(S)-2-{3-[(2R,3R)-3-((S)-1-Benzyloxycarbonylamino-2-phenyl-ethyl)-oxiranyl]-2-oxo-propanoylamino}-3-methyl-butyric acid AIDS-070509 AIDS070509 Cbz-Phe- .psi.[(R,R)-cis-epoxide-C(=O)]-Val