HETEROCYCLIC-COMPOUNDS FROM SUGARS .15. O N THE CONFIGURATION OF CHIRAL C-2 SUBSTITUTED 1,3-THIAZOLIDINE-4-CARBOXYLIC ACIDS - CHIRALITY TRANSFER TO C-3 OF 3,4-DIHYDRO-1H-PYRROLO[1,2-C]THIAZOLES

5-Substituted ,4-dihydro-pyrrolo[1,2-c]thiazole-6,7-dicarboxylic acid esters 3 are obtained from 2-substituted-3-acyl-1,3-thiazolidine-4-car boxylic acids, 1 in [3 + 2]-cycloaddition reactions via mesoionic oxaz olone (''munchnone'') intermediates. The chirality at C-4 of the start ing carboxylic acids 1 is eliminated in the products 3, and the chiral ity at C-3 (C-2 in the starting carboxylic acids 1) can thus be determ ined through chiroptical measurements. Several representatives of the ring system 3 have been characterised through H-1- and CD-spectra and the molecular structure of (3S)-3da has been determined by X-ray cryst allography.