Polypeptides. Part 17. Aminoxy-analogues of aspartame and gastrin C-terminal tetrapeptide amide

L- and D-2-Aminoxy-3-phenylpropionic acid have been prepared from D- and L-phenylalanine by a route which is generally applicable to other optically active amino-acids. Appropriate methodology enabled incorporation of the L-isomer in place of L-phenylalanine in Asp-Phe-OMe (to provide an aminoxy-analogue which was not sweet) and Trp-Met-Asp-Phe-NH2, (to provide an aminoxy-analogue which did not stimulate gastric acid secretion).