New fast and practical method for the enantioselective synthesis of alpha-vinyl, alpha-alkyl quaternary alpha-amino acids

摘要

We describe a fast and practical enantioselective synthesis of (S)-N-Cbz-alpha-vinyl, phenylalanine, suitable for the preparation of different N-Cbz-alpha-vinyl aminoacids of both configurations. The new protocol exploits a Wittig reaction on highly enantiomeric enriched N-Cbz-alpha-formyl-alpha-alkyl amino esters, readily accessible from (L)-serine through a stereoselective alkylation of Seebach's oxazolidine, carried out with a significant improvement of the previously reported method. The synthetic scheme is suitable for gram scale preparation of the desired product with a 94% ee. (C) 2008 Elsevier Ltd. All rights reserved.