fact that following the reaction with the nitrile oxide generated from the compound VI, an elimi- nation reaction is carried out, and this is made possible by using a compound of the general formula V in which R⁷ and R⁸ are both groups capable of undergoing a 1, 2-elimination reaction with a hydrogen atom on the neighbouring carbon atom. Examples of such groups are Br, Cl, I, trialkylsilyloxy such as trimethylsilyloxy, or morpholino, and the elimination is carried out by treatment with acid or base, dependent on which type of group is used as R⁷ and R⁸, as it will be familiar to the person skilled in the art.

The starting compounds of the formulas II, III, IV, V, and VI are known compounds or may be prepared according to pro¬ cedures known in the art (see i.a. (a) Kondo, Y. ; Uchiyama, D.; Sakamoto, T.; Yamanaka, H. Tetrahedron Lett. 1989, 30, p 4249, and (b) Hansson, L.; Carlson, R. Acta Chem. Scand . 1989, 43 , p 304) .

The invention further relates to a pharmaceutical composition comprising one or more of the compounds of the general for¬ mula I'

wherein R^: R-% R^J, R*, R=, R^e R⁷, and R⁸ each independently are: hydrogen; halogen; nitro; nitroso; cyano; a group -CO-Z-R¹⁰ -CS-Z-R¹⁰ or -SO -Z-R¹⁰ wherein Z i_

-0- , -S- or -N(R^ι:L) - ; a group -C (NH) -NR¹⁰R^1:L; a group -CO-R¹⁰, -SO-R¹⁰ or -SO ^■R 10. a group -Z-CO-R¹⁰, -Z-CO-Z-R¹⁰, -Z-CS-R 10 or Z-S0₂-R 10 wherein each Z independently is as defined above; a group -O-R¹⁰ or -S-R¹⁰; a group -NR¹⁰R^ι:L; where groups R¹⁰ and R¹¹ each independently are hy¬ drogen or is optionally substituted C₁.₈alkyl, aryl, aryl-C-_L._galkyl where an alkyl group or moiety may be interrupted by -0-, -S- or -N(R¹⁴)- wherein R¹⁴ is hydrogen, C_j.galkyl or aryl, and where the optional substituent (s) are selected from halogen, nitro, amidine, cyano, mercapto, C-__₈alkylthio, arylthio, hydroxy, C-^_galkoxy, aryloxy, amino, C-^_galkylamino, arylamino, diC₁.₈alkylamino, diarylamino, formyl, C-_L.galkylcarbonyl, arylcarbonyl, C-^_galkoxycarbonyl , aryloxycarbonyl, C₁.₈alkylcarbonyloxy, aryloxycarbo- nyloxy, or two neighbouring substituents together form a bivalent group -Z- (C(R 15

> > m - ^z - wherein each Z independently is as defined above, R¹⁵ is hydrogen or C_1.2alkyl, and m is an integer from 1 to 3; optionally substituted, linear or branched C₁.₁₀alkyl, optionally substituted, linear or branched C₂.₁₀alkenyl or C₄_₁₀alkadιenyl or C₆_₁₀alkatrιenyl, optionally substi¬ tuted, linear or branched C₂.₁₀alkynyl, or optionally substituted C_3.8cycloalkyl, C₃.₈cycloalkenyl, C₄_₈cycloal- kadienyl, C₆_₈cycloalkatπenyl or C₃_₈cycloalkyl-C₁_₄alkyl where the optional substituen (s) are selected from halogen, nitro, cyano, -CO-Z-R¹⁰, -S0₂-Z-R¹⁰, -CO-R¹⁰,

-SO-R¹⁰, -S0₂-R¹⁰, -Z-CO-R¹⁰, -Z-S0₂-R¹⁰, -O-R¹⁰, -S-R¹⁰, and -NR¹⁰R¹¹ wherein Z, R¹⁰ and R¹¹ are as defined above; aryl or aryl-C₁_₄-alkyl where the aryl moiety may be substituted from 1 to 6 substituents selected from C _₄ - alkyl, halogen, nitro, nitroso, cyano, a group -CO-Z-R¹⁰, -CO-Z-R¹⁰, -S0₂-Z-R¹⁰, -CO-R¹⁰, -SO-R¹⁰, -S0₂-R¹⁰, -Z-CO-R¹⁰, -Z-S0₂-R¹⁰, -O-R¹⁰, -S-R¹⁰, or -NR¹⁰R^1:L wherein Z, R¹⁰ and R¹¹ are as defined above; or R³ and R⁷, and/or R⁴ and R⁸ together forms a bond; or R¹ and R², and/or R⁵ and R⁶ together forms a bivalent group - (CH₂)_n- wherein n is an integer from 3 to 5, or a bivalent group -Z- (C (R¹⁵) ₂)_m-Z- wherein Z, R¹⁵ and m is as defined above;

X¹ and X² each independently is 0, S, or N{R¹²) , wherein R 12 is a group as defined for R¹⁰ above; and

Y¹ and Y² each independently is N or C(R¹³) wherein R¹³ is a group as defined for R¹⁰ above; m combination with a pharmaceutically acceptable carrier.

