几种芳香型三环二萜化合物的半合成

Semi-synthesis of Some Aromatic Tricyclic Diterpenes

以(±)-13-甲氧基罗汉松烷-8,11,13-三烯(1)为起始原料,合成了5种三环二萜化合物2～6。化合物2的乙基由化合物1在-78℃及正丁基锂存在下,经溴乙烷乙基取代反应引入;在吡啶中用CrO3将化合物2氧化到得化合物3。在-78℃及正丁基锂存在下,化合物1用异丙基溴烷基化后,再经CrO3-HOAc溶液氧化得酮4;化合物4利用Jones试剂氧化得二酮5;化合物5在t-BuOK和t-BuOH中烯醇化为化合物6。化合物2～6均经1H NMR、13C NMR、IR、MS(EI)、HRMS、元素分析等表征所得数据与文献值相符。

Five tricyclic diterpenes（compounds 2, 3, 4, 5 and 6） were synthesized from （ ±）-13-methoxy- 8,11,13-podocarpatriene（ 1 ） via a simple approach, in which the ethyl group of compound 2 was introduced via alkyl substitution reaction when compound 1 was treated with n-BuLi and then reacted with ethyl bromide at - 78 ℃. The oxidation of compound 2 with CrO3 afforded compound 3 at - 78℃. Compound 1 was treated with n-BuLi, alkylated with i-propyl bromide and then oxidized by CrO3-HOAc to afford ketone 4. Diketone 5 was obtained by farther oxidation of ketone 4 using Jones reagent. Compound 6 was obtained by the enolization of compound 5 with the mixture of t-BuOK and t-BuOH. ^1H NMR, 13C NMR, IR, MS（EI）, HRMS and element analysis were used to confirm the structures of compounds 2 ~ 6, and the results are consistent with those in literature. In conclusion, the target compounds were successfully synthesized with the method in this paper.