Infrared and Raman spectra (4000-100 cm-1) of solid samples of six different methyl substituted thiazolidine products of d-penicillamine and l-cysteine hydrochloride have been observed and assigned. Infrared spectra in D2O solutions have been obtained for comparison in order to study the amino-acid zwitterion equilibria. Proton and 13C nmr spectra for the compounds have also been measured.
