Cleavage of dehydroalanine-containing peptides with mercuric acetate

The dehydroalanine containing peptides glycyldehydroalanine and t-butyloxy-carbonyl-L-alanyldehydroalanyl-beta-methyl-D, L-aspartic acid methyl ester were synthesized, respectively, from chloroacetamide and pyruvate and from t-butyloxycarbonyl-L-alanyl-S-methyl-L-cysteinyl-beta-methyl-D, L-aspartic acid methyl ester. They were reacted with mercuric acetate in water, 50% methanol and dimethylformamide at 25 degrees and at 80 degrees for various time periods. Reaction proceeded to yield an amino acid amide from the N-terminal side of the unsaturated residue and pyruvate from the C-terminal side. Yields of amino acid amides were 76% for the dipeptide and 40% for the tripeptide. The applicability of the neutral reaction conditions employed to the cleavage of glycoproteins containing both O- and N-glycosidically-linked carbohydrate chains following beta-elimination of the serine and threonine linked oligosaccharides is pointed out.