Conformational studies of antiradiation agents by NMR: cysteamine and its derivatives.

The conformations of cysteamine, thiazolidine, and thiazolidine-4-carboxylic acid were determined in aqueous solutions using NMR spectroscopy. At physiological pH, the population ratio of gauche- and trans-conformers was 3:1. The gauche-rotamer is probably responsible for the antiradiation activity and acts through metal chelation involving sulfur and nitrogen atoms. The puckering of the thiazolidine ring was calculated using NMR coupling constants. The observed results were compared with those obtained in the solid state using X-ray diffraction.