Synthesis of 15N-labelled chiral Boc-amino acids from triflates: enantiomers of leucine and phenylalanine

Abstract

An efficient synthesis of ¹⁵N-labelled chiral Boc-amino acids by triflate alkylation of di-tert-butyl [¹⁵N]imidodicarbonate is reported. Both enantiomers of Boc-leucine and -phenylalanine were synthesized from commercial α-amino acids of opposite configuration viaα-hydroxy carboxylic acids provided by diazotization, thus extending the scope of an earlier exploratory study. The high chiral purity of the final products was confirmed by HPLC. These labelled amino acid derivatives are suitable for direct application to the synthesis of labelled peptides.