SYNTHESIS AND STEREOCHEMICAL STUDIES OF 6-SUBSTITUTED -3,3-DIMETHYLIMIDAZO[1,5-C]THIAZOL-5-ONE-7-THIONES

The reaction of (4S)-5,5-dimethyl-4-thiazolidine-carboxylic acid 1 wit h alkyl and aryl isothiocyanates 2 gave bicyclic thiohydantoins 3. The (2R,4S)- and (2S,4S)-mixtures of 2-substituted 5,5-dimethyl-4-thiazol idine-carboxylic acids 4 and 8 containing two centers of chirality in the analogous reaction afforded thiohydantoins 7 and 10, respectively, with (1R)-configuration. In some cases we managed to isolate the thio ureido acid intermediates 6 and 9 or their triethylamine salts which a fforded the corresponding bicycles 7 and 10 under thermal cyclization or acidification. The stereochemistry has been elucidated by high reso lution nmr studies, optical rotation measurements and X-ray crystallog raphy.