Dysobinin

Anthothecol (94) and hirtin (95) have been interrelated via the trione (96). Dysobinin (97) is a new tetranortriterpenoid from Dysoxylum binectariferum7 An intermediate in a projected limonoid synthesis has been shown to have structure (98) by X-ray analysis. ... 

These considerations show that the structure assigned to dysobinin 181) is incorrect. Dysobinin was considered to be 6p-acetoxyazadirone (4). However, the methyl group farthest downfield resonates at 5 1.3, while use of model compounds 152) shows that an axial acetoxy group at C-6 should produce a downfield shift of the C-10 methyl group to approximately 5 1.5. The 6a-configuration is predicted to lead to the observed shift 64). The structure of 6p-acetoxyobacunol (5) 201), although unusual, appears to be correct as the methyl shifts recorded agree with those calculated. 

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