33 The Photosensitized Oxygenation of Sesquiterpenes with α-Vinylcyclopropane Ring : Biogenetic Type Oxygenation to Terpenoids
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Photo-sensitized oxidation of thujopsene (I), thujopsenol (III) and gurjunene (VI) were carried out in order to examine the effect of difference in the molecular geometry and other stereochemical features upon the reaction with singlet oxygen. The result also revealed the following points: i) The preferred conformation of I and all the derivatives is I_A except C_2. ii) Dioxetane or its equivalents is responsible for the cleavage of C=C bond. iii) The cleavages of cyclopropane ring were observed in the reaction of VI. iv) Thujopsadiene (II) and mayurone (IV) were prepared in a single step which may have biogenetic significance. v) VI was converted to zierane skeleton.
