WO1991004967A1

WO1991004967A1 - Compounds useful for measuring low levels of sulfonylureas by immunoassay

Info

Publication number: WO1991004967A1
Application number: PCT/US1990/005274
Authority: WO
Inventors: Bruce Lawrence Finkelstein; Janice Kay Sharp
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1989-10-06
Filing date: 1990-09-21
Publication date: 1991-04-18
Anticipated expiration: 1992-04-06
Also published as: EP0494973A1; IE890149L; AU6548890A; JPH05500957A

Abstract

Sulfonylurea carboxylic acids, their protein conjugates, and polyclonal antibodies produced in response to these conjugates are useful, particularly in kit form, for measuring the presence of very low levels of sulfonylurea herbicides and their derivatives in an enzyme-linked immunosorbent assay.

Description

TITLE

COMPOUNDS USEFUL FOR MEASURING LOW LEVELS OF SULFONYLUREAS BY IMMUNOASSAY

Background of the Invention Field of the Invention

This invention pertains to certain sulfonylurea carboxylic acids which have been found useful in an enzyme-linked immunoabsorbent assay (ELISA) technique for determining the presence of even very low levels of sulfonylurea compounds in ground water and other matrices. This invention also concerns protein conjugates of sulfonylurea carboxylic acids,

antibodies produced in response thereto and an ELISA kit for determining the presence of sulfonylureas at low levels. State of the Art

Each of the following publications describes sulfonylureas whose presence can be detected by the improved ELISA method of this invention or conjugated to proteins according to the teachings herein and employed in said ELISA:

U.S. 4,394,506 U.S. 4,394,506

U.S. 4,481,029 EPA 87,780

EP 95,925 EPA 161,211

U.S. 4,435,206 Japan 63/166,803A

U.S. 4,522,645 U.S. 4,684,395

U.S. 4,420,325 EP 87,780A.

DE 3,016,831 discloses synthesis of conjugates of simple peptides and other organic compounds, but not sulfonylurea-derived compounds.

The ELISA procedure is a well-known method for detecting pesticide residues in the parts per billion range in soil or water; Wie et al., J. Agric. Food Chem., 32, (1984) pages 1294 to 1301.

Kelley et al., J. Agric. Food Chem.g 33, (1985) pages 962 to 965 disclose a sulfonylurea immunoassay using an ELISA technique.

Synthesis of conjugates often used in

immunoassays is described in "The Handbook of

Experimental Immunology," 4th Ed., Vol. I,

"Immunochemistry", Weir, Ed. Chapter 3, "Haptens and Carriers," Makela et al., Blackwell Scientific

Publications, Oxford, 1986.

An ELISA technique relies on the specific interaction of the antibody molecule with substances called antigens. The introduction of an antigen into the body of a vertebrate animal triggers the animal's immune system to generate antibodies that will bind the antigen. To be an effective antigen, a molecule must have two attributes. It must have a site that can bind to the cell-surface antibody of a virgin B cell and it must have a site that promotes cell-cell interactions between various cells of the immune system. Smaller molecules (haptens) such as the sulfonylureas seldom have both of these attributes and are generally not good antigens. To overcome this problem, haptens are generally covalently linked to proteins, called Qarriers, which provide the sites that promote cell-cell interactions in the immune system. The immunized animal's response to such hapten-carrier-protein antigens is polyclonal. Other relevant factors in an ELISA technique will be described hereafter in relation to this invention.

Immunoassays for pesticides have been in the literature for a number of years (Van Emon et al., Analytical Methods for Pesticides and Plant Growth Regulators, Vol. XCII, 1989, pp. 217 to 263). Many analytical methods have been developed for clinical monitoring of pesticide exposure, primary among them are the Enzyme Immunoassays (EIA). Because

pesticides are small molecules, usually of molecular weights between 100 and 1000, they alone do not induce the immune response and must be attached to larger proteins. Essential to the design of these methods has been the hapten which resembles the compound of interest but which contains an additional functional group for the attachment of the hapten to the protein; and the immunogen, which must be

selected to give optimum immune response and antigen recognition.

Summary of the Invention

This invention concerns certain of the

compounds of Formula I, protein conjugates of the compounds of Formula I, and the polyclonal antibodies produced by the exposure of mammals to the conjugates.

This invention also concerns an ELISA method for measuring very low concentrations of

sulfonylureas (the "analytes"), e.g., from less than 10 up to 10,000 picograms per milliliter (pg/mL).

This invention also concerns kits for the measurement of sulfonylureas comprising coating- conjugate-coated solid phase and sufficient

quantities of premeasured first antibody, second

(labeled) antibody, enzyme substrate, and control samples.

The compounds of this invention are herbicidal sulfonylureas or derivatives, with a carboxylate group added to any methyl, methylene or methine carbon of said sulfonylurea that results in a

water-stable compound, said carboxylate being tethered with a 0-3 atom chain wherein the chain is made up of carbon atoms, and, if the tether is 2 or three atoms, one can be a sulfur, nitrogen or oxygen atom.

Compounds useful in the improved ELISA method of this invention comprise compounds of Formula I, including their agriculturally suitable salts:

wherein J is

G is H or MO₂C (alkyl)_nL;

n is 0 or 1;

alkyl is 1 to 3 carbon atoms optionally

substituted with one or two of halogen, methyl, methoxy, or methylthio;

L is O, S, NR⁵, -N(C=O)- or a direct bond;

R, R⁴ and R⁵ are independently H or CH₃;

E is a single bond or CH₂;

R¹ is H, C₁ to C₃ alkyl, C₁ to C₃ haloalkyl, halogen, nitro, C₁ to C₃ alkoxy, SO₂NR^aR^b, CONR^aR^b, C₁ to C₃ alkylthio, C₁ to C₃

alkylsulfinyl, C₁ to C₃ alkylsulfonyl,

CH₂CN, CN, CO₂R^c, C₁ to C₃ haloalkoxy, C₁ to C₃ haloalkylthio, C₂ to C₄ alkoxyalkyl, C₃ to C₄ alkoxyalkoxy, C₂ to C₄ alkylthioalkyl, CH₂N₃, NR^dR^e, or Q;

R² is H, C₁ to C₃ alkyl, C₁ to C₃ haloalkyl, halogen, nitro, C₁ to C₃ alkoxy, C₁ to C₃ alkylthio, CN, C₁ to C₃ haloalkoxy, or C₂ to C₄ alkoxyalkyl;

R^a is H, C₁ to C₄ alkyl, C₂ to C₃ cyanoalkyl, methoxy or ethoxy;

R^b is H, C₁ to C₄ alkyl or C₃ to C₄ alkenyl; or R^a and R^b may be taken together as -(CH₂)₃-,

-(CH₂)₄-, -(CH₂)₅- or -CH₂CH₂OCH₂CH₂-;

R^c is C₁ to C₄ alkyl, C₃ to C₄ alkenyl, C₃ to C₄ alkynyl, C₂ to C₄ haloalkyl, C₂ to C₃ cyanoalkyl, C₅ to C₆ cycloalkyl, C₄ to C₇ cycloalkylalkyl or C₂ to C₄ alkoxyalkyl;

R^d and R^e are independently H or C₁ to C₂ alkyl; Q is a saturated 5- or 6-membered ring

containing one heteroatom selected from 0, S, or N, tetrazole optionally substituted with C₁-C₃ alkyl, or an unsaturated 5- or 6-membered ring containing 1 to 3

heteroatoms selected from 0-1 S, 0-1 0 or 0-3 N and when Q is an unsaturated 5- or 6-membered ring, it may optionally be substituted by one or more groups selected from C₁ to C₄ alkyl, halogen, C₃ to C₄ alkenyl, C₁ to C₃ alkoxy, C₁ to C₃

alkylthio, C₃ to C₄ alkenylthio, C₁ to C₂ haloalkoxy or C₁ to C₃ haloalkylthio;

X is H, C₁ to C₄ alkyl, C₁ to C₄ alkoxy,

C₁ to C₄ haloalkoxy, C₁ to C₄ haloalkyl, halogen, C₂ to C₅ alkoxyalkyl, C₂ to C₅ alkoxyalkoxy, amino, C₁ to C₃ alkylamino, di(C₁ to C₃ alkyl) amino or C₃ to C₅

cycloalkyl; or C₁ to C₄ alkyl, C₁ to C₄ alkoxy or C₁ to C₄ haloalkoxy substituted on the alkyl, alkoxy or haloalkoxy group with CO₂M;

Y is H, C₁- to C₄ alkyl, C₁ to C₄ alkoxy, C₁ to C₄ haloalkoxy, C₂ to C₅ alkoxyalkyl, C₂ to C₅ alkoxyalkoxy, amino, C₁ to C₃ alkylamino, di(C₁ to C₃ alkyl)amino, or C₁ to C₄ alkyl;

M is H or an alkali or alkaline earth metal

salt;

R³ is H or C₁ to C₃ alkyl;

Z is CH, N or CCO₂M; and

E¹ is a direct bond or CH₂.

