Abstract A sulfonamide-based protecting group (PG),(9H-fluoren-9-yl) methanesulfonyl (Fms), which can be used in a similar way to the well-established Fmoc PG, was 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 ...
