Synthesis of chiral N-trifluoroacetyl-methionine derivatives and applying them as acyl donors for Friedel-Crafts acylation

A chiral N-protected alpha-amino acid N-hydroxysuccinimide ester (OSu) is a common useful reagent for peptide bond formation. Recently, N-trifluoroacetyl (TFA) alpha-amino acid OSu esters have been reported as acyl donors for Frieldel-Crafts reactions to synthesize chiral alpha-amino phenyl ketones retaining the configurations of the starting alpha-amino acids. There are few reports for chiral TFA protected methionine, which has methylthioethyl structure in the side-chain of the alpha-amino acid. The detailed synthesis of chiral TFA-Met-OSu and its application as an acyl donor for Friedel-Crafts acylation is reported.