天然有機化合物討論会講演要旨集
Online ISSN : 2433-1856
セッションID: 29
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29 分子内デッツ反応を用いたケンドマイシンの全合成(口頭発表の部)
田中 教介渡辺 将仁藤森 友紀子石橋 広大小澤 友宏松山 拓史犀川 陽子中田 雅也
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会議録・要旨集 フリー

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Kendomycin (1), an ansa-type compoung having a unique quinone methide portion connected to a highly-substituted tetrahydropyran, was isolated from Streptomyces species. 1 possesses a potent activities as an endothelin receptor antagonist and an antiosteoporotic compoung as well as antibacterial and cytotoxic activities. Herein, we report the total synthesis of kendomycin (1) featuring the intramolecular Dotz(Doetz) reaction. We anticipated that the intramolecular Dotz reaction of Fischer chromium carbene complex 2 would afford oxametacyclophane 3 (Scheme 1). Actually, the intramolecular Dotz reaction using the simple substrate 6 produced the desired oxametzcyclophane 7 with exclusive regioselectivity (Scheme 2). Further, more complicated substrates 19 and 22 were applied to the reaction as model studies of kendomycin (1) synthesis. The intramolecular Dotz reaction of 19, containing all substituents in the tetrahydropyran portion, proceeded with high regioselectivity to give the oxametacyclophane 20 (Scheme 3). Subsequent cyclization of the product was diastereoselectively performed, affording 21. Also in the case of 22 having the foothold for the construction of the p-quinone methide portion, the intramolecular Dotz reaction proceedee with high regioselectivity to give the oxzmetacyclophane 23 (Scheme 4). The p-quinone 27 was synthesized from 23 in seven steps containing IBX oxidation of phenol. Ring closure and tautomerization was easily performed by applying 27 on the silica gel TLC to give the p-quinone methide 28. Based on the above results, we challenged the total synthesis of kendomycin (1)(Scheme 5-8). The Suzuki coupling of the left half segment 36, synthesized from 29, and the right half segment 40, derived from the ent-29, gave 41 in excellent yield. Diastereoselective tetrahydropyran-ring formation and the protecting group manipulation of 41 afforded the precursor of the chromium carbene complex. The resulting 48 was converted to the carbene complex 49 and it was subjected to the intramolecular Dotz reaction to give the desired oxametacyclophane 50 in good yield. After oxdative cleavage of terminal olefin followed by the Claisen rearrangement, the resulting 52 was oxidized with IBX and applied on silica gel, giving p-quinone methide 54. After deprotection of TBS group as the last step, we accomplished the total synthesis of kendomycin (1).

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