AIDS-142973 AIDS142973 Ethyl 9,10-dimethoxy-1-(2-methoxyvinyl)-3,4-dioxo-1-((trimethylsilyl)oxy)-1,2,3,4,6,7-hexahydro-2aH-cyclobuta[2,3]pyrrolo[2,1-a]isoquinoline-2a-carboxylate NSC661966