52 フムレンのコンホメーションと反応

概要

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Molecular mechanics calculation was performed on four stable conformations of humulene (CT, CC, TT, TC). Their heats of formation and atomic coordinates were obtained and the former two (CT, CC) were found to be equally more stable than others. These findings suggest that biosynthetically hirsutene is directly derived from the CC form of humulene rather than from the CT form through protoilludene. A process in which the three double bond planes rotate successively by 180°was proposed as the mechanism for interconversion of D- and L- forms of humulene. The energy barrier to the interconversion was estimated by the molecular mechanics calculations and shown to be 18.64kcal/mol. Humulen-9,10-epoxide was found to be converted to 6-acetoxyhumulen-7-ol on treatment with BF_3-AcOH. A possible reaction route was presented and was supported by isolation of the assumed intermediate 5. The steric courses of this and other transannular cyclization reactions of humulene were examined. In most of these reactions the stable conformation of reactant is conserved throughout the reactions.
天然有機化合物討論会の論文
1978-08-22