AIDS-137255 AIDS137255 NSC641108 Phosphinous acid, diphenyl-, 5,11,17,23-tetrakis(1,1-dimethylethyl)pentacyclo[19.3.1.1~3,7~.19,13.1~15,19~]octacosa-1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23-dodecaene-25,26,27,28-tetrayl ester