Novel furanoid alpha-substitued alpha-amino acid as a potent turn mimic in peptide synthesis

A stereoselective approach has been developed to the new sugar amino acid and potential potent turn mimic 5-O-(tert-butyldimethylsilyl)-3-deoxy-1,2-O-isopropylidene-3-methoxycarbonylamino-alpha-D-xylofuranose 3-C-carboxylic acid (12), via the [3,3]-sigmatropic rearrangement of allylic thiocyanates (Z)-6 and (E)-7, prepared from D-xylose. The synthesis of a new dipeptide 13 is also described.