The compounds of the invention are conveniently administered to warm-blooded animals, e.g. mammals such as humans, orally, parenterally (e.g. intravenously, intramuscularly or mtrape- ritoneally) , topically, or rectally in dosage forms contai¬ ning conventional, non-toxic, pharmaceutically acceptable carriers, adjuvants and vehicles. The formulation and pre- paration of any of this spectrum of dosage forms into which the compounds of the invention can be disposed is well-known to those skilled in the art of pharmaceutical formulation. Specific information and techniques may, however, be found in the text entitled "Remington's Pharmaceutical Sciences" Sixteenth Edition, 1980.

The pharmaceutical compositions containing the compounds of the invention may be in a form suitable for oral use, e.g. as tablets, troches, lozenges, aqueous or oily suspensions, solutions, or emulsions, dispersible powders or granules, hard or soft capsules, syrups or elixirs. .The compositions for oral use include tablets which contain the active ingred¬ ient in admixture with non-toxic, pharmaceutically acceptable excipients such as inert diluents, e.g. calcium carbonate, sodium chloride, lactose, calcium phosphate, or sodium phos- phate; granulating and disintegrating agents, e.g. potato starch or alginic acid; binding agents, e.g. starch, gelatin or acacia; and lubricating agents, e.g. magnesium stearate, stearic acid or talc. The tablets may be uncoated or be coated by known techniques to delay disintegration and ab- sorption in the gastrointestinal tract to provide sustained action.

Oral formulations may also be presented as hard gelatin capsules wherein the active ingredient is mixed with an inert solid diluent such as calcium carbonate, calcium phosphate or kaolin, or as soft gelatin capsules wherein the active ingre¬ dient is mixed with water or an oil medium such as peanut or olive oil or liquid paraffin.

Aqueous suspension usually contain the active compounds in admixture with suitable excipients such as suspending agents, e.g. sodium carboxymethylcellulose, methylcellulose, hydroxy- propylmethylcellulose, sodium alginate, polyvinylpyrrolidone, gum tragacanth and gum acacia; dispersing or wetting agents which may be a naturally occurring phosphatide e.g. lecithin, a condensation product of ethylene oxide with a long-chain alcohol (e.g. heptadecaethyleneoxycetanol) , with a partial ester derived from fatty acids and a hexitol (e.g. polyethylene sorbitol monooleate) , and with a partial ester derived from fatty acids and hexitol anhydrides (e.g. polyethylene sorbitan monooleate) . The aqueous suspensions may also contain one or more preservatives such as methyl, ethyl or n-propyl p-methoxybenzoate, as well as colouring, sweetening or flavouring agents.

A composition for parenteral administration may be a sterile solution or an aqueous or oleaginous emulsion or suspension. Such compositions may be formulated according to the known art using suitable well-known dispersing or wetting agents selected among those mentioned above. The sterile injectable preparation may be a sterile injectable solution or suspen¬ sion in a parenterally acceptable diluent or solvent such as sterile, pyrogen-free water, 1, 3-butanediol, Ringer's solu¬ tion and isotonic sodium chloride solution.

The compounds of formula I may also be administered in the form of suppositories for rectal administration of the com¬ pounds. Such compositions may be prepared by mixing the compound with a suitable non-irritating excipient which is solid at normal temperature but liquid at the rectal tempera¬ ture, e.g. cocoa butter or adeps solidus polyethylene gly- cols.

In therapeutic applications, the compounds of the invention or the pharmaceutical compositions containing them are admin¬ istered to a patient in an amount sufficient to produce the desired effect, defined as a "therapeutically effective dose" . The therapeutically effective dose of a compound of the invention will vary according to, for example, the par- ticular use for which the treatment is made, the manner of administration, the health and condition of the patient, and the judgement of the prescribing physician. For example, the dose for continuous infusion will typically be in the range of about 10 μg to about 5 g per day for a 70 kg patient, preferably between about 0.1 mg and about 1 g. The invention is further illustrated by the following, non- 1imiting examples.

EXPERIMENTAL

The ^XH NMR spectra were recorded on a Varian Gemini spectro- meter at 200 MHz or 300 MHz. Chemical shifts for ¹H NMR are reported in ppm downfield from tetramethylsilane (TMS) . Mass spectra were recorded on a Varian Gemini Micro-Mass 7070F spectrometer operating at 70 eV with a direct inlet. Prepara¬ tive thin layer chrom tography (PTLC) was performed on 200x200x1,8 mm silica gel (PF₂₅₄-_.366' Merck) on glass plates. Solvents were dried using standard procedures.