Compounds of this invention are those of

Formula I wherein :

(i) when G is not H and when L is a direct bond, then n = 1;

(ii) when G is H, then J is J-1, J-4 or J-5;

(iii) when G is H and J is J-4 or J-5, then X is C₁ to C₄ alkyl, C₁ to C₄ alkoxy, or C₁ to C₄ haloalkoxy substituted with CO₂M; (iv) when G is H, and J is J-1, then E is CH₂, and X is C₁ to C₄ alkyl, C₁ to C₄ alkoxy, or C₁ to C₄ haloalkoxy substituted with CO₂M; and

(v) when J is J-1, G is 3-CO₂H, X is CH₃ and Y is OCH₃, then Z is not N.

The preferred ELISA method of this invention employs compounds of the following formulae:

The conjugates of this invention comprise the compounds of Formula I bound, through a carboxyl group, to proteins that are capable of eliciting an immune response in at least one mammal selected from: mice, rabbits, goats, dogs, horses, sheep, guinea pigs, chickens, hamsters, and rats. Any protein or molecule whose introduction into an animal can lead to T-cell proliferation and differentiation can be used as a carrier protein or its equivalent. Examples of proteins useful in immunogen synthesis are keyhole limpet hemocyanin (KLH), pumpkin seed globulin (PSG), marijuana seed globulin (MSG), ovalbumin (OVA), or serum albumin from cows (BSA), rabbits, or mice.

The coating conjugates of this invention are independently characterized by their ability to adhere to the solid phase employed in Step B of the method described hereafter and their ability to complex with the antibody of Step A. By "coating conjugate" is meant a hapten chemically conjugated to a protein, sometimes called "coating antigen".

Preferred coating conjugates are compounds selected from 1 to 12 covalently linked by methods described herein to keyhole limpet hemocyanin, bovine serum albumin, and ovalbumin. Other useful proteins will suggest themselves to one skilled in the art.

The antibodies of the invention are polyclonal antibodies produced by mammals in response to the injection of sulfonylurea-protein conjugates

described above. These antibodies bind with high affinity to the conjugate described herein and to the sulfonylurea that is the subject of the ELISA.

The improved enzyme-linked immunosorbent assay for detecting the presence of a sulfonylurea in an unknown sample comprises the steps:

(A) formir a complex of the sulfonylurea with an excess of a first antibody of known concentration,

(B) complexing the unbound first antibody from Step A with a coating conjugate adhered to a solid phase. (C) binding a labeled antibody to the antibody-conjugate complex of B, and (D) determining the presence and the amount of sulfonylurea in the unknown sample by measuring the amount of unbound antibody in Step A with reference to controls which comprise known concentrations of the sulfonylurea;

wherein the improvement comprises (i) employing a conjugate of this invention as an immunogen to generate the antibody in Step A; and (ii) employing the same or a different conjugate of this invention as coating conjugate in Step B.

This invention also concerns a test kit, comprising the ingredients necessary to run an ELISA measurement on target sulfonylureas. The test kit has these components:

(i) an antibody to the sulfonylurea in the unknown;

(ii) a solid phase having a coating conjugate bound to it;

(iii) a labeled antibody that recognizes antibody (i);

(iv) a developer that develops color in the presence of a label; and

(v) controls comprising at least one known concentration of the sulfonylurea and one containing no sulfonylurea; whereby the components cooperate so that i, ii and iii are contacted with each other and, upon addition of iv, develop a color which indicates, upon comparison to the controls, the presence and concentration of the target sulfonylurea.

Using the procedures and the kit described herein, the following sulfonylurea herbicides can be detected: 2-chloro-N-[(4-methoxy-6-methyl-1,3,5-triazin-2- yl)amino]carbonyl]benzenesulfonamide

(chlorsulfuron)

methyl 2-[[[[(4,6-dimethyl-2-pyrimidinyl)amino]- carbonyl]amino]sulfonyl]benzoate

(sulfometuron methyl)

methyl 2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2- yl)amino]carbonyl]amino]sulfonyl]benzoate

(metsulfuron methyl)

2-[[N-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-N- methylamino]carbonyl]amino]sulfonyl]benzoic acid, methyl ester

(tribenuron methyl)

ethyl 2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl),

amino]carbonyl]amino]sulfonyl]benzoate

(chlorimuron ethyl)

2-[[(4-ethoxy-6-methylamino-1,3,5-triazin-2- yl)aminocarbonyl]aminosulfonyl]benzoic acid, methyl ester

(ethametsulfuron methyl)

2-[[(4,6-dimethoxy-1,3,5-triazin-2-yl)aminocarbonyl]- aminosulfonyl]-4-(2,2,2-trifluoroethoxy)benzoic acid, ethyl ester

4-chloro-2-[[(4-methoxy-6-methyl-1,3,5-triazin-2- yl)aminocarbonyl]aminosulfonyl]benzoic acid, isopropyl estec

3-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]- carbonyl]amino]sulfonyl]-2-thiophene carboxylic acid, methyl ester

(thifensulfuron methyl)

methyl 2-[[[[(4,6-dimethoxy-2-pyrimidinyl)amino]- carbonyl]amino]sulfonyl]methylbenzoate

(bensulfuron methyl)

2-[[(4,6-dimethoxypyrimidin-2-yl)aminocarbonyl]- aminosulfonyl]N,N-dimethyl-3-pyridinecarboxamide 2-[[(4,6-dimethoxypyrimidin-2-yl))aminocarbonyl]- aminosulfonyl]-3-pyridinecarboxylic acid, methyl ester

N-[(4,6-dimethoxypyrimidin-2-yl))aminocarbonyl]-3-

(ethylsulfonyl)-2-pyridinesulfonamide

N-[(4,6-dimethoxypyrimidin-2-yl))aminocarbonyl]- 2,3-dihydro-2-methyl-benzo(b)thiophene-7- sulfonamide, 1,1 dioxide

2-[[[[(4,6-bis(difluoromethoxy)-2-pyrimidinyl]- amino]carbonyl]amino]sulfonyl]benzoic acid, methyl ester

ethyl 5-[3-(4,6-dimethoxypyrimidin-2-yl)ureido- sulfonyl]-1-methylpyrazole-4-carboxylate

N-[(6-methoxy-4-methy1-1,3,5-triazin-2-yl)aminocarbonyl]-2-(2-chloroethoxy)benzene sulfonamide N-1(4,6-dimethoxy-1,3,5-triazin-2-yl)amino-carbonyl]- 2-(2-methoxyethoxy)benzenesulfonamide

N-[(4,6-dimethoxypyrimidin-2-yl)-amino]carbonyl]- 3-trifluoromethyl-2-pyridinesulfonamide.

Preferred sulfonylurea target pesticides are chlorsulfuron, bensulfuron methyl, metsulfuron methyl and chlorimuron ethyl. The method for using the kit to detect the target sulfonylurea comprises

contacting components i, ii, iii and iv and comparing the color that is developed to controls, v, thereby determining the presence and concentration of the target sulfonylurea.

Details of the Invention

Synthesis

Compounds of Formula I can be synthesized by reaction of sulfonamides with the phenyl ester of the appropriate carbamic acid in the presence of an equimolar quantity of a tertiary amine base such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as shown in Equation 1.

equation 1

JSO₂NH₂ +

Sulfonamides of Formula II and sulfonyl chlorides of Formula III are defined below:

D = NH₂ or Cl D = NH₂ or Cl

D = NH₂ or Cl

I I D = NH₂ ;

I I I D = Cl .

Sulfonamides of Formula II can be converted to homologated sulfonamides of Formula IV by procedures such as those shown in Equation 1 according to the methods reviewed in Neier and Zeller, Angew. Chem. Inc. Ed. Engl., 14, (1975) pages 32 to 43; or

Equation 2 according to the methods reviewed in

Johnson, "Ylid Chemistry," Academic Press, New York, 1966; or by other methods known to one skilled in the art.

