Enantiomeric enrichment of α-amino acid derivatives: recrystallization of N-Fmoc α-amino acid tert-butyl esters

The optical purity of products derived from enantioselective reactions of the benzophenone imine of glycine tert-butyl esters can often be improved by conversion to the N-Fmoc α-amino acid tert-butyl esters followed by simple recrystallization.