EXAMPLE 1

Bis 5, 5' - (3- (4^* ' -hydroxyphenyl) isoxazole) (la), Method A:

In a 100 mL round bottom flask containing a 30 mm teflon- coated magnetic stirring bar and 50 mL of EtOAc, 4-hydroxy- benzaldehyde oxime (2,057 g, 15 mmol) was placed. After stirring for 5 min at room temperature, N-chlorosuccinimide (2,128 g, 16 mmol) was added. The mixture was stirred at room temperature for 2 h. Thereafter, bis-2, 3- (trimethylsilyloxy)- • 1, 3-butadiene (1,151 g, 5 mmol) was added. After 1 min., a solution of triethylamine (1,162 g,l6 mmol) in EtOAc (10 mL) was added over a period of 5 min. The reaction mixture was stirred for 3 h at room temperature. The mixture was filtered through a layer of celite and the solvent of the filtrate was evaporated in vacuo. The precipitate was dissolved in 10 mL of glacial acetic acid and cone. H₂S0₄ (0,5 mL) was added to the mixture. A reflux condenser was fitted to the flask and the flask was placed in an oil bath at 120°C with stirring for 2h. Water (20 mL) was added and the mixture was cooled to room temperature. The precipitate was filtered off, and washed with H₂0 (10 mL) . After drying, the residue was purified by column chromatography (Et₂0:petroleum ether, 2:1) . The product was recrystallized from acetonitrile to give compound la.

^XH NMR (Acetone d₆) δ: 6,90 (d, J=8,9 Hz, 4H) , 7,05 (s, 2H) , 7,68 (d, J=8,9 Hz, 4H) ; MS _nz=320 (M⁺) .

EXAMPLE 2

Bis-5, 5' - (3- (4' ' -hydroxyphenyl) isoxazole) (la) : Method B:

In a 5 mL round bottom flask, a 10 mm teflon coated stirring bar, dry dioxane (2 mL) and 3- (4' -hydroxyphenyl) -5- (tributyl- stannyl) -isoxazole (450 mg, 1 mmol) was placed under nitro¬ gen. PdCl₂ (88,7 mg, 0,5 mmol) was added to the solution. The flask was fitted with a reflux condenser and heated on a oil bath at 100°C. The mixture was stirred at this temperature for 24 h. The crude mixture was cooled to room temperature and filtered through a layer of celite (10 mm) . The solvent was removed by evaporation in vacuo . The residue was purified by preparative thin layer chromatography (PTLC) (Et₂0:petro- leum ether; 2:1, rf=0,4) . The solid product was recrystallized from acetonitrile to give la (30 mg, 6%) as white crystals.

¹H NMR (Acetone d₆)δ: 6,90 (d, J=8,9 Hz, 4H) , 7,05 (s, 2H) , 7,68 (d, J=8, 9 Hz, 4H) ;

EXAMPLE 3

Bis-5, 5' - (3- (4-hydroxyphenyl) -isoxazoline) (2a) :

In a 100 mL round bottom flask containing a 30 mm teflon- coated magnetic stirring bar and 50 mL of ethyl acetate, 4-hydroxybenzaldehyde oxime (2,057 g, 15 mmol) was placed. After stirring for 5 min at room temperature, N-chlorosuccin- imide (2,128 g, 16 mmol) was added and the mixture was stirred at room temperature for 1 h. The reaction flask was cooled to -15°C in a ice/NaCl bath, and the flask was sealed with a rubber septum. Liquid 1,3-butadiene (400 μL g, 5 mmol) cooled to -78°C was added through the septum via a syringe. After 1 min, a solution of triethylamine (1,162 g, 16 mmol) in EtOAc 10 mL was added over a period of 5 min. The reaction mixture was heated to room temperature and stirred for 3 h. The solvent was removed by evaporation in vacuo and the residue was dissolved in 5 mL of a mixture of 5% MeOH in CH₂C1₂- The crude product was purified by column chromato- graphy on silica gel (200 g, 5% MeOH in CH₂C1₂) . The selected fractions containing minor byproduct impurities was recrystallized in MeOH/CH₂Cl₂ to give pure 2a as a single diastereomer (430 mg, 32%) . mp=265-270°C (dec.) ^λE NMR (Acetone d₆)δ: 3,27 (dd, J= 17,33, 6,67 Hz, 2H) , 3,53 (dd, J=17,33, 9,33 Hz, 2H) , 4,79 (m, 2H) , 6,90 (d, J=9,07 Hz, 4H) , 7,68 (d, J=9,07 Hz, 4H) ; MS _rιz=324 (M⁺) .

