THIAZOLIDINE-2,4-DICARBOXYLIC ACID AND ITS ESTERS - SYNTHESIS, IN SOLUTION BEHAVIOR AND REGIOSELECTIVE CYCLOCONDENSATION

Thiazolidine-2,4-dicarboxylic a,id 2 was obtained as a diastereoisomer ic mixture from the condensation of glyoxylic acid with L(-)R-cysteine 1. In solution behaviour studies suggested that the reaction proceede d through an acid catalyzed epimerization mechanism. The methyl esteri fication of 2 was stereoselective, which can be explained by an interc onversion of 2a via a ring seco intermediate. Condensation of the dime thyl ester 3 or the dissymmetric diester 4 with phenyl isocyanate gave rise to the same hydantoin 5. N-acylation of diesters 3 or 4 followed by the reaction with benzylamine was regioselective leading to bicycl ic derivatives 8-10.