Practical synthesis of novel phosphonopeptides containing Aib(P)

Practical and convenient method for the synthesis of novel phosphonopeptides 8a-h and 10a-f incorporating the quaternary α-aminophosphonate 6 is reported. The target compounds were prepared in moderate to good yield based on the preparation of the quaternary α-aminophosphonate 6 followed by the formation of the α-bromoamide 7 and subsequent nucleophilic substitution reaction with several amines or by peptide bond formation with several amino acids and with the quaternary α-aminophosphonate 6, using isobutyl chloroformate as activating agent under racemization-free condition.