AIDS-005326 AIDS005326 Cyclohexanehexamide, .delta.-[(1-oxohexanylamino)-.gamma.-hydroxy-.alpha.-(1-methylethyl)-N-[2-methyl-1-[[(2-pyridinylmethyl)amino]carbonyl]butyl] U81749E analog psi-[CHOHCH2] cHexAla Val-Ile isostere