SYNTHESIS OF 17-BETA-HYDROXY ESTERS OF 4-ESTREN-17-BETA-OL-3-ONE AND CARBENICILLIN, TICARCILLIN, OR FUNCTIONALIZED OXACILLIN - POTENTIALLY USEFUL CONJUGATES FOR BETA-LACTAMASE-BASED HOMOGENEOUS IMMUNOASSAYS

On the basis of the large range of kinetic constants of their substrat es, beta-lactamases seem to be interesting enzymes for the development of homogeneous immunoassays. For this purpose, hapten-penicillin or - cephalosporin conjugates have to be prepared. The aim of this work is to couple the anabolizing steroid nandrolone to several penicillins ch aracterized by extremely low K-m and k(cat) values: ticarcillin, carbe nicillin, and oxacillin. The easy decarboxylation of derivatives of ph enylmalonic acid (carbenicillin) and thienylmalonic acid (ticarcillin) imposes the choice of very mild procedures which have been specifical ly adapted to each substance investigated. 4-Estren-17 beta-ol-3-one h emiphenylmalonate is conjugated to 6-aminopenicillanic acid after 1,1' -carbonyldiimidazole activation, while 4-estren-17 beta-ol-3-one hemi( 3-thiophene)malonate is coupled to 6-aminopenicillanic acid after acti vation using methanesulfonyl chloride. Before conjugation of oxacillin , a carboxylated analogue of its side chain has been prepared. A proce dure resorting to tert-butyl ester protection of the carboxyl group pr esent on the isoxazole ring allows the binding of nandrolone to the re maining carboxyl followed, after specific deprotection, by the conjuga tion to 6-aminopenicillanic acid giving the oxacillin derivative. In t his way, conjugates retaining immunological properties of nandrolone a nd high inhibiting power of beta-lactamases should be obtained.