A straightforward route to enantiopure alpha-substituted derivatives of (2S,3aS,7aS)-octahydroindole-2-carboxylic acid

High yielding and remarkably selective alkylations of a suitably protected derivative of (2S,3aS,7aS)-octahydroindole-2-carboxylic acid are described. The fused bicyclic structure of this proline analogue greatly influences the stereochemical outcome of direct alkylation reactions taking place at the alpha-carbon and provides access to alpha-substituted analogues with retention of the configuration. The overall procedure allows the preparation of enantiopure alpha-substituted derivatives of this Oic isomer, suitably protected for their incorporation into Peptides, in a straightforward manner.