TEST EXAMPLE

The NCI in vi tro disease-oriented primary antitumour screen used for testing compounds of the invention has been pub¬ lished in Seminars in Oncology, 1992, 19 , page 622-638. The test compound, bis-5, 5'- (3- (4'' -hydroxyphenyl) -isoxazole) , was tested on a total of 60 cell lines representing 9 diffe¬ rent types of cancer, the tests being conducted at a minimum of five concentrations at 10-fold dilutions. A 48 hours continuous drug exposure protocol was used, and a sulforho- damine B (SRB) protein assay was used to estimate cell viabi- lity or growth.

The Calculated Measurement of Effect: Percentage Growth (PG)

The measured effect of the compound on a cell line was calcu¬ lated according to one or the other of the following two expressions:

If (Mean 0D_test - Mean 0D_tzero) ≥ 0, then

PG = 100 x (Mean OD_test - Mean 0D_tzero) / (Mean 0D_ctrl - Mean

^0Dtzero> If (Mean 0D_test - Mean 0D_t__ero) < 0, then

PG = 100 (Mean ODtest Mean 0D_tzero) /Mean OD_tzero

where Mean ODtzero The average of optical density measurements of SRB-derived colour just before exposure of cells to the test compound.

Mean 0D_test The average of optical density measurements of SRB-derived colour after 48 hours of exposure of cells to the test compound. Mean OD_ctrl The average of optical density measurements of SRB-derived colour after 48 hours with no exposure of cells to the test compound.

The data obtained are shown in Table 1 and 2 below.

• _

0-

__

LoglO Concen ration

Time Mean Optical Densities Percent Growth

Parip'. /Cel 1 LI no Zero :trl -7.0 -6.0 -5.0 -4.0 -8.0 -7.0 -6.0 -5.0 -4.0 GI50 TGI LC50

9.24E-07 >1.00E-04 >1.00E-04

1.45E-06 M.00E-04 >1.00E-04

3.40E-06 >1.00E-04 >1.00E-04

1.66E-06 2.20E-05 >1.00E-04

3.52E-06 >1.00E-04 M.OOE-04 3.99E-06

6.98E-05 M.OOE-04 M .OOE-04

3.09E-05 M.OOE-04 M .OOE-04

2.59E-05 M.OOE-04 M .OOE-04

>1.00E-04 M.OOE-04 M .00E-04

>1.00E-04 M.OOE-04 M.OOE-04

>1.00E-04 M.OOE-04 M. OOE-04

M.OOE-04 M.OOE-04 M.OOE-04

7.24E-05 M.OOE-04 M.OOE-04

2.14E-05 M.00E-04 M.OOE-04

M.OOE-04 M.OOE-04 M.OOE-04

4.03E-05 M.OOE-04 M.OOE-04

3.94E-05 M.OOE-04 M.OOE-04

6.74E-07 M.OOE-04 M .OOE-04

M.OOE-04 M.OOE-04 M.OOE-04

1.13E-05 M.00E-04 M.00E-04

M. OOE-04 M. OOE-04 M.OOE-04

2.51E-05 M.OOE-04 M.OOE-04

8.35E-05 M.OOE-04 M.OOE-04

3.36E-06 2.47E-05 M.OOE-04

M. OOE-04 M.OOE-04 M.OOE-04

2.79E-05 M.OOE-04 M.OOE-04

3.71E-05 M.OOE-04 M.OOE-04

tr¹ __

o O rt H- d α> o-

Lo lO Concentration

GI50 TGI LC50

7.29E-05 M.OOE-04 M. OOE-04

4.97E-05 M. OOE-04 M. OOE-04

M. OOE-04 M. OOE-04 M.OOE-04

2.30E-05 M. OOE-04 M.00E-04

M.00E-O4 M. OOE-04 M. OOE-04

1.74E-05 M. OOE-04 M. OOE-04

1.57E-05 M.OOE-04 M. OOE-04

6.65E-05 M. OOE-04 M. OOE-04

M.OOE-04 M. OOE-04 M. OOE-04

M. OOE-04 M. OOE-04 M. OOE-04

M.OOE-04 M.00E-04 M. OOE-04

>1. OOE-04 M. OOE-04 M. OOE-04

3.31E-06 M.00E-04 M. OOE-04

6.61E-05 M. OOE-04 M. OOE-04

7.46E-07 M.00E-04 M. OOE-04

M. OOE-04 M.OOE-04 M.00E-04

6.06E-05 M.OOE-04 M. OOE-04

7.05E-06 M. OOE-04 M.OOE-04

1.72E-05 M. OOE-04 M. OOE-04

M. OOE-04 M. OOE-04 M. OOE-04

5.95E-06 M. OOE-04 M. OOE-04

. M. OOE-04 >1.00E-04

8.45E-05 M.OOE-04 M. OOE-04

LoglO Concen ration Mean Optical Densities Percent Growth

Ctrl -8.0 -7.0 -6.0 -5.0 -4.0 -8.0 -7.0 -6.0 -5.0 -4.0 GI50 TGI LCS0

CD CO

1.715 684 1.668 1.509 1.261 0.979 97 96 82 61 37 2.86E-05 M.OOE-04 M. OOE-04 1.133 048 1.015 0.970 0.918 0.912 88 83 76 69 68 M. OOE-04 M. OOE-04 M. OOE-04 0.653 621 0.595 0.582 0.458 0.459 94 88 86 61 61 M.00E-04 M.OOE-04 M. OOE-04 m 1.360 144 1.178 1.058 1.038 0.816 74 78 64 62 36 2.85E-05 M.OOE-04 M. OOE-04

