(2R,5R)-4,5-Diacetyloxy-6-(acetyloxymethyl)-2-(2-methyl-1,3-dioxoindolo[2,3-a]3-pyrrolino[3,4-c]carbazol-9-yl)perhydro-2H-pyran-3-yl acetate AIDS-058758 AIDS058758 Rebeccamycin analog