Equation 1 H₂NO₂S-Ar-L(alkyl)_nCO₂H

II

H₂NO₂S-Ar-L(alkyl)_nCH₂CO₂H (1) IV [H]

H₂NO₂S-Ar-L(alkyl)_nCO₂H H₂NO₂S-Ar-L(alkyl)_nCHO

Equation 2

Ph₃P=CH(CH₂)_nCO₂H

H₂NO₂S-Ar-L(alkyl)_nCH=CH(CH₂)_nCO₂H (2)

[H]

H₂NO₂S-Ar-L(alkyl)_n-CH₂CH₂(CH₂)_nCO₂H

where n = 0, 1.

Sulfonamides of Formula II can also be prepared as shown in Equations 3 and 4 according to the

methods described in Patai, "Chemistry of the Ether Linkage Interscience," New York, 1967 and Reid,

"Organic Chemistry of Bivalent Sulfur," Vol. 1,

Chemical Publishing Company, New York, 1958, or by other methods known to one skilled in the art.

Equation 3

Base

H₂NO₂SArSH + BrCH₂(alkyl)_nCO₂H

H₂NO₂SArS-CH₂(alkyl)_nCO₂H (3)

II

Equation 4

Base

H₂NO₂SArOH + BrCH₂(alkyl)_nCO₂H

H₂NO₂SArO-CH₂(alkyl)_nCO₂H (4)

II Sulfonamides of Formula II can also be prepared from suitably activated aromatics by the methods shown in Equation 5 such as those reviewed in

Zoltewicz, Top. Curr. Chem., 59, (1975) page 33 or by other methods known to one skilled in the art.

Equation 5 HO₂C-(alkyl)_nL

H₂NO₂S-Ar-halogen

H₂NO₂S-Ar-L(alkyl)_nCO₂H (5) Sulfonamides of Formula II can also be prepared by the methods shown in Equation 6 (where L is O, NH or S) or by other methods known to one skilled in the art.

Equation 6

H₂NO₂S-Ar-LH

H₂NO₂S-Ar- L-C( O) ( CH₂) _nCH₂CO₂H ( 6) The preparation of sulfonamides from sulfonyl chlorides is widely reported in the literature; for reviews see Hawking et al., "The Sulfonamides," Lewis and Co., London, 1950 and Northey, "The Sulfonamides and Allied Compounds," Reinhold Publishing Corp., New York, 1948.

Additionally, primary sulfonamides, such as those of Formula II, can be formed by removal of an N-t-butyl protecting group from the corresponding secondary sulfonamide with trifluoroacetic acid, Catt et al., J. Pro. Chem., 39 (1974), 566 or

polyphosphoric acid, Lombardino, J. Org. Chem., 36 (1971), 1843.

The requisite sulfonyl chlorides of Formula III can be synthesized by known methods or with slight modifications thereof, by one skilled in the art.

Several representative teachings are listed below.

Aromatic nitro groups can be transformed into sulfonyl chlorides by reduction, diazotization and coupling with sulfur dioxide/cupric chloride as taught in U.S. Patent 4,310,346.

European Publication No. 94,821 discloses the displacement of aromatic halides with thiolate anions and subsequent oxidative chlorination to yield sulfonyl chlorides.

Halogen-metal exchange of aromatic halides or proton-metal exchange of aromatics followed by quenching with sulfur dioxide gives sulfinate salts. these salts yield sulfonyl chlorides upon reaction with N-chlorosuccinimide as taught in U.S. Patent 4,481,029. Directed proton-metal exchange of

aromatic compounds has been reviewed by Gschwend and Rodriguez, Org. Reactions, 26 (1979), 1. Directed lithiation of aryl-N-i-butylsulfonamides is described by Lombardino, J. Org. Chem., 36 (1971), 1843. Also, aryllithiums may be converted directly to

arylsulfonyl chlorides with sulfuryl chloride as described in Bhattacharya et al., J. Chem. Soc. C.,

(1968), 1265.

Electrophilic chlorsulfonation of an aromatic ring to give a sulfonyl chloride is well known in the literature. This technique works best for alkyl aryl ethers and alkyl aromatics. Its application is described by Huntress et al., J. Am. Chem. Soc., 62

(1940), 511 to 14 and 603 to 4.

Transformation of phenols to sulfonyl chlorides can be accomplished by the formation of a

thiocarbamate, rearrangement, hydrolysis and

oxidative chlorination as described by Newman et al.,

J. Org. Chem., 31 (1966), 3980. PROCEDURE A

3-Chloro-4[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)- aminocarbonyl]aminosulfonyl]benzoic acid

(Compound 8)

To a solution of 2.00 g (8.5 mmol) of

4-aminosulfonyl-3-chlorobenzoic acid and 2.20 g (8.5 mmol) of phenyl 4-methoxy-6-methyl-1,3,5-triazin-2-yl- carbamate in 45 mL of acetonitrile was added 2.54 mL (17 mmol) of 1,8-diazabicyclo[5.4.0]undec-7-ene dropwise. The reaction mixture was stirred for 2 hours. 45 mL of water was added. Upon the dropwise addition of 25 mL of 1N HCl, a precipitate formed. The solid was filtered off and dried to give 2.05 g of the title compound as a white solid; m.p. 132 to 136°C. PROCEDURE B 2-Amino-1,4-benzenedicarboxylic acid, 1-methyl

ester

A solution of 7.0 g of 2-nitro-1,4-benzene- dicarboxylic acid, 1-methyl ester (prepared according to Ger. Offen 3,001,695, CA. 95: 132525w) and 3.5 g of 10% palladium on carbon was placed under 50 psig of hydrogen for 16 hours. The solution was

filtered. The filtrate was evaporated to give 5.3 g of the title compound as a yellow solid; m.p. 164 to 167°C.

PROCEDURE C

2-(t-Butylaminosulfonyl)-1,4-benzenedicarboxylic

acid, 1-methyl ester

The compound of Procedure B, 2.0 g (10.9 mmol) was slurried in 5 mL of acetic acid. With cooling, 20 mL of concentrated HCl was added. The reaction mixture was cooled to -10°C and a solution of 0.83 g (12 mmol) of sodium nitrite was added dropwise. The reaction mixture was stirred 20 minutes.

This solution was poured into a flask

containing 50 mL of acetic acid, 0.5 g CuCl and 4 mL of liquified sulfur dioxide at 0°C. After stirring 2 hours, the reaction was extracted with dichloromethane. The organic layer was dried and all of the volatiles were removed with a rotary evaporator .

The residue was dissolved in 150 mL of

dichloromethane and cooled to -78°C. 8 mL of t-butylamine was added dropwise. The reaction was allowed to warm to room temperature. It was washed with water, dried and the solvent was removed with a rotary evaporator. This procedure gave 2.3 g of the title compound as a tan solid; m.p. 165 to 171°C.

PROCEDURE D

2-(Aminosulfonyl)-1,4-benzenedicarboxylic acid,

1-methyl ester

To 2.0 g of the material from Procedure C was added 20 mL of trifluόroacetic acid. The solution was stirred for 2 hours. The volatiles were removed with a rotary evaporator. The residue was triturated with 1-chlorobutane to give 1.5 g of the title compound as a tan solid; m.p. 211 to 216°C.

PROCEDURE E

2-[[(4-Methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbonyl]aminosulfonyl]-1,4-benzenedicarboxylic, 1-methyl ester (Compound 3) By the procedure given in Procedure A, 1.00 g of the material of Procedure D was converted to 1.25 g of the title compound as a white solid; m.p. 165 to 169°C(d). PROCEDURE F

2-[[(4-Ethoxy-6-(methylamino)-1,3,5-triazin-2-yl]- aminocarbonyl]aminosulfonyl]-1,4-benzenedicarboxylic acid, 1-methyl ester (Compound 9)

By the procedure given in Procedure A, 200 mg of the material from Procedure D was reacted with 235 mg of phenyl 4-ethoxy-6-methylamino-1,3,5- triazin-2-yl-carbamate to give 250 mg of the title compound as a white solid; m.p. 202 to 205°C.

PROCEDURE G

2-[[(4 ,6-Dimethyl-1,3,5-triazin-2-yl)aminocarbonyl]- aminosulfonyl]-1,4-benzeneflicarboxylic acid,

1-methyl ester (Compound 10)

By the procedure in Procedure A, 200 mg of the material from Procedure D was reacted with 190 mg of phenyl 4,6-dimethylρyrimidin-2-yl-carbamate to give 120 mg of the title compound as a white solid; m.p. 145 to 150°C.

