A synthesis of the pyrrolidine alkaloid (-)-ruspolinone (1) from (2S)-proline in 7 steps and 26% overall yield is presented which assigns the (2S) configuration to (-)-(1). The compound obtained by this route has [alpha]D-29.73-degrees compared to a value of zero for the material isolated from the plant suggesting racemisation had occurred during isolation.
intramolecular aza-Michael addition with enone carbamates catalyzed by chiral Brønsted acids was developed. A domino cross metathesis/aza-Michael addition for the preparation of 2-substituted pyrrolidines or benzopyrrolidines was also explored. The reactions described here provide an efficient asymmetric protocol for enantio-enriched heterocycles, especially 2-substituted pyrrolidines.