40 THE AROMATISATION REACTION OF Δ^<7,9(11)> TRITERPENOIDS
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In order to correlate fernane and arborane groups of triterpenoids, the 'anthrasteroid'-type rearrangement of bauera-7, 9(11)-dienyl acetate (3b) was reexamined and the product was proved not to be (4) but to be expressed by (5). The same hydrocarbon (5) was also obtained from the dienol (3c) and from the methyl ether (3d). The structure (5) was confirmed by the derivation of (3c) to a fivemembered ketone (10) through the triene (7), which formed (5) by the acid-treatment. The same aromatisation reaction was applied for 7, 9(11)-dienes (11-14) of tirucallane, lanostane, fernane, and arborane series and the same type of hydrocarbons (15-18) were obtained in good yields. The configuration of the isopropyl group in (5, 15-18) was examined by the ORD curves. An aromatisation reaction of a novel type of (3b), bauerene (6a), arundoin (1), and cylindrin (2) by dibromodimethylhydantoin-γ-collidine was examined and the formation of styrene type compounds (24-27) was suggested.
