Syntheses of 15 alpha- and 15 beta-carboxymethyltestosterone bovine serum albumin conjugates: characteristics of the antisera to testosterone.

Syntheses of 15 alpha- and 15 beta-carboxymethyltestosterone (15 alpha- and 15 beta-CMT) were investigated in order to prepare testosterone-bovine serum albumin conjugates for radioimmunoassays of testosterone. A mixture of 15 alpha- and 15 beta-bis(ethoxycarbonyl)methyl-3 beta-hydroxy-5-androsten-17-one (IIa and IIb) obtained by a reaction of 3 beta-hydroxy-5,15-androstadien-17-one (I) and sodium diethyl malonate was oxidized to afford a mixture of 15 alpha- and 15 beta-bis(ethoxycarbonyl)methyl-4-androstene-3, 17-dione (Va and Vb). After the separation by silica gel chromatography, each epimer obtained was hydrolyzed by acid, followed by decarboxylation, and selective reduction of the 17-ketone to give 15 alpha- and 15 beta-CMT. The antisera, generated in rabbits by immunization with the bovine serum albumin (BSA) conjugates of 15 alpha- and 15 beta-CMT, respectively, exhibited high specificity for testosterone.