Asymmetric Synthesis of Quaternary (E)-Vinylglycines

Significance

Chiral quaternary (E)-vinylglycines can be prepared in two steps from simple aldehydes. The method offers an alternative to those of Seebach and co-workers (Helv. Chim. Acta 1987, 70, 237-261) or Berkowitz and co-workers (J. Org. Chem. 2000, 65, 2907-2918). The dienolate of 2 alkylates the electrophile R² regioselectively at the α-position, and yields the olefin in the trans geometry only.