Synthetic Anthracyclines: Regiospecific Total Synthesis of a D-Ring Indole Analogue of Daunomycin.

The 4-methoxy-5-methylpyrano[3, 4, -b]indole-1, 3(4H, 5H)-dione (9), prepared from methyl 3-methoxycarbonyl-1-methylindol-2-yl acetate (6), underwent a strong base-induced cycloaddition reaction with 2-chloro-6, 6-ehylenedioxy-5, 6, 7, 8-tetrahydro-1, 4-naphtoquinone (11) to give the tetrahydronaphtho[2, 3-b]carbazole-7, 12-dione (10), regioselectively. The cycloadduct (10) was successfully converted to a D-ring indole analogue of daunomycin (1a).