EFFICIENT SYNTHESES OF YUEHCHUKENE AND BETA-(DEHYDROPRENYL)INDOLE

Yuehchukene (1) has been synthesized by one-step transformations of both alcohols (E)-beta-(3-hydroxy-3-methylbutenyl)indole (3) and beta-(1-hydroxy-3-methylbut-3-enyl)indole (4) under various reaction conditions. Alcohol 3 can be prepared efficiently from indole-3-carboxaldehyde (8) via a two-step reaction sequence. Alcohol 4, an isomer of 3, can be obtained from the same starting materials 8 in only one step. Alcohol 4 can be converted directly into beta-(dehydroprenyl)indole (2) in high yield under mild conditions via a base-induced dehydration. However, alcohol 3 does not give diene 2 under the same reaction conditions. Since diene 2 has been used as the key intermediate for the syntheses of yuehchukene (1), analogues of 1, and a cytotoxic compound, murrapanine (7), our present work also completes formal total syntheses of these bioactive compounds.