CO 1.398 314 1.389 1.254 1.061 0.997 91 99 85 65 59 M. OOE-04 M.OOE-04 M. OOE-04 0.856 824 0.766 0.744 0.736 0.627 93 81 77 75 53 M. OOE-04 M.OOE-04 M. OOE-04

21 329 1.312 1.298 1.193 .074 0.801 98 97 87 76 51 M.OOE-04 M. OOE-04 M. OOE-04 3 172 1.141 1.118 1.133 .088 1.032 96 93 95 88 81 M.00E-04 M. OOE-04 M. OOE-04 996 1.020 0.881 0.591 .505 0.538 103 87 54 44 48 2.39E-06 M.OOE-04 M. OOE-04

575 1.527 1.686 1.581 .349 0.995 95 112 101 76 38 4.86E-05 M. OOE-04 M. OOE-04

790 0.761 0.750 0.736 .764 0.610 93 91 88 94 61 M.OOE-04 M. OOE-04 M.OOE-04

021 0.988 0.958 0.920 .927 0.793 95 90 85 86 65 M.00E-04 M.OOE-04 M.OOE-04

1 .769 1.753 1.706 1.618 1.483 1.387 98 93 84 70 60 M.OOE-04 M.OOE-04 M. OOE-04

1.435 1.433 1.424 1.263 0.990 0.836 100 99 81 51 34 1.08E-05 M.OOE-04 M. OOE-04

738 ,594 1.579 1.328 905 697 88 87 66 31 14 2.89E-06 M.OOE-04 M.OOE-04 673 .564 2.531 2.139 617 362 93 91 68 36 21 3.68E-06 M.OOE-04 M. OOE-04

0.982 1.010 0.958 0.962 830 533 104 97 98 81 44 6.82E-05 M. OOE-04 M.OOE-04 1.606 1.615 1.547 1.544 294 099 101 95 94 72 55 M.OOE-04 M.OOE-04 M.OOE-04 1.063 1.080 1.059 1.045 031 832 103 99 97 95 63 M. OOE-04 M.OOE-04 M.OOE-04 1.060 0.977 0.946 1.036 981 851 83 77 95 84 57 M. OOE-04 M.OOE-04 M.OOE-04 1.233 1.310 1.218 1.144 871 759 108 98 91 63 51 M.OOE-04 M.OOE-04 M.OOE-04 1.713 1.618 1.604 1.476 182 0.986 93 91 82 59 43 3.69E-05 M.OOE-04 M.OOE-04 1.593 1.762 1.150 1.108 014 1.035 59 55 46 48 3.77E-06 M.OOE-04 M.OOE-04

1.057 1.052 1.057 0.926 792 0.721 99 100 78 56 44 3.31E-05 M.OOE-04 M.OOE-04

The tables present the experimental data collected against each cell line. The first two columns describe the subpanel (e.g. leukaemia) and cell line (e.g. CCRF-CEM) involved. The next two columns list the Mean OD_tzero and Mean OD_ctrl; the next five columns list the Mean OD_test for each of five different concentrations. Each concentration is expressed as the log₁₀ (molar or μg/ml) . The next five columns list the calculated PGs for each concentration. The response parame¬ ters GI50, TGI, and LC50 are interpolated values representing the concentrations at which the PG is +50, 0, and -50, res¬ pectively. Sometimes these response parameters cannot be obtained by interpolation. If, for instance, all of the PGs in a given row exceed +50, then none of the three parameters can be obtained by interpolation. In such a case, the value given for each response parameter is the highest concentra¬ tion tested and is preceded by a ">" sign. This practice is extended similarly to the other possible situations where a response parameter cannot be obtained by interpolation.

The test compound could also be tested in an in vivo assay using a hollow fiber test system. This system consists of twelve selected human tumour cell lines encased in hollow fibers which are implanted into athymic nude mice. Six to eight days after administration of the test compound to the mice, the fibers are collected, the cells removed and growth inhibition is measured using MTT. Compounds which produce promising results in this assay may be selected for further in vivo evaluation using e.g. xenograft models.

