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 Lamino 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.