Department of Chemistry, University of California , Berkeley, California 94720, United States.
Org Lett. 2017 Sep 1;19(17):4632-4635. doi: 10.1021/acs.orglett.7b02260. Epub 2017 Aug 18.
A synthetic strategy to access the fused 6-7-6 tricyclic core of hetisine-type C-diterpenoid alkaloids is reported. This strategy employs a Diels-Alder cycloaddition to assemble a fused bicyclic anhydride intermediate, which is elaborated to a vinyl lactone-acetal bearing an aromatic ring in five steps. Aromatic iodination is followed by magnesium-halogen exchange with a trialkyl magnesiate species, which undergoes intramolecular cyclization. Subsequent oxidation provides the desired 6-7-6 tricyclic diketoaldehyde, with carbonyl groups at all three positions for eventual C-N bond formation and subsequent elaboration.
本文报道了一种构建 hetisine 型 C-二萜生物碱稠合 6-7-6 三环核心骨架的合成策略。该策略采用 Diels-Alder 环加成反应构建一个稠合的双环酸酐中间体，经过五步反应将其转化为带有芳香环的乙烯基内酯-缩醛。接着进行芳基碘化反应，然后与三烷基格氏试剂进行镁-卤交换反应，接着进行分子内环化反应。随后的氧化反应得到所需的 6-7-6 三环二酮醛，三个位置均带有羰基，可进一步进行 C-N 键形成和后续的衍生化反应。