Claims

1. Compounds of the general formula I

wherein

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, and R⁸ each independently are: hydrogen;

halogen;

nitro;

nitroso;

cyano;

a group -CO-Z-R¹⁰, -CS-Z-R¹⁰ or -SO₂-Z-R¹⁰ wherein Z is -O-, -S- or -N(R¹¹)-;

a group -C (NH)-NR¹⁰R¹¹;

a group -CO-R¹⁰, -SO-R¹⁰ or -SO₂-R¹⁰;

a group -Z-CO-R¹⁰, -Z-CO-Z-R¹⁰, -Z-CS-R¹⁰ or -Z-SO₂-R¹⁰ wherein each Z independently is as defined above;

a group -O-R¹⁰ or -S-R¹⁰;

a group -NR¹⁰R¹¹;

where groups R¹⁰ and R¹¹ each independently are hydrogen or is optionally substituted C_1-8alkyl, aryl, aryl-C_1-8alkyl where an alkyl group or moiety may be interrupted by -O-, -S- or -N(R¹⁴)- wherein R¹⁴ is hydrogen, C_1-8alkyl or aryl, and where the optional substituent (s) are selected from halogen, nitro, amidine, cyano, mercapto, C_1-8alkylthio, arylthio, hydroxy, C_1-8alkoxy, aryloxy, amino, C_1-8alkylamino, arylamino, diC_1-8alkylamino, diarylamino, formyl, C_1-8alkylcarbonyl, arylcarbonyl, C_1-8alkoxycarbonyl, aryloxycarbonyl, C_1-8alkylcarbonyloxy, aryloxycarbonyloxy, or two neighbouring substituents together form a bivalent group -Z-(C(R¹⁵)₂)_m-Z- wherein each Z independently is as defined above, R¹⁵ is hydrogen or C_1-2alkyl, and m is an integer from 1 to 3;

optionally substituted, linear or branched C_1-10alkyl, optionally substituted, linear or branched C_2-10alkenyl or C_4-10alkadienyl or C_6-10alkatrienyl, optionally substituted, linear or branched C_2-10alkynyl, or optionally substituted C_3-8cycloalkyl, C_3-8cycloalkenyl, C_4-8cycloal- kadienyl, C_6-8cycloalkatrienyl or C_3-8cycloalkyl-C_1-4alkyl where the optional substituent (s) are selected from halogen, nitro, cyano, -CO-Z-R¹⁰, -SO₂-Z-R¹⁰, -CO-R¹⁰, -SO-R¹⁰, -SO₂-R¹⁰, -Z-CO-R¹⁰, -Z-SO₂-R¹⁰, -O-R¹⁰, -S-R¹⁰, and -NR¹⁰R¹¹ wherein Z, R¹⁰ and R¹¹ are as defined above; aryl or aryl - C_{1 - 4} -alkyl where the aryl moiety may be substituted from 1 to 6 substituents selected from C_1-4- alkyl, halogen, nitro, nitroso, cyano, a group -CO-Z-R¹⁰, -CO-Z-R¹⁰, -SO₂-Z-R¹⁰, -CO-R¹⁰, -SO-R¹⁰, -SO₂-R¹⁰,

-Z-CO-R¹⁰, -Z-SO₂-R¹⁰, -O-R¹⁰, -S-R¹⁰, or -NR¹⁰R¹¹ wherein Z, R¹⁰ and R¹¹ are as defined above;

or R³ and R⁷ , and/or R⁴ and R⁸ together forms a bond;

or R¹ and R² , and/or R⁵ and R⁶ together forms a bivalent group - (CH₂)_n- wherein n is an integer from 3 to 5, or a bivalent group -Z-(C(R¹⁵)₂)_m-Z- wherein Z, R¹⁵ and m is as defined above; X¹ and X² each independently is O, S, or N(R¹²), wherein R¹² is a group as defined for R¹⁰; and

Y¹ and Y² each independently is N or C(R¹³) wherein R¹³ is a group as defined for R¹⁰ above; with the proviso that when X¹-Y¹ and X²-Y² are both O-N, and R³ and R⁷ together forms a bond, and R⁴ and R⁸ together forms a bond, then

at least one of R¹, R², R⁵, and R⁶ is different from hydrogen, or

R¹ and R⁶ are both different from nitro, methyl and unsubstituted phenyl; and physiologically acceptable salts thereof

2. Compounds according to claim 1 wherein X¹-Y¹ and X² -Y² are both O-N.

3. Compounds according to claim 1 or 2 wherein R³ and R⁷ together form a bond, and/or R⁴ and R⁸ together form a bond.

4. Compounds according to any of claims 1-3 wherein R² and R⁵ are both hydrogen.

5. Compounds according to any of claims 1-4 wherein R¹ and R⁶ independently are unsubstituted or substituted aryl groups, preferably phenyl substituted with one to four groups selected from hydroxy, halogen, amino, alkylamino, dialkyl- amino, mercapto, alkylthio, nitro, sulfonyl, C_1-8alkoxy, C_1-8alkyl-or arylcarbonyloxy, C_1-8alkyl- or arylcarbonylamino, C_1-8alkyl- or arylsulfonylamino, or two neighbouring substi- tuents together form a bivalent group -Z-(C(R¹⁵)₂)_m-Z-.

