Some reactions of N-Ethylmaleimide

The reactions of N-ethylmaleimide (NEM) with the amino group of peptides, with imidazole and with cysteine have been investigated. With the first two classes of compound, an IN-acylation reaction appears to occur, followed in the case of imidazole by a catalytic polymerization of NEM. With cysteine, reaction proceeds through addition of the thiol to the olefinic bond of NEM; in alkaline solution, the cysteine adduct undergoes all intramolecular transamidation reaction to form a thiazane derivative.