The total synthesis of D,L-hapalindoles J and U has been accomplished. Hapalindole J was prepared in 11% overall yield over 11 synthetic steps and hapalindole U was prepared in 25% overall yield over 13 synthetic steps from commercially available materials. The route employs a novel silyl ether-based strategy for accessing the 6:5:6:6 ring system of the hapafindoles rapidly and in good yields.
A total, synthesis of marine indole alkaloids (±) -hapalindoles H (1) and U (2) was achieved from the previously described compound 7 by way of 13, 21, and 26 for U (2), and 33 and 32 for H (1).