The proline-catalyzed asymmetric Amination of branched aldehydes

An efficient access to configurationally stable alpha,alpha-disubstituted alpha-amino aldehydes, oxazolidinones, and alpha-amino acids has been presented. Starting from simple and easily available racemic aldehydes, the alpha-aminated products were obtained using azodicarboxylates as the nitrogen source in up to 86% ee and moderate to excellent yield. These products could further be converted both into the corresponding alpha-amino alcohols and, depending on the residue of the azodicarboxylates and the reaction conditions, into the oxazolidinones. On the other hand, oxidation towards the carboxylic acid and cleavage of the hydrazide bond under mild conditions revealed the free alpha-alkylated phenylglycine derivative. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).