Synthesis of C-glycosyl amino acids:: scope and limitations of the tandem Tebbe/Claisen approach

Amino acids may be used as coupling partners for esterification with 3-hydroxy galycals as substrates for the tandem Tebbe/Claisen approach to the synthesis of C-glycosyl amino acids. Whilst esters of substituted at-amino acids do not successfully undergo Tebbe, or other, methylenation, esters of beta- or gamma-amino acids are methylenated to yield vinyl ethers. which then undergo smooth thermal rearrangement to yield beta-C-glycoside products. tert-Butyl esters are found to be unreactive to the Tebbe reagent, and as such tert-butyl protection may be used for other carboxylic acids. (C) 2004 Elsevier Ltd. All rights reserved.