We report here a convenient and simple solid-phase synthesis of
N-nosyl-
N-methyl-
-amino acids and
N-Fmoc-
N-methyl-
-amino acids, important building blocks for the synthesis of conformationally restrictedand protease-resistant natural peptides and peptide analogues. The methodology involves the use of2-chlorotrityl chloride resin to temporarily protect the carboxylic group of
-amino acids and ofdiazomethane as the reagent to methylate the sulfonamidic function. The approach developed is particularlyefficient also with
-amino acids bearing appropriately protected functionalized side chains.