Thiazolidine-2,4-dicarboxylic acid and its esters: Synthesis, in solution behaviour and regioselective cyclocondesation

Article abstract of DOI:10.1002/jhet.5570310114

Thiazolidine-2,4-dicarboxylic acid 2 was obtained as a diastereoisomeric mixture from the condensation of glyoxylic acid with L(-)R-cysteine Σ. In solution behaviour studies suggested that the reaction proceeded through an acid catalyzed epimerization mechanism. The methyl esterification of 2 was stereoselective, which can be explained by an interconversion of 2a via a ring seco intermediate. Condensation of the dimethyl 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 bicyclic derivatives 3-10.