6. A compound according to any of claims 1-5 selected from

5,5'-bis- (3-(4''-hydroxyphenyl)-isoxazole),

5,5'-bis- (3-(2''-hydroxyphenyl)-isoxazole),

5,5'-bis- (3-(3''-hydroxyphenyl)-isoxazole),

5,5'-bis- (3-(2'',4''-dihydroxyphenyl)-isoxazole),

5,5'-bis- (3-(3'',4''-dihydroxyphenyl)-isoxazole),

5,5'-bis- (3-(3'',5''-dihydroxyphenyl)-isoxazole),

5,5'-bis- (3-(2 '',5''-dihydroxyphenyl)-isoxazole),

5,5'-bis- (3-(2'',3'',4''-trihydroxyphenyl)-isoxazole;

5,5'-bis- (3-(3'',4'',5''-trihydroxyphenyl)-isoxazole;

5,5'-bis- (3-(4''-methoxyphenyl)-isoxazole),

5,5'-bis- (3-(2''-methoxyphenyl)-isoxazole),

5,5'-bis- (3-(3 ''-methoxyphenyl)-isoxazole),

5,5'-bis- (3-(2'',4''-dimethoxyphenyl)-isoxazole),

5,5'-bis- (3-(3 '',4' '-dimethoxyphenyl)-isoxazole),

5,5'-bis- (3-(3'',5' '-dimethoxyphenyl)-isoxazole),

5,5'-bis- (3-(2'',5 ''-dimethoxyphenyl)-isoxazole),

5,5'-bis- (3-(2'',3' ',4''-trimethoxyphenyl)-isoxazole), 5,5 -bis- (3- (3'',4'',5''-trimethoxyphenyl)-isoxazole),

5,5 -bis- (3-(4''-acetoxyphenyl)-isoxazole),

5,5 -bis- (3- (2'' acetoxyphenyl)-isoxazole),

5, 5 -bis- (3- (3'' acetoxyphenyl)-isoxazole),

5,5 -bis- (3- (2'',4''-diacetoxyphenyl)-isoxazole),

5,5 -bis- (3- (3'',4''-diacetoxyphenyl)-isoxazole),

5,5 -bis- (3- (3'' 5''-diacetoxyphenyl)-isoxazole),

5,5 -bis- (3- (2'' 5''-diacetoxyphenyl)-isoxazole),

5,5 -bis- (3- (2'' 3'',4''-triacetoxyphenyl)-isoxazole),

5,5 -bis- (3- (3'' 4'',5''-triacetoxyphenyl)-isoxazole),

5,5 -bis- (3- (4''-benzyloxyphenyl)-isoxazole),

5,5 -bis- (3- (2''-benzyloxyphenyl)-isoxazole),

5,5 -bis- (3- (3''-benzyloxyphenyl)-isoxazole),

5,5 -bis- (3- (2'',4''-dibenzyloxyphenyl)-isoxazole),

5,5 -bis- (3- (3'',4''-dibenzyloxyphenyl)-isoxazole),

5,5 -bis- (3-(3'',5''-dibenzyloxyphenyl)-isoxazole),

5,5 -bis- (3- (2'',5''-dibenzyloxyphenyl)-isoxazole),

5,5 -bis- (3- (2'',3'',4''-tribenzyloxyphenyl)-isoxazole),

5,5 -bis- (3- (3'',4'',5''-tribenzyloxyphenyl)-isoxazole),

5,5 -bis- (3- (3''-hydroxy-4''-methoxyphenyl)-isoxazole),

5,5 -bis- (3- (4''-hydroxy-3''-methoxyphenyl)-isoxazole),

5,5 -bis- (3- (3'',4''-methylendioxyphenyl)-isoxazole),

5,5 -bis- (3- (3'',4''-(2,2-propylendioxy)phenyl)-isoxazole),

5,5 -bis- (3- (4''-nitrophenyl)-isoxazole),

5,5 -bis- 3- (4''-aminophenyl)-isoxazole),

5,5 -bis- 3- (4''-acetaminophenyl)-isoxazole),

5,5 -bis- 3- (4''-chlorophenyl)-isoxazole),

5,5 -bis- 3- (4''-bromophenyl)-isoxazole),

5,5 -bis- 3- (4''-iodophenyl)-isoxazole),

5,5 -bis- 3- (4''-sulfonylphenyl)-isoxazole),

5,5 -bis- 3- (4''-amidinophenyl)-isoxazole), and

5.5 -bis- 3- (4''-carboxyphenyl)-isoxazole). 3

7. A compound of the general formula I as defined in claim 1 which, when tested against a mammalian cancer cell line in accordance with the standard procedure of the National Cancer Institute in vitro Anticancer Drug Discovery Screen, results in a Percentage Growth (PG), as defined herein, below 90, preferably 80, in particular 70, especially 60, such as 50.

