A stereochemical study of optically active thiazolidines

We report a stereochemical study of a series of free N-H and N-methylated 1 ,3-thiazolidines heating H or CH, at C-(2). These compounds were readily pr epared from ephedrine and pseudoephedrines. The stereochemistry of the comp ounds under study was deduced using H-1 and C-13 NMR spectroscopy. Two isom ers were found for compounds having a methyl group at C-(2) (i.e. C-(2)HCH3 ): interconversion of these isomers, presumably via a non-cyclic zwitterion ic intermediate, was observed. (C) 2001 Elsevier Science Ltd. All rights re served.