Nickel and Palladium Catalysis in the Stereoselective Synthesis of Functionalized Pyrrolidines: Enantioselective Formal Synthesis of (+)-α-Allokainic Acid.

Neuroexcitatory natural products are accessible from 1 via the intermediate 2, which is obtained by Ni-catalyzed cyclization, transposition of the protecting group, and Pd-catalyzed reduction with allylic transposition. This stepwise formation of stereocenters allows a highly direct and stereoselective synthesis of the excitatory amino acid (+)-α-allokainic acid, which displays an all-trans arrangement of the substituents about the pyrrolidine ring. TBS=tert-butyldimethylsilyl.