STEREOCONTROLLED SYNTHESIS OF GAMMA-BRANCHED AMINO-ACIDS - TICL4 MEDIATED ADDITION OF (E)-CROTYLSILANE TO N,O-PROTECTED SERINE ALDEHYDE

The N-Boc derivatives of 2S,3S,4R,6E)-2-amino-3-hydroxy-4-methyl-6-oct enoic acid and (2S,4R)-2-amino-4-methyl-hexanoic acid have been prepar ed using the acetonide of D-Serine aldehyde 1 as a formyl glycine equi valent. The stereochemistry of the y-branch was introduced by reaction of (E)-crotyltrimethylsilane with 1 in the presence of TiCl4 followed by elaboration of the terminal double bond and further transformation of the Serine hydroxymethyl group into a carboxylic acid. Copyright ( C) 1996 Elsevier Science Ltd