Diastereoselectively switchable enantioselective trapping of carbamate ammonium ylides with imines.

The diastereoselectively switchable enantioselective trapping of protic carbamate ammonium ylides with imines is reported. The intriguing Rh(2)(OAc)(4) and chiral Brønsted acid cocatalyzed three-component Mannich-type reaction of a diazo compound, a carbamate, and an imine provides rapid and efficient access to both syn- and anti-α-substituted α,ß-diamino acid derivatives with a high level control of chemo-, diastereo-, and enantioselectivity.