Sulfinimine-mediated asymmetric synthesis of (R)-(4-methoxy-3,5-dihydroxyphenyl)glycine: The central amino acid of vancomycin and related agents

The sulfinimine asymmetric Strecker synthesis, the addition of ethyl aluminum cyano alkoxide, "EtAl(OR)CN", to sulfinimine 10, has been applied to a concise highly efficient four-step enantioselective synthesis of (R)-(4-methoxy-3,5-dihydroxyphenyl)glycine (3) and its derivatives in >97% ee. These epimerization-sensitive arylglycines are precursors of the key central amino acid of vancomycin and related glycopeptide antibiotics.