S-Methyl-D-penicillamine

S-Methyl-D-penicillamine is a β-amino thiol derivative characterized by an S-methyl substitution on the thiol group of D-penicillamine, preserving the D-stereochemistry at the α-position. The molecule contains a primary amine, a methylated sulfhydryl group, and a three-carbon aliphatic chain. As a synthetic byproduct formed during penicillamine methylation processes, it exhibits distinct chromatographic properties due to steric hindrance from the methyl group. This compound functions as an HPLC reference standard for monitoring thiol methylation impurities in penicillamine drug substance analysis.