A Facile and General Entry to C-Glycosyl (R)- and (S)-(beta)-Amino Acid Pairs from Glycosyl Cyanides through Enamino Ester Intermediates

Four O-perbenzylated glycosyl cyanides ((alpha)- and (beta)-d-mannopyranosyl, (alpha)-d-galactopyranosyl, and (alpha)-d-arabinofuranosyl) were converted by treatment with BrCH2CO2Et/Zn in THF at reflux (Blaise-Kishi reaction) into the corresponding C-glycosyl (beta)-en­amino esters which in turn were reduced by NaBH(OAc)3 to give four pairs of C-glycosyl (R)- and (S)-(beta)-amino esters.