10-Hydroxy-1-[2-(1-methylethyl)-4-thiazolyl]-5-(1-methylethyl)-3,6-dioxo-8,11-bis(phenylmethyl)-2,4,7,12-tetraazatridecan-13-oic acid, 3-pyridinyl ester A-83962 AIDS-028481 AIDS028481 Ritonavir deriv.