Thiazolidine-4(R)-carboxylic acids derived from sugars: Part I, C2-epimerisation in aqueous solutions.

Article abstract of DOI:10.1016/0008-6215(89)80005-9

Reactions of L-cysteine (1) with L-xylose, D-ribose, D-lyxose, D-arabnose, D-glucose, L-rhamnose, and-fucose in aqueoes ethanol yielded crystalline 2(S)-(polihydroxyalkyl)thiazolidine-4(R)-carboxylic acids.Likewise, glycolaldehyde and L-glyceraldehyde, D-xylose, L-arabinose, D-mannose, D-galactose, and D-fucose gave crystalline 2(R),4(R) epimers.The reaction of 1 and D-glycerinaldehyde gave a syrup mixture of 2(S),4(R) and 2(R),4(R) compounds.The same substrates, but with no ethanol present, gave the 2(S),4(R) epimers for glycolaldehyde, L-xylose, L-fucose, and L-arabinose, and the 2(R),4(R) epimers for D-lyxose, L-rhamnose, D-mannose, Dgalactose, and D-fucose.The reactions of D-ribose, D-arabinose, D-xylose, and D-glucose gave sirupy mixtures of epimers.The crystalline reaction products, when dissolved in water, undergo rapid epimerisation as reflected by mutarotation and changes in the 1H- and 13C-n.m.r. spectra.