Peptide synthesis using carbamoylmethyl esters as acyl donors mediated by Bacillus amyloliquefaciens protease.

Bacillus amyloliquefaciens protease-catalyzed peptide bond formation was investigated using the carbamoylmethyl (Cam) ester as the acyl donor. A series of N-protected L-amino acid Cam esters were coupled with an L-amino acid amide in acetonitrile in good to excellent yields. The superiority of the Cam ester for segment condensations was demonstrated in several 2+1 couplings. Furthermore, the couplings of racemic amino acid Cam esters as carboxyl components afforded the L-L-peptides in a highly diastereoselective manner.