PROCEDURE H

2-[[(4-Chloro-6-methoxypyrimidin-2-yl)aminocarbonyl] aminosulfonyl]-1,4-benzenedicarboxylic acid,

1-ethyl ester (Compound 4) By the procedure given in Procedure A, 1.0 g of 2-(aminosulfonyl)-1,4-benzenedicarboxylic acid,

1-ethyl ester and 1.03 g of phenyl 4-chloro-6-methoxy- pyrimidin-2-yl-carbamate were reacted to give 90 mg of the title compound as a white solid; m.p. 125 to 128°C.

PROCEDURE I

Phenylmethyl 2-(4-amino-6-methoxy-1,3,5-triazin-2- ylosy)-propanoate

A 33 g (83 mmol) portion of 60% sodium hydride in mineral oil was washed with hexanes and 75 mL of THF was added. After cooling to 0°C, 15 g (83 mmol) of phenylmethyl 2-hydroxypropanoate was added

dropwise. After 1 hour at room temperature, the reaction mixture was cooled to 0°C. 7 g (44 mmol) of 4-chloro-6-methoxy-pyrimidin-2-yl-amine was added portionwise over a 15 minute period. After stirring 16 hours at room temperature, dichloromethane was added to the reaction. It was washed with water, dried and the volatiles were removed with a rotary evaporator.

Half of the residue was purified by flash chromatography to give 5.5 g of the title compound as a glass, which solidified upon standing; m.p. 87 to 92°C.

PROCEDURE J 1-Phenylmethyl 2-[N-phenylcarbamoyl)-4-amino-6- methoxv-1,3,5-triazin-2-yloxy]prooanoate

To a solution of 5.0 g (17 mmol) of the

material from Procedure I in 90 mL THF at -78°C 2.4 mL (19 mmol) of phenylchloroformate was added. 38 mL (38 mmol) of a 114 solution of lithium

bis (trimethylsilyl) amide was added dropwise over 30 minutes. After stirring for 15 minutes at -78°C, the reaction was allowed to warm to -25°C. 2.2 mL of acetic acid was added. The reaction mixture was poured into ice/water, made acidic with acetic acid and extracted with ether. The organic layer was dried and the solvent was removed with a rotary evaporator.

The residue was purified by flash

chromatography to give 4.34 g of the title compound as a gummy white solid. IR (KBr) 1755, 1790 cm^-1.

1H-NMR (CDCl₃) δ 1.64 (d, 3), 3.93 (s, 3), 5.17 (d, 2), 5.35 (q, 1), 7.27 (m, 10), 7.9 (s, 1).

PROCEDURE K

Methyl 2-[[[[4-(1-carboxyethoxy)-6-methoxy- 1,3,5-triazin-2-yl]aminocarbonyl]aminosulfonyl]- methyl]benzoate (Compound 11)

By the procedure given in Procedure A, 1.77 g (4.4 mmol) of the material from Procedure J was reacted with 1.0 g (4.4 mmol) of methyl

2-aminosulfonylmethylbenzoate. No precipitate was obtained so the reaction was extracted with

dichloromethane. The organic layer was dried and the organics were removed with a rotary evaporator.

Half of the residue was dissovled in 40 mL of ethanol. One gram of 10% palladium on carbon was added. The reaction mixture was placed under 50 psig of hydrogen for 2 hours. After filtration the volatiles were removed with a rotary evaporator. The residue was triturated with 1-chlorobutane to give 200 mg of the title compound as a white solid; m.p. 152°C(d).

PROCEDURE L

2-[4-[[[3-[(Dimethylamino)carbonyl]-2-pyridinyl- sulfonyl]aminocarbonyl]amino]-6-methoxy-1,3,5- triazin-2-yloxy]propanoic acid (Compound 1) By the procedure given in Procedure A, 1.22 g

(2.90 mmol) of the material from Procedure J and 0.66 g (2.9 mmol) 2-(aminosulfonyl)-N,N-dimethyl-3- pyridinecarboxamide was reacted to give 80 mg of the title compound as a white solid; m.p. 135 to 140°C.

Using Procedures A to L described above, the compounds in Tables 1 to 8 can be prepared. General Formula for Tables 1-8

Melting points (in °C) of compounds footnoted in the Tables are as follows with the number before the / indicating the footnote number: 1/165 to

169(d), 2/202 to 205, 3/125 to 128, 4/145 to 150, 5/207 to 212, 6/157 to 158, 7/147 to 148, 8/130(d), 9/163 to 164(d), 10/142 to 145(d), 11/154 to 157, 12/177 to 178(d), 13/142 to 144(d), 14/142 to 144(d), 15/207 to 209(d), 16/173 to 175, 17/155 to 157(d), 18/162 to 164(d), 19/155 to 156, 20/135 to 137,

21/148 to 150, 22/143 to 145, 23/200 to 202, 24/195 to 199, 25/192 to 194, 26/178 to 182, 27/139 to 142, 28/167 to 171, 29/145 to 150, 30/165, 31/132 to 136, 32/156 to 158, 33/152(d), 34/176 to 182, 35/182 to 187(d), 36/161 to 162.5, 37/142 to 145, 38/195 to 197, 39/198 to 201, 40/132 to 135 and 41/135 to 140.

Synthesis of Conjugates

The procedure for synthesis of protein

conjugates with the sulfonylurea carboxylic acid (hereafter referred to as the analyte) entails activation by means of a carboxyl-activating reagent (CAR) such as 1-(3-dimethylaminoρropyl)-3-ethyl- carbodiimide hydrochloride or disuccinimidyl

carbonate followed by reaction of the activated carboxylic acid so obtained with the amines (lysines) of a protein. This process results in the attachment of the analyte to the protein by means of a

hydrolytically stable amide bond.

If the analyte does not contain a carboxyl group but contains either an amine or thiol, it can be converted to a carboxylic acid derivative as a first step in the synthesis without the necessity of isolating the derivative. Primary and secondary amines react rapidly and quantitatively with succinic anhydride in an appropriate solvent (dimethylforma- mide, dimethylsulfoxide) and the carboxylic acid thus generated can be activated and coupled in the normal manner. An analyte molecule containing a thiol group can be treated with N-succinimidyl bromoacetate and thus converted directly to a derivative in which the carboxyl group is already activated.

If the analyte contains both amine and

carboxylic acid groups, it may be necessary to block the amine to prevent formation of insoluble polymers during activation of the carboxylic acid. For permanent blocking, the acetyl group can be used. If it is necessary that the amine group be free in the final conjugate (to improve the changes of obtaining a specific antibody, for example), block with a trifluoroacetyl group, which can be removed by treating the analyte-protein conjugate with 1 M piperidine or other nucleophilic amine.

There are many CARs commercially available, but 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide

hydrochloride (ECDI) and disuccinimidyl carbonate (DSC) are especially useful. ECDI can be used in either aqueous or organic solvents. Normally, as a first step, one reacts the desired analyte carboxylic acid in either aqueous or organic solvent with ECDI. In water, the maximum rate of reaction occurs at pH 4 to 6; in anhydrous solvents, adjustment of acidity is not necessary because of the acidic nature of both the carboxylic acid and the ECDI hydrochloride. The second step consists of combining the activated acid solution and a solution of the desired amine (or protein) in an appropriate solvent. Reaction of the activated carboxylic acid with the amine is

base-catalyzed:

ECDI reacts with amines very slowly. In some cases reported in the literature, ECDI is simply added to a premixed solution of the carboxylic acid and amine so that activation and coupling take place simultaneously. This should not be done in the synthesis of analyte-protein conjugates because proteins also contain carboxyl groups (aspartate and glutamate), which compete with the analyte carboxylic acid and lead to extensive crosslinking of the protein. A further disadvantage of this procedure arises from the activation step being acid-catalyzed and the subsequent coupling reaction being

base-catalyzed; conditions cannot be optimized for both reactions simultaneously.

An additional disadvantage of ECDI activation is that the activated intermediate, an acylisourea, rearranges to an N-acylurea, which is completely inert (see equations above). To circumvent this problem, a mixture of analyte carboxylic acid, ECDI and N-hydroxysuccinimide (NHS) can be reacted

together so that the acylisourea formed is

immediately converted to the N-succinimidyl ester, which is stable.

DSC is a relatively new reagent that reacts directly with a carboxylic acid to form the

corresponding N-hydroxysuccinimide ester. The reaction proceeds rapidly when catalyzed by tertiary amines (triethylamine, pyridine). Carbon dioxide and N-hydroxysuccinimide are innocuous by-products:

1

DSC is unlike carbodiimides and 2-fluoro-1- methylpyridinium salts in two important aspects. It hydrolyzes rather rapidly, and it reacts very rapidly with primary and secondary amines to form

carbamates. Therefore, activation of the analyte carboxylic acid in an anhydrous, aprotic, water- miscible solvent (dimethylformamide,

dimethylsulfoxide, 1-methyl-2-pyrrolidinone) must be carried out as a separate first step. Unblocked reactive amines should not be present in the analyte.

