Isopropenyl chlorocarbonate (IPCC)1 in amino acid and peptide chemistry: Esterification of N-protected amino acids; Application to the synthesis of the depsipeptide valinomycin
Esterification of N-protected α-amino acids was achieved via isopropenyl chlorocarbonate (IPCC) activation. In situ alcoholysis of the unstable mixed anhydride intermediate was catalyzed by 4-(dimethylamino)pyridine (DMAP). Competing isopropenyl ester formation was negligible when using methylene chloride as the solvent. A variety of esters from primary and secondary alcohols were obtained with good