Preparation of New Haptens for Use in Immunoassay of Glycine-Conjugated Bile Acids

The N-succinimidyl esters of various glycine-conjugated bile acid 3-hemisuccinates and 3-hemiglutarates have been prepared for use in immunoassay. Unconjugated bile acids were condensed with p-nitrophenol to form the activated esters. Subsequent reaction with 2,2,2-trichloroethyl glycinate provided the glycine-conjugated trichloroethyl esters. On treatment with succinic anhydride and glutaric anhydride in pyridine, the glycine-conjugated bile acids were led to the 3-hemisuccinates and 3-hemiglutarates, respectively. Condensation of these half esters with N-hydroxysuccinimide was effected by the use of water-soluble carbodiimide to provide the N-succinimidyl esters. Elimination of the protecting group in the side chain was achieved by reduction with zinc dust in tetrahydrofuran-potassium dihydrogen phosphate solution, yielding the desired haptens.