A new two-step synthesis of Fmoc-protected N-alkyl amino acids has been developed. The first step involves acid-catalyzed condensation of an Fmoc-protected amino acid with an aldehyde to form an oxazolidinone. This intermediate is then reduced with triethylsilane and trifluoroacetic acid to the N-alkylated derivative. The procedure is applicable to a variety of amino acids and aldehydes and results in less than 0.1% racemization as measured by a ...