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.