8. A compound of the general formula I as defined in claim 1 which, when tested against a mammalian cancer cell line in accordance with the standard procedure of the National Cancer Institute in vi tro Anticancer Drug Discovery Screen, exhibits a Response Parameter GI50 value, as defined herein, at a concentration of at the most 10^-4 M with respect to at least one mammalian cancer cell line.

9. A compound of the general formula I as defined in claim 1 which, when tested against a mammalian cancer cell line in accordance with the standard procedure of the National Cancer Institute in vi tro Anticancer Drug Discovery Screen, does not exhibit a LC50 value, as defined herein, at a concentration of below 10^-4 M.

10. A pharmaceutical composition comprising at least one of the compounds of the general formula I'

wherein

R¹, R², R³, R ⁴ ,R⁵, R⁶, R⁷, and R ⁸ eaich independently are: hydrogen;

halogen;

nitro;

nitroso;

cyano;

a group -CO -Z- R¹⁰, -CS -Z-R¹⁰ or -SO₂ - Z - R¹⁰ wherein Z is

-O-, -S- or -N(R¹¹) -;

a group -C(NH)-NR¹⁰R¹¹; a group - CO - R¹⁰ , - SO - R^{1 0} or - SO₂ - R¹⁰ ;

a group -O-R¹⁰ or -S-R¹⁰;

a group -NR¹⁰R¹¹;

where groups R¹⁰ and R¹¹ each independently are hydrogen or is optionally substituted C_1-8alkyl, aryl, aryl-C_1-8alkyl where an alkyl group or moiety may be interrupted by -O-, -S- or -N(R¹⁴)- wherein R¹⁴ is hydrogen, C_1-8alkyl or aryl, and where the optional substituent (s) are selected from halogen, nitro, amidine, cyano, mercapto, C_1-8alkylthio, arylthio, hydroxy, C_1-8alkoxy, aryloxy, amino, C_1-8alkylamino, arylamino, diC_1-8alkylaird.no, diarylamino, formyl, C_1-8alkylcarbonyl, arylcarbonyl, C_1-8alkoxycarbonyl, aryloxycarbonyl, C_1-8alkylcarbonyloxy, aryloxycarbo- nyloxy, or two neighbouring substituents together form a bivalent group -Z-(C(R¹⁵)₂)_m-Z- wherein each Z independently is as defined above, R¹⁵ is hydrogen or C_1-2alkyl, and m is an integer from 1 to 3;

optionally substituted, linear or branched C_1-10alkyl, optionally substituted, linear or branched C_2-10alkenyl or C_4-10alkadienyl or C_6-10alkatrienyl, optionally substituted, linear or branched C_2-10alkynyl, or optionally substituted C_3-8cycloalkyl, C_3-8cycloalkenyl, C_4-8cycloal- kadienyl, C_6-8cycloalkatrienyl or C_3-8cycloalkyl-C_1-4alkyl where the optional substituent (s) are selected from halogen, nitro, cyano, -CO-Z-R¹⁰, -SO₂-Z-R¹⁰, -CO-R¹⁰, -SO-R¹⁰, -SO₂-R¹⁰, -Z-CO-R¹⁰, -Z-SO₂-R¹⁰, -O-R¹⁰, -S-R¹⁰, and -NR¹⁰R¹¹ wherein Z, R¹⁰ and R¹¹ are as defined above; aryl or aryl -C_1-4-alkyl where the aryl moiety may be substituted from 1 to 6 substituents selected from C_1-4- alkyl, halogen, nitro, nitroso, cyano, a group -CO-Z-R¹⁰, -CO-Z-R¹⁰, -SO₂-Z-R¹⁰, -CO-R¹⁰, -SO-R¹⁰, -SO₂-R¹⁰,

or R³ and R⁷, and/or R⁴ and R⁸ together forms a bond; or R¹ and R², and/or R⁵ and R⁶ together forms a bivalent group - (CH₂)_n- wherein n is an integer from 3 to 5, or a bivalent group -Z-(C(R¹⁵)2₂)_m-Z- wherein Z, R¹⁵ and m is as defined above; X¹ and X² each independently is O, S, or N(R¹²), wherein R¹² is a group as defined for R¹⁰ above; and

Y¹ and Y² each independently is N or C(R¹³) wherein R¹³ is a group as defined for R¹⁰ above; in combination with a pharmaceutically acceptable carrier.

11. The compounds of the general formula I' as defined in claim 10 for use in therapy, in particular in the treatment of cancer.

12. A method for the treatment of cancer in human beings or animals, said method comprising administering to a human being or animal in need thereof an effective amount of a compound of the general formula I' as defined in claim 10.

13. The use of a compound of the general formula I' as defined in claim 10 in the manufacture of a medicament for use in the treatment of cancer.