Biomolecules bearing the S- or SeAsMe2 function: amino acid and steroid derivatives

A series of molecules of the type GXAsMe2 have been synthesized in which X is S or Se and G is a moiety such as an amino acid, a di- or tripeptide, or a lipid. The compounds have been characterized by NMR, mass spectroscopy, and elemental analysis. Cysteine was found to react directly with dimethylarsinic acid to yield cystine and S-dimethylarsinocysteine (1). This reaction occurs also with other biomolecules containing thiol groups and raises serious questions concerning the use of cacodylate buffers in the study of enzyme kinetics and in sample preparation for electron microscopy. In the presence of dimethylchloroarsine and diethylamine, homocysteine thiolactone reacts to form both the dipeptide and the S-AsMe2 bond. Results of carcinostatic, bacteriostatic, and fungicidal testing of these compounds are reported. A hypothesis is advanced to explain the observed carcinostatic action of the dimethylarsino group.