Enantioselective Addition of Ketene Silyl Acetals to Nitrones Catalyzed by Chiral Titanium Complexes. Synthesis of Optically Active <i>β</i>-Amino Acids
A chiral titanium complex, Ti(O-i-Pr)(4)/BINOL/tert-butylcatechol, catalyzesenantioselective addition reaction of ketene silyl acetals to nitrones to give optically active beta-amino acid derivatives which are biologically active compounds and useful synthetic intermediates of natural products and pharmaceuticals such as beta-lactam antibiotics. The combined process of catalytic oxidation of secondary