Bovine serum albumin (BSA) is commonly used as an immunogenic carrier protein and as a protein for the synthesis of coating conjugates. Its molecular weight is 67,000 and it contains 59 available

lysines. Conjugates are prepared by activating an analyte (hapten) carboxylic acid with 1.1 equivalents of DSC in solvent (dimethylformamide,

dimethylsulfoxide, or 1-methyl-2-pyrrolidinone) in the presence of 2 equivalents of triethylamine. The mixture is allowed to react for one hour after addition of the triethylamine. This solution is then mixed with a solution of BSA in buffer, pH 8 to 9. The buffer must not contain amino acids or ammonium salts. The coupling reaction is complete within 3 hours.

Because of such factors as varying DSC quality (resulting in incomplete activation of the hapten carboxylic acid), possible side reactions, and/or competing hydrolysis of the succinimidyl ester formed, quantitative coupling of hapten to protein does not occur.

It is believed that BSA containing an average of 10 to 15 attached haptens will function best as an immunogen. When the number of hapten molecules introduced into a protein or other polyamine is less than the number of amine groups available, the conjugate obtained is a mixture of products of varying degrees of substitution.

Keyhole limpet hemocyanin (KLH) (Sigma Chemical Co., St. Louis, MO) is about 90% soluble in 0.15 M sodium bicarbonate at pH 8.1 and nearly completely soluble in 0.15 M HCO₃-/CO₃ ⁼ buffer at pH 10. Any insoluble material should be removed by

centrifugation before addition of the activated hapten.

KLH is believed to contain about 20 reactive lysines per 100 kD. In immunogen synthesis with activated hapten carboxylic acids, use at least 60 moles of activated hapten per 100 kD of KLH. The conjugate solutions are generally dialyzed first against several changes of 0.15 M sodium bicarbonate, then against either phosphate buffer or, if the conjugate is to be lyophilized, against deionized water. The conjugate remains soluble in spite of the changes in pH and ionic strength. Once lyophilized, however, the conjugate is difficult to dissolve again. Dissolution is aided by moistening the dry conjugate with a few μL of ethanol -- this expels air and facilitates wetting -- and using a buffer with as high a pH as possible.

Pumpkin seed globulin (PSG) and marijuana seed globulin (edestin) are available from Sigma. They are inexpensive and function well as carrier proteins for immunogen synthesis. By definition, globulins are proteins that are not soluble in pure water or weak salt solutions but are soluble in fairly

concentrated salt solutions. PSG is particularly useful and is completely soluble in buffers

containing at least 0.5 M NaCl. Our sample consists of a major component eluting in the 150,000 MW range on a GF 450a column, and a minor component eluting in the 500,000 MW range. It is estimated that PSG contains about 20 reactive lysines per 100 kD, the same as KLH.

Although native PSG is completely soluble in high-salt buffers, it becomes insoluble when the amine groups are conjugated. Precipitation of conjugate begins shortly after the activated hapten carboxylic acid is mixed with the PSG solution and continues during dialysis against low-salt buffers and distilled water. The conjugate has generally been isolated by lyophilization of the suspension, but simple centrifugation might also be satisfactory.

The commercial samples of edestin that were used were only about 50% soluble in salt solutions. Edestin is probably isolated from marijuana seeds that have been heated to destroy viability, which process can severely denature the protein.

Nevertheless, the soluble portion of edestin may be satisfactory for immunogen synthesis. Conjugates are insoluble.

Proteins for Coating Conjugate Synthesis

As used here, the term "coating conjugate" signifies a reagent used to bind antianalyte antibody from sera or other liquid medium to a solid support. The first step in this operation is attachment of the coating conjugate itself to the support. Attachment may be through physical adsorption (on polystyrene, for example) or by chemical bonding through

appropriate functional groups on both the conjugate and the support. If the coating conjugate is to be adsorbed to polystyrene, a protein known to adsorb tenaciously and resist displacement by detergent and other proteins should be chosen for synthesis of the conjugate. If the coating conjugate is to be

chemically bonded to the support (this is typically done through residual lysine groups), the protein chosen must have a sufficient number of lysines to allow both the initial attachment of an adequate number of analyte hapten molecules and the subsequent attachment of the resulting conjugate to a

functionalized support.

It is sometimes possible to use the same conjugate as both an immunogen and a coating

antigen. However, this approach is not generally used for screening sera for the presence of

antianalyte antibodies since it would pick up

concomitant antibodies against various peptide segments in the carrier protein and greatly increase the number of false positives.

Bovine serum albumin (BSA) and ovalbumin are proteins especially preferred for synthesis of coating conjugates. Conjugates remain soluble, even when a substantial fraction of the available lysine groups have been coupled to hydrophobic haptens, and are suitable for attachment to supports by either adsorption or by chemical bonding through residual lysines. After adsorption of the coating conjugate to polystyrene, it is generally necessary to block the plate with another protein such as BSA or milk protein (casein), or polyvinylpyrrolidone, to prevent subsequent adsorption of nonspecific antibodies.

Synthesis of Antigen-Protein Conjugates

The pK_a of a peptidic lysine residue is 10.5. Theoretically, this is the pH at which the

concentrations of protonated and unprotonated amine groups are equal, or, better, the pH at which any given amine group is unprotonated 50% of the time. Since it is the unprotonated amine that reacts with an activated carboxylic acid, it is advantageous to carry out conjugations in basic solution.

Bicarbonate/carbonate buffer systems have proved satisfactory. In any case, the system must not contain amino acids, ammonium salts or any reactive primary or secondary amine other than that present on the protein being conjugated.

Special care should be taken to protect

carboxyl-activating reagents [1-(3-dimethylamino- propyl)-3-ethylcarbodiimide hydrochloride (ECDI) and disuccinimidyl carbonate (DSC) from atmospheric moisture. Purchase small quantities and store the bottles in the refrigerator in a plastic jar

containing a calcium carbonate drying agent. Two or three hours before a sample is needed, remove the jar from the refrigerator and allow it to warm to room temperature before opening. Open the jar, then the bottle, and quickly transfer somewhat more material than will be needed to another container.

Immediately close the bottle and return it to the jar and to the refrigerator. New bottles should be dated when opened; discard unused material 3 months after opening.

EXAMPLE 1

Synthesis of Compound 11-KLH Conjugate

The depicted Compound 11 was selected for use in the coating conjugate used to detect the sulfonylurea, bensulfuron methyl. However, the conjugation procedure described here is a model for synthesis of conjugate from any analyte carboxylic acid that is soluble in and not affected by either DMF, DMSO,

1-methylpyrrolidinone, or other water-miscible, inert solvent. In this Example, DMF is used as a solvent in the activation step because sulfonylureas are known to slowly degrade in DMSO when exposed to light. The conjugation is carried out at pH 8 to avoid hydrolysis of the methyl ester group present in Compound 11. If the desired analyte carboxylic acid lacks base-sensitive groups, it is advantageous to use higher pH to improve the solubility of KLH. The molecular weight of KLH is very high. For this reason, it dissolves very slowly, even in alkaline buffers.

Stoichiometry: 60 moles of Compound 11 per 100 kD of KLH. (For purposes of calculation, assume that the KLH is 100% pure and completely soluble).

DSC/Compound 13 mole ratio = 1.10.

KLH Solution: KLH (Sigma) [150 mg] was weighed into a 40 mL, polycarbonate centrifuge tube. A magnetic stirring bar was added and 15.0 mL of 0.15 M sodium bicarbonate was added (pH = 8.1). The mixture was stirred for about one hour at room temperature, then an additional 10.0 mL of 0.15 M sodium bicarbonate was added. The mixture was stirred at room

temperature for 3 more hours. The sample was stored in a refrigerator overnight and then removed from the refrigerator and stirred an additional hour the next day. The magnetic stirrer bar was withdrawn and the sample centrifuged. The supernatant liquid was stored in a 2-ounce bottle in the refrigerator for later use in conjugate synthesis.

DSC Stock Solution: This solution is made up

immediately before use, that is, after Compound 11 has been weighed out (below). The values indicated here for DSC and total weight of solution are guides. It is not necessary to get these exact values. Actual values should be recorded to the precision indicated.

