EFFICIENT SYNTHESES OF THE MARINE ALKALOIDS MAKALUVAMINE-D AND DISCORHABDIN-C - THE 4,6,7-TRIMETHOXYINDOLE APPROACH

A new and efficient synthesis of the tricyclic quinonimine 20 as its t rifluoroacetate 23 has been developed starting from the commercially a vailable 2,4,5-trimethoxybenzaldehyde and proceeding via the hitherto unknown 4,6,7-trimethoxyindole (7). Quinonimine 23 is the late stage k ey intermediate in several previously reported syntheses of the biolog ically active pyrrolo[4,3,2-de]-quinoline marine alkaloids discorhabdi n C (1) and makaluvamine D (3).