5,6-Dimethyl-4-((5-methyl-1,1-dioxido-3-oxo-2-phenyl-1,2,6-thiadiazinan-4-yl)methyl)-2-phenyl-2H-1,2,6-thiadiazin-3(6H)-one 1,1-dioxide AIDS-137755 AIDS137755 NSC642971