FORMAL SYNTHESIS OF HAPALINDOLE O AND SYNTHETIC EFFORTS TOWARDS HAPALINDOLE K AND AMBIGUINE A.

The formal synthesis of D,L-hapalindole O has been accomplished intercepting Natsume's total synthesis route. The intercepted substrate was synthesized in an overall 36% yield over ten-synthetic steps compared to Natsume's overall 1% yield over eighteen-synthetic steps. In addition, advanced substrates for the continuing progress towards hapalindole K and ambiguine A has been synthesized. All routes described herein employ a novel silyl ether-based strategy accessing the 6:5:6:6 ring system, that has previously been used in our laboratory to access the total synthesis of D,L-hapalindoles J and U.