An amount of 51.00 mg of disuccinimidyl

carbonate (DSC; MW = 256.2) was weighed directly into a 4 mL, screw-capped vial. Dry DMF was added to bring the total weight to 3.400 grams, was agitated in the vial until the DSC had completely dissolved. The density of the solution was detected by weighing a 1000 μL sample (discard this sample). A typical value is 0.9589 g/mL. From the actual weights

obtained, the concentration of DSC in mmoles/μL was calculated:

DSC cone. = = 5.614 x 10^-5 mmoles/μL.

An amount of 40.90 mg (9.000 x 10^-2 mmoles) of Compound 11 was weighed directly into a 4 mL,

screw-capped, vial. A magnetic stirrer bar was added, and 9.900 x 10^-2 mmoles of DSC were added

(1763 μL). The mixture was stirred until the

Compound 11 had dissolved. 20 μL of triethylamine was added, and stirring continued at room temperature for exactly one hour.

At the end of the one-hour activation period, the activated Compound 11 solution was quickly

transferred to the rapidly-stirred KLH solution. The solution was transferred back and forth between the two containers to effect quantitative mixing. (No precipitate should form during this step.) The sample was stored in the refrigerator overnight. The sample was dialyzed against 3 changes of 0.15 M sodium bicarbonate (2 liters each), then, (a) if the conjugate is to be lyophilized, against 3 changes of deionized water, or (b) if the conjugate is to be aliquoted and stored frozen, against 3 changes of phosphate buffer. The average yield of lyophilized conjugate is 120 to 130 mg. If the dialyzed

conjugate is not lyophilized, the approximate

conjugate concentration can be obtained by dividing 125 mg by the final volume of the dialyzate.

EXAMPLE 2

Synthesis of Compound 9-BSA Conj ugate

The secondary amine present in this molecule is so weakly nucleophilic that it is not considered necessary to block it. The conjugate is intended for use as an immunogen. The object is to attach 10 to 15 molecules of the Compound 9 to each BSA molecule.

Stoichiometry: Compound 9/BSA mole ratio = 30; DSC/Compound 9 ratio = 1.1. BSA Solution: Dissolve 100 mg of BSA in 10.0 mL of 0.15 M sodium bicarbonate, pH 8.1.

Compound 9 (20.78 mg; 4.753 x 10^-2 mmoles) was weighed directly into a 1 mL reaction vial. A magnetic stirring bar was added and an amount of DSC stock solution was pipetted in that contains 5.503 x 10^-2 mmoles of DSC, here, (5.503 x 10^-2)/(5.614 x 10^-5) = 896 μL. The mixture was stirred until the Compound 11 had dissolved; 10 μL of triethylamine was added, and stirring continued at room temperature for exactly one hour.

At the end of the one-hour activation period, the activated Compound 9 solution was quickly

transferred to the rapidly-stirred BSA solution. The solution was transferred back and forth between the two containers to effect quantitative mixing. (No precipitate should form during this step.) The sample was stored in the refrigerator overnight. The sample was dialyzed against 3 changes of 0.15 M sodium bicarbonate, then against 3 changes of

phosphate buffer (2 liters each change). The

conjugate concentration was estimated by dividing 90 mg by the final volume of dialyzate (that is, assume that 10% of the protein is lost during the synthesis process). The solution was aliquoted into suitable sample sizes and stored frozen until ready to

immunize. EXAMPLE 3

Synthesis of Compound 1-OVA Conjugate

This conjugate is intended for use as a coating antigen. The object is to attach 7 to 10 molecules of the Compound 1 to each ovalbumin molecule.

Stoichiometry: Compound 1/ovalbumin mole ratio = 20; DSC/Compound 1 ratio = 1.1.

Ovalbumin Solution: Dissolve 100 mg of ovalbumin in 10.0 mL of 0.15 M sodium bicarbonate, pH 8.1.

An amount of 20.78 mg (4.446 x 10^-2 mmoles) of Compound 1 was weighed directly into a 1 mL reaction vial. A magnetic stirring bar was added and that amount of DSC stock solution was pipetted that contains 4.891 x 10^-2 mmoles of DSC, here, (4.891 x 10^-2)/(5.614 x 10^-5) = 871 μL. The mixture was stirred until the Compound 1 had dissolved. 10 μL of triethylamine was added, and stirring continued at room temperature for exactly one hour. At the end of the one-hour activation period, the activated Compound 1 solution was quickly transferred to the rapidly-stirred ovalbumin

solution. The solution was transferred back and forth between the two containers to effect

quantitative mixing. (No precipitate should form during this step.) The sample was stored in the refrigerator overnight. The sample was dialyzed against 3 changes of 0.15 M sodium bicarbonate, then against 3 changes of phosphate buffer (2 liters each change). The conjugate concentration was estimated by dividing 90 mg by the final volume of dialyzate (that is, assume that 10% of the protein is lost during the synthesis process). Antimicrobial agents were added to the solution before storage.

Using the procedure described above, the following sulfonylureas were conjugated with the following proteins, and purified by dialysis.

a. Made as described in Example 3. ANTIBODY PRODUCTION

Vallejo et al., J. Agric. Food Chem., 30, (1982), pages 572 to 580 studied different hapten structures for parathion. He concluded that "the determinant groups of the small molecule must be preserved" and that "the hapten's determinant groups must not be masked" for antibody production. One format used for pesticide immunoassays has utilized a solid phase with hapten bound to it (coating

conjugate) for capture of antibodies not bound to free compound. The quantification of the captured antibody is used to determine the original

concentration of compound in the original aqueous sample.

Hapten structures were further explored by Wie et al., J. Agric. Food Chem., 32 , (1984), pages 1294 to 1301 to develop an assay for diflubenzuron. Their main purpose was to show that sensitive assays could be achieved by using a coating antigen of different structure than the immunizing hapten.

Thus, they demonstrated that some sensitivity could be formed by shifting linker arm position, and that lack of specificity could be achieved by changing functional groups.

Van Emon et al.. Analytical Methods for

Pesticides and Plant Growth Regulators, Vol. XVII, (1989), pages 217 to 263 state that "the point of attachment of hapten to protein should occur away from any suspected antigenic determinants" to insure proper antigenic response for developing specific antibodies. They also state that to develop a compound class specific assay the hapten structure for immunization is important, particularly

preserving the common antigenic determinants of the related compounds. EXAMPLE 4 Rabbit Immunization Protocol for Compound 3

Three New Zealand white rabbits were immunized with a conjugate prepared by coupling the Compound 3 to keyhole limpet hemocyanin (KLH) using the schedule set out in Table 9. Where the use of an adjuvant is indicated, 0.5 mL of the adjuvant was mixed with 0.5 mL of a solution or suspension of the conjugate in phosphate buffered saline to form an emulsion.

1. subcutaneously

2. complete Freund's adjuvant

3. intramuscularly

4. incomplete Freund's adjuvant

5. intravenously

Antiserum was collected on the seventh, ninth and twelfth days following each boost from days 350 to 470.

EXAMPLE 5 Rabbit Immunization Protocol for Compound 4

Three New Zealand white rabbits were immunized with a conjugate prepared by coupling the Compound 4 to KLH using the schedule set out in Tables 10a and b. Where the use of an adjuvant is indicated, 0.5 mL of the adjuvant was mixed with 0.5 mL of a solution or suspension of the conjugate in phosphate buffered saline to form an emulsion.

Antiserum was collected twenty days after the boost on day 66 and on the fourteenth day following each boost from days 220 to 440.

Antiserum was collected on the fourteenth day following each boost from days 220 to 440. EXAMPLE 6 Rabbit Immunization Protocol for Compound 9

Three New Zealand white rabbits were immunized with a conjugate prepared by coupling the Compound 9 to KLH using the schedule set out in Table 11. Where the use of an adjuvant is indicated, 0.5 mL of the adjuvant was mixed with 0.5 mL of a solution or suspension of the conjugate in phosphate buffered saline to form an emulsion.

Antiserum was collected on the fourteenth day following each boost from day 44 to day 164 and on the seventh, ninth and eleventh days following each boost from days 210 to 420.

Using the method described in Examples 4 to 6, antisera to the following conjugates were produced:

Example No. Conjugate

7 Compound 8 - BSA

8 Compound 8 - KLH

9 Compound 12 - KLH

METHOD OF MEASURING SULFONYLUREA CONCENTRATIONS

GENERAL PROCEDURE

Optimization of First Antibody Titer and Coating

Conjugate Concentration

Optimum starting concentrations for the reagents in this immunoassay are determined with a checkerboard assay. In this assay, decreasing concentrations of coating antigen are coated on a plate in one direction, for instance 10 μg/mL across the first row, 1 μg/mL across the second row, and on down. Increasing dilutions of antisera are added to the plate in the other direction, for instance a dilution of 100 down the first column of wells, 1000 down the second column, etc. In this manner, the binding of each concentration of antisera to each concentration of coating antigen is determined at a fixed time point. The combination of antisera and coating conjugate concentrations giving a half-maximal (O.D. = 1.0) reading after addition of second antibody and substrate is optimum. Two or three combinations can be chosen for the next step, generation of an inhibition curve.

