2,3a,11,13-Tetrakis(acetyloxy)-2,5,8,8-tetramethyl-12-methylene-4,9-dioxo-2,3,3a,4,5,8,9,10,11,12,13,13a-dodecahydro-1H-cyclopenta[a]cyclododecen-1-yl acetate AIDS-161439 AIDS161439 NSC691977