Abstract
Application of diphenyl phosphorazidate (DPPA) to the synthesis of peptides revealed that the DPPA method is quite general because it can be applied to the formation of peptides containing various functional groups. No difficulties were encountered when the side chains of serine, threonine, valine, glutamine, asparagine, methionine, histidine, tryptophan, and pyroglutamic acid were present in the carboxyl component. Arginine and cysteine showed no trouble when their side chain functions were protected with the nitro and benzyl groups, respectively. Serine, tyrosine, and histidine could be used as the amino component without any protection of the side chains. Fragment coupling of N-benzyloxycarbonylleucylleucine with valylphenylalanine methyl ester hydrochloride by DPPA showed that no racemization occurred.