The optimum concentration of the antisera of Example 8 and coating conjugate ovalbumin-Compound 8 was determined with this checkerboard assay as described next. Coating conjugate solution was made consisting of the conjugate dissolved in Coating buffer at 10, 1 and 0.1 and 0.01 μg/mL

concentrations. The coating antigen solutions (200 μL) were pipetted into polypropylene microtiter wells such that each concentration ran across the plate in a row with decreasing concentrations from top to bottom. Peripheral wells were not used because of the occasional variability of results.

The plates were incubated at 4°C for 16 hours, and dried. Plates were washed with IX PBS-Tween^® (PBST) three times in a plate washer and dried by hitting the plate 3-4 times upside-down against a paper towel to remove water droplets from the sides of the wells. Aliquots (200 μL) of serial two-fold dilutions of antisera in IX PBST with 0.5% BSA and

0.1% gelatin starting at a dilution of 200 and ending at 204,800, were added to wells from left to right across the plate. Plates were incubated 1.5 hours at room temperature and then washed again with IX PBST as described above. Goat anti-rabbit IgG antibody labeled with alkaline phosphatase was dissolved in IX PBST with 0.5% BSA and 0.1% gelatin at a dilution of 1:5000 and 200 μL was added to each well. Plates were incubated at room temperature for one hour.

After washing the plates, the para-nitrophenyl phosphate substrate was dissolved (1 mg/mL) in substrate buffer and 200 μL was added to the

microtiter wells. The plates were incubated at room temperature for a total of 40 minutes and read at 405 nm. Optimal titer and coating antigen concentrations were determined by those concentrations reaching an absorbance of 1.0 O.D. units after 20 minutes

incubation and corresponding to 50% inhibition of the enzyme reaction.

The optimum antiserum dilution was determined to be 1:25,000; and the optimum coating conjugate concentration was determined to be 0.1 μg/mL. Standard Preparation:

Chlorsulfuron, 99.7% pure analytical standard (E. I. du Pont de Nemours and Co., Inc., Agricultural Products Department, Wilmington, Delaware, 19880) was used to make up the standard curve. 10 mg of

chlorsulfuron was weighed and placed into a 100-mL volumetric flask, then dissolved in 100 mL methylene chloride. This standard is stable for several months in the refrigerator and is used to make all working standards during the procedure.

Standard Curve Preparation:

An amount of 50 μL of the 100 μg/mL standard from above was transferred into the bottom of a 15 x 85 mm culture tube and air dried 5 to 10 minutes until all the solvent was evaporated. 5 mL of 1x

PBS/Protein was added, covered with paraffin film and vortexed vigorously. It was reconstituted at least 1/2 hour with occasional vortexing. Standard gave the following concentrations: 100 ng/mL, 12.5 ng/mL, 3.1 ng/mL, 0.8 ng/mL, 0.2 ng/mL, 0.05 ng/mL, 0.01 ng/mL, 0.003 ng/mL and 0.0008 ng/mL. A final volume of 1.8 mL of each was added to a small 15 x 85 mm glass disposable culture tube. 0.2 mL of 10x PBS/Protein (0.5% BSA, 0.1% gelatin) was added to the tube for a final volume of 2.0 mL.

Fresh 1:500 dilution antisera stock was made by adding anti-chlorsulfuron antisera #127 from Example 8 and PBS/Protein. 20 μL of the 1:500 titer antisera was added to all tubes except the reagent blank. It is most important that the antisera stock not touch the glass before the solution to ensure reproducible amounts of antisera entering each tube. The tubes were gently vortexed, covered with a strip of

paraffin film making sure each tube was sealed against the film, and incubated overnight on the bench at room temperature.

(i) Plate Preparation: Coating conjugate was made up by adding 12.5 μl of the 0.1 μg/mL Compound 8-OVA per 25 mL PBS/Protein. Using a 12-channel pipetter, 200 μL was added to every well of a

microtiter plate, covered, sealed in a plastic bag and incubated 4°C overnight. Blocking was done the next day. The coated plates were washed three times with lx PBST and dried. To block the plates, 200 μL of 3% BSA was added to each well with a 12-channel pipetter. The plates were incubated 2 hours at room temperature.

(ii) Tube Addition: The plate was washed and dried by the same procedure as described above. 200 μL was added to three wells for each standard sample tube with a repeater pipette. For each tube 0.2 mL was added into four wells, tips changed and another tube added to another four wells. Care was taken to prevent splashing of contents from the wells. The plate was incubated at room temperature 1 hour.

(iii) Second Antibody Addition: The plates were washed and dried. Fresh second antibody was prepared as described above. Then 200 μL per well was added to the plate. The plate was allowed to incubate 1 hour at room temperature.

(iv) Enzyme Substrate Addition: The plate was washed and dried, and 200 μL of 1 mg/mL substrate solution was added to each well. The plate was incubated at room temperature and read. The plate was read between 1.0 to 2.0 O.D. If stopping the reaction was necessary, 50 μL of stop solution (10N NaOH) was added to each well.

Using the above procedure, the following measurements were made:

(a) The detection limit is the minimum concentration of pesticide needed to produce 15% inhibition of absorbance relative to negative control. The assay can be applied to any aqueous water sample including aqueous soil extract. Two examples follow.

EXAMPLE 15

LAKE WATER

A standard curve was generated as described in Procedure I. Triplicate 1.8 mL aliquots of lake water were placed in the 15 x 85 mm disposable culture tubes. Then, 0.2 mL 10X PBS/Protein was added as described above followed by 20 μL of 500 titer antisera stock as described. The assay steps were followed exactly as described in sections

(i)-(iv) and the Flow Laboratories Titercalc software using a four parameter logistic calculated the concentration of chlorsulfuron in the water samples versus the standard curve. A detection limit of 10 pg/mL was obtained, wherein the detection limit is as defined with respect to Examples 10 to 14.

EXAMPLE 16

SOIL SAMPLES

Ten grams of soil were extracted with 20 mL of 0.2 M ammonium bicarbonate buffer using either a probe sonicator at low wattage for 3 minutes or overnight tumbling. The slurry was centrifuged at 5,000 g for 15 minutes to pellet the solids.

Aliquots of 1.8 mL volume of the supernatant are used directly in the assay. The standard curve was generated as described above except that extract from untreated soil was used instead of water. Sample aliquots from treated soil of 1.8 mL volume were taken in duplicate and run against the standard curve. A 25 pg/mL detection limit was attainable in the soil extract.

Claims

CLAIMS What is claimed is:

1. A compound having the formula

wherein J is

G is H or MO₂C(alkyl)_nL;

n is 0 or 1;

alkyl is 1 to 3 carbon atoms optionally

substituted with one or two of halogen, methyl, methoxy, or methylthio;

L is O, S, NR⁵, -N(C=O)- or a direct bond;

R, R⁴ and R⁵ are independently H or CH₃;

E is a single bond or CH₂;

alkylsulfinyl, C₁ to C₃ alkylsulfonyl,

CH₂CN, CN, CO₂R^c, C₁ to C₃ haloalkoxy, C₁ to

C₃ haloalkylthio, C₂ to C₄ alkoxyalkyl, C₃ to C₄ alkoxyalkoxy, C₂ to C₄ alkylthioalkyl, CH₂N₃, NR^dR^e, or Q;

R^a is H, C₁ to C₄ alkyl, C₂ to C₃ cyanoalkyl, methoxy or ethoxy;

R^b is H, C₁ to C₄ alkyl or C3 to C₄ alkenyl; or R^a and R^b may be taken together as -(CH₂)₃-,

-(CH₂)₄-, -(CH₂)₅- or -CH₂CH₂OCH₂CH₂-;

R^c is _C1 to C₄ alkyl, C₃ to C₄ alkenyl, C₃ to C₄ alkynyl, C₂ to C₄ haloalkyl, C₂ to C₃ cyanoalkyl, C₅ to C₆ cycloalkyl, C₄ to C₇ cycloalkylalkyl or C₂ to C₄ alkoxyalkyl;

containing one heteroatom selected from O, S, or N, tetrazole optionally substituted with C₁-C₃ alkyl, or an unsaturated 5- or 6-membered ring containing 1 to 3

heteroatoms selected from 0-1 S, 0-1 O or

0-3 N and when Q is an unsaturated 5- or 6-membered ring, it may optionally be substituted by one or more groups selected from C₁ to C₄ alkyl, halogen, C₃ to C₄ alkenyl, C₁ to C₃ alkoxy, C₁ to C₃

