AIDS-005328 AIDS005328 Cyclohexanehexamide, .delta.-[(2-pyridinylcarbonyl)amino]-.gamma.-hydroxy-.alpha.-(1-methylethyl)-N-[2-methyl-1-[[(2-pyridinylmethyl)amino]carbonyl]butyl] U81749E analog psi-[CHOHCH2] cHexAla Val-Ile isostere