Beyeranes, Kauranes, Atisanes, and Trachylobanes

The reaction of trachylobane (273) with protic acids gives rise to products of both the atiserene and kaurene types, the former usually being favored to a substantial extent 329, 330). Thus, cleavage of the two more highly substituted cyclopropane bonds occurs with protonation at the respective less high substituted positions (C12 and Cie) so as to generate tertiary cations. The apparent preference for C16 protonation 

Under the kinetically controlled conditions of the solvolysis reactions and amine deamination, there is no evidence for either 1,3-hydrogen elimination to trachylobane or 1,3-hydrogen shift. Trachylobane formation (12%) has, however, been observed in the decomposition of the tosyl-hydrazone (279) under high temperature, protic conditions 346). Since aprotic decomposition (presumably via carbene), produces only olefinic products, it would appear that the cyclopropane ring is formed through a cationic pathway. 

Conversion of kaurene and beyerene to the atiserenes has been observed after prolonged exposure of the diterpene hydrocarbons to hydrogen chloride in chloroform (6-14% after 4-21 days at 25% 330). Similarly prolonged solvolysis (25°, 20 hr.) of the beyerane tosylate 275-OTs (with C4-CO2CH3) 346) or kaurene 331) in buffered trifluoroacetic acid, a medium of relatively low nucleophilicity, affords (after saponification) 

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