113(P50) 8および9員環ブロモエーテル系天然物の合成研究(ポスター発表の部)

概要

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As part of our studies on the total synthesis of laurallene (1) and obtusenyne (3), we describe here the stereoselective synthesis of 9-membered cyclic bromo and hydroxy ethers starting from the related dienol ethers through oxidative acetalization, followed by reduction, as well as our attempts to apply the method to an 8-membered ring system. Treatment of dienolethers 15 and 23 with NBS or mCPBA in methanol easily produced the respective bromoacetals 16 and 24 or hydroxyacetals 17 and 25. Reduction of 9-membered acetals 16 and 18 with triethylsilane and tin(IV) chloride to give stereoselectively r-2, c-9-diethyl-t-3-substituted-Δ^5-oxonenes 19 and 21, respectively, while the treatment of 8-membered acetals 24 and 25 gave only acyclic ethers. When dimethyldioxirane was used as another oxidant, 15 was cleanly converted to 28, which was fairy stable under neutral conditions. After solvent exchange, reduction of 28 with DIBAH produced r-2, t-9-diethyl-t-3-hydroxy-Δ^5-oxonene (29). The novel stereospecific transformation of r-2, c-9-diethyl-t-3-hydroxy-Δ^5-oxonene (21) to trans-2-(1-bromopropyl)-Δ^4-oxocene (34) is also described.
天然有機化合物討論会の論文
1996-09-02