Marine Sesquiterpene Quinones and Hydroquinones: Acid-Catalyzed Rearrangements and Stereochemical Investigations

Abstract

Acid treatment of both ilimaquinone (3) and 5-epi-ilimaquinone (9) yielded the same rearrangement products, (7) and (8), thus defining a common absolute stereochemistry. Likewise, acid- catalysed rearrangement of avarol (10) and arenarol (11) yielded the common product aureol (13), allowing the absolute stereochemistry of arenarol (11) and its related quinone arenarone (12) to be assigned. This latter acid- catalysed rearrangement also yielded an unexpected electrophilic aromatic cyclization product (15), the dimethyl ether (17) of which could be obtained in quantitative yield from acid treatment of avarol dimethyl ether (16).