4-(2-Acetylamino-4-tert-butoxycarbonyl-butyrylamino)-4-(1-{1-[5-(1-allylaminooxalyl-butylcarbamoyl)-1-ethoxycarbonylmethyl-2-oxo-imidazolidine-4-carbonyl]-2-methyl-propylcarbamoyl}-2-methyl-propylcarbamoyl)-butyric acid, tert-butyl ester AIDS-222889 AIDS222889