Novel Rearrangements of Sesquiterpenoid Panasinsane Derivatives under Acidic Conditions

The sesquiterpenoid panasinsane derivatives 11 and 14−16 have been prepared from caryophyllene oxide (7). The novel rearrangement reactions of compounds 11 and 14 under TCNE-catalyzed solvolysis conditions and the reactions of compounds 15 and 16 under superacid conditions (HSO3F/Et2O, −63 °C) have been investigated. The ginsenol derivative 17 is obtained from compounds 11 and 14 under TCNE-catalyzed conditions. The rearrangement of compounds 15 and 16 under superacid conditions leads to the novel sesquiterpene derivatives (1S,4S,7S,10S,11S)-3,3,10,11-tetramethyltricyclo[5.3.1.04,10]undecan-1,11-yl sulfate (19) and (1S,4S,5S,8S)-2,2,4,8-tetramethyl tricyclo[3.3.2.14,8]undecan-11-one (20). The influence of the secondary hydroxyl group at C-5 of the panasinsane derivatives on the course of these rearrangements is discussed.