developed. The advantages of this new PG were demonstrated in the successful formation of a phosphonamide between an N-Fms-protected α-phosphonoalanine monoester and secondary alkylamines, including (R)-2-phenylethylamine, (S)-phenylalanine tert-butyl ester (H-Phe-OtBu), H-Pro-Gly-OtBu, and H-Phe-Phe-OtBu, without formation of oxazaphospholine, which is a serious problem associated with the Fmoc PG