2H-1,3-Oxazine-3(4H)-acetamide, N-[(1S,3S,4S)-4-[[2-(2,6-dimethylphenoxy)acetyl]amino]-3-hydroxy-5-phenyl-1-(phenylmethyl)pentyl]dihydro-.alpha.-(1-methylethyl)-2-oxo-, (alpha.3S)- AIDS-211891 AIDS211891