The title compound was synthesized by the diastereoselective addition of the lithium or sodium anion of dimethyl methylphosphonate to fi-trityl-L-phenylalaninal. Inhibition of renin, an aspartic proteinase, is a current area of intense research. 1 Incorporation of statine (1) (R = L -pr), and derivatives thereof, into an appropriate peptide sequence has led to the discovery of very potent renin inhibitors. * We wished to investigate the effect of replacing the CI-carboxyl of statine with a phosphonyl group. In considering I 3 2 synthetic approaches to these derivatives one would ideally wish to control both the relative and absolute sense of asymmetry at the C2-hydroxy and C3-amino centers. In this letter we wish to report the first diastereo-and enantioselective preparation of a phospho-statine derivative. It was hoped that 2 could be prepared by analogy to the literature syntheses of statine.3a Preliminary investigations were begun with BOC-L-phenylalininol (3) to take advantage of the UV tag during isolation of the products. Swern oxidation4 of 3 (reaction was run and quenched at -60ยฐC) provided BOC-L-phenylalininal (4) which was immediately added in dry tetrahydrofuran (THF) to a -78ยฐC solution of the lithium or sodium anion of dimethyl methyl phosphonate (5) (1.1 eq. n-BuLi or NaHMDS, 1.2 eq. CH3PO(OCH3)2, THF, -78"C, 0.5 h) (eqn. l).3b After 0.25 h at -78ยฐC the reaction was quenched (excess satd. aq. NH4Cl) and the products isolated by a typical extractive process to provide consistently modest yields (15-30%)5 of the desired phospho-