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-octenoic acid and (2S,4R)-2-amino-4-methyl-hexanoic acid have been prepared using the acetonide of D-Serine aldehyde 1 as a formyl glycine equivalent. 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