4,10-Etheno-6H-thieno[2,3-d][1,2,4]triazolo[1,2-a]pyridazine-3a(4H)-carboxylic acid, 10,11-dicyano-2,3,7,8,10,10a-hexahydro-6,8-dioxo-7-phenyl-4-[(triphenylphosphoranylidene)amino]-, ethyl ester AIDS-134609 AIDS134609 NSC633120