X is H, C₁ to C₄ alkyl, C₁ to C₄ alkoxy,

C₁ to C₄ haloalkoxy, C₁ to C₄ haloalkyl, halogen, C₂ to C₅ alkoxyalkyl, C₂ to C₅ alkoxyalkoxy, amino, C₁ to C₃ alkylamino, di(C₁ to C₃ alkyl)amino or C₃ to C₅

Y is H, C₁ to C₄ alkyl, C₁ to C₄ alkoxy, C₁ to C₄ haloalkoxy, C₂ to C₅ alkoxyalkyl, C₂ to C₅ alkoxyalkoxy, amino, C₁ to C₃ alkylamino, di(C₁ to C₃ alkyl) amino, or C₁ to C₄ alkyl; M is H or an alkali or alkaline earth metal salt;

R³ is H or C₁ to C₃ alkyl;

Z is CH, N or CCO₂M; and

E¹ is a direct bond or CH₂; wherein

(i) when G is not H and when L is a direct bond, then n = 1;

(ϋ) when G is H, then J is J-1, J-4 or J-5;

(v) when J is J-1, G is 3-CO₂H, X is CH₃ and Y is OCH₃, then Z is not N.

2. A sulfonylurea-protein conjugate

comprising a sulfonylurea of the formula

wherein J is

G is H or MO₂C(alkyl)_nL; or

n is 0 or 1;

alkyl is 1 to 3 carbon atoms optionally substituted with one or two of halogen, methyl, methoxy, or methylthio;

L is O, S, NR⁵, -N(C=O)- or a direct bond;

R, R⁴ and R⁵ are independently H or CH₃;

E is a single bond or CH₂; R¹ is H, C₁ to C₃ alkyl, C₁ to C₃ haloalkyl, halogen, nitro, C₁ to C₃ alkoxy, SO₂NR^aR^b, CONR^aR^b, C₁ to C₃ alkylthio, C₁ to C₃

alkylsulfinyl, C₁ to C₃ alkylsulfonyl,

CH₂CN, CN, CO₂R_c, C₁ to C₃ haloalkoxy, C₁ to C₃ haloalkylthio, C₂ to C₄ alkoxyalkyl, C₃ to C₄ alkoxyalkoxy, C₂ to C₄ alkylthioalkyl, CH₂N₃, NR^dR^e, or Q;

R^a is H, C₁ to C₄ alkyl, C₂ to C₃ cyanoalkyl, methoxy or ethoxy;

R^b is H, C₁ to C₄ alkyl or C₃ to C₄ alkenyl; or R^a and R^b may be taken together as -(CH₂)₃-, -(CH₂)₄-, -(CH₂)₅- or -CH₂CH₂OCH₂CH₂-;

R^c is C₁ to C₄ alkyl, C₃ to C₄ alkenyl, C₃ to C₄ alkynyl, C₂ to C₄ haloalkyl, C₂ to C₃ cyanoalkyl, C₅ to C ₆ cycloalkyl, C₄ to C₇ cycloalkylalkyl or C₂ to C₄ alkoxyalkyl;

heteroatoms selected from 0-1 S, 0-1 O or

0-3 N and when Q is an unsaturated 5- or 6-membered ring, it may optionally be

substituted by one or more groups selected from C₁ to C₄ alkyl, halogen, C₃ to C₄ alkenyl, C₁ to C₃ alkoxy, C₁ to C₃ alkylthio, C₃ to C₄ alkenylthio, C₁ to C₂ haloalkoxy or C₁ to C₃ haloalkylthio;

X is H, C₁ to C₄ alkyl, C₁ to C₄ alkoxy,

C₁ to C₄ haloalkoxy, C₁ to C₄ haloalkyl, halogen, C₂ to C₅ alkoxyalkyl, C₂ to C₅ alkoxyalkoxy, amino, C₁ to C₃ alkylamino, di(C₁ to C₃ alkyl) amino or C₃ to C₅ cycloalkyl; or C₁ to C₄ alkyl, C₁ to C₄ alkoxy or C₁ to C₄ haloalkoxy substituted on the alkyl, alkoxy or haloalkoxy group with CO₂M;

Y is H, C₁ to C₄ alkyl, C₁ to C₄ alkoxy, C₁ to C₄ haloalkoxy, C₂ to C₅ alkoxyalkyl, C₂ to C₅ alkoxyalkoxy, amino, C₁ to C₃ alkylamino, di(C₁ to C₃ alkyl) amino, or C₁ to C₄ alkyl; M is H or an alkali or alkaline earth metal

salt;

R³ is H or C₁ to C₃ alkyl;

Z is CH, N or CCO₂M; and

E¹ is a direct bond or CH₂; and a protein.

3. A conjugate according to Claim 2 wherein the protein is selected from the group pumpkin seed globulin, keyhole limpet hemocyanin, marijuana seed globulin, ovalbumin and bovine serum albumin.

4. A conjugate according to Claim 3 wherein the compound is selected from the group of compounds (1) through (12) and the protein is selected from the group pumpkin seed globulin, keyhole limpet

hemocyanin, ovalbumin and bovine serum albumin.

5. A conjugate according to Claim 4 wherein the compound is selected from the group of compounds (2), (3), (4), (8), (9) and (12) and the protein is keyhole limpet hemocyanin.

6. A conjugate according to Claim 4 wherein the compound is selected from (8) and (9) and the protein is bovine serum albumin.

7. A conjugate according to Claim 4 wherein the compound is selected from (8) and (12) and the protein is ovalbumin.

8. A conjugate according to Claim 4 wherein the compound is compound (8) and the protein is pumpkin seed globulin.

9. Antibodies to the conjugate of any one of Claims 2 through 8.

10. Antibodies to the conjugate of any one of Claims 2 through 8 produced in rabbits.

11. An improved enzyme-linked immunosorbent assay for detecting the presence of a sulfonylurea in an unknown sample comprising the steps: (A) forming a complex of the sulfonylurea with an excess of a first antibody of known concentration,

(B) complexing the unbound first antibody from Step A with a coating conjugate adhered to a solid phase,

(C) binding a labeled antibody to the

antibody-conjugate complex of B, and

(D) determining the presence and the amount of sulfonylurea in the unknown sample by measuring the amount of unbound antibody in Step A with reference to controls which comprise known concentrations of the sulfonylurea;

wherein the improvement comprises (i) employing a conjugate according to Claim 2 as an immunogen to generate the antibody in Step A; and (ii) employing the same or a different conjugate according to

Claim 2 as coating conjugate in Step B.

12. An assay according to Claim 11 employing a compound selected from the group of compounds (1) to (12) conjugated with a protein selected from heyhole limpet hemocyanin, pumpkin seed globulin, marijuana seed globulin, ovalbumin and bovine serum albumin.

13. An assay according to Claim 11 wherein the antibody employed in Step A is produced in a rabbit.

14. An assay according to Claim 12 employing a compound selected from at least one member of the group (1), (2), (3), (4), (8) and (12) conjugated with a protein selected from at least one member of the group pumpkin seed globulin, keyhole limpet hemocyanin, ovalbumin and bovine serum albumin.

15. An assay according to Claim 11 for measuring the presence of a sulfonylurea selected from the group chlorsulfuron, metsulfuron methyl, chlorimuron ethyl and bensulfuron methyl.

16. An assay according to Claim 14 wherein the antibody employed in Step A is produced in a rabbit.

17. A kit useful for measuring the presence of a target sulfonylurea in an unknown sample

comprising the components:

(i) an antibody to the sulfonylurea in the unknown;

(ii) a solid phase having a coating conjugate bound to it;

(iii) a labeled antibody that recognizes antibody (i);

(iv) a developer that develops color in the presence of a label; and

18. A test kit according to Claim 17

comprising an antibody to a target sulfonylurea selected from the group chlorsulfuron, bensulfuron methyl, metsulfuron methyl and chlorimuron ethyl.

19. A method for using the kit according to Claim 17 or Claim 18 to detect a target sulfonylurea comprising contacting components i, ii, iii and iv and comparing the color that is developed to

controls, v, thereby determining the presence and concentration of the target sulfonylurea.

20. A compound according to Claim 1 wherein J is J-1, J-2, J-3 or J-4; E¹ is a direct bond and Y is methoxy, ethoxy, methyl, methylamino or chloro.