1.Towards the stereoselective synthesis of alpha-methylated (2S,3aS,7aS)-octahydroindole-2-carboxylic acid.
Sayago FJ1, Calaza MI, Jiménez AI, Cativiela C. Tetrahedron Asymmetry. 2008 Dec 12;19(24):2763-2766.
A high yielding and remarkably stereoselective alpha-methylation reaction of the (2S,3aS,7aS) stereoisomer of octahydroindole-2-carboxylic acid, (S,S,S)-Oic, suitably protected is described. The severe steric hindrance imposed by the fused cyclohexane ring, which prevents the application of Seebach's self-reproduction of chirality methodology, accounts for the formation of (S,S,S)-(alphaMe)Oic with high selectivity and retention of configuration.
2.A straightforward route to enantiopure alpha-substituted derivatives of (2S,3aS,7aS)-octahydroindole-2-carboxylic acid.
Sayago FJ1, Calaza MI, Jiménez AI, Cativiela C. Tetrahedron. 2009 Jul 1;65(27):5174-5180.
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.
