Chemical Transformation of Terpenoids. II. Acid Treatment of (3S)-1-Vinyl-, (3S)-1-Hydroxypropenyl-, and (3S)-1-Epoxyethyl-1,2,2-trimethylcyclopentane Derivatives : Ring Enlargement Reactions and Successive Migrations of Methyl Residues

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Four 1,2,2-trimethylcyclopentane derivatives, (+)-(1S, 3S)-3-acetoxymethyl-1,2,2-trimethyl-1-vinylcyclopentane (3), (+)-(1S, 3S)-3-acetoxymethyl-1-(3'-hydroxypropenyl)-1,2,2-trimethylcyclopentane (4), (+)-(1R, 3S, 1'S)-3-acetoxymethyl-1-(1', 2'-epoxyethyl)-1,2,2-trimethylcyclopentane (5), and (+)-(1R, 3S, 1'R)-3-acetoxymethyl-1-(1', 2'-epoxyethyl)-1,2,2-trimethylcyclopentane (6), which were synthesized from d-camphor (1), were subjected to acid treatment. It was found that i) treatment of 3 with 2,4,4,6-tetrabromocyclohexa-2,5-dienone yielded a cyclohexane derivative (7) which was formed via a ringenlargement reaction sequence, ii) BF_3-etherate treatment of 5 furnished three cyclopentane derivatives (14,15,16), among which 14 and 15 possess a 2-oxa-bicyclo [3.3.0]-octane skeleton produced through successive migrations of methyl groups, and iii) BF_3-etherate or titanium tetrachloride treatment of 6 resulted in a ring-enlargement reaction giving 19 and 20,or 21.
社団法人日本薬学会の論文
1981-09-25