Sun Hao, Yu Cheng-Long, Zheng Yu-Qing, Shu Peng-Fei, Dong Zhan, Xia Yu-Chen, Liu Wen-Bo
Hubei Research Center of Fundamental Science-Chemistry, Engineering Research Center of Organosilicon Compounds & Materials, Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, and College of Chemistry and Molecular Sciences, Wuhan University 299 Bayi Rd Wuhan 430072 China
State Key Laboratory of Virology and Hubei Province Key Laboratory of Allergy and Immunology, Institute of Medical Virology, TaiKang Medical School, Wuhan University 299 Bayi Rd Wuhan 430072 China.
Chem Sci. 2025 Mar 10;16(15):6425-6433. doi: 10.1039/d4sc08215j. eCollection 2025 Apr 9.
The hydrocarbazole scaffold represents the core structure of numerous monoterpenoid indole alkaloids. The development of catalytic methods that provide efficient access to enantioenriched hydrocarbazole derivatives is central for the synthesis of these bioactive alkaloids. We report here a palladium-catalyzed enantioselective formal 5- arylative cyclization of enaminones, facilitating the construction of hexahydrocarbazol-4-ones containing contiguous C4a-quaternary and C9a-tertiary stereocenters with high enantioselectivities (86.5 : 13.5-99 : 1 er) and diastereoselectivities (>20 : 1 dr). Notably, enaminone substrates bearing an α-allyl group undertake an arylation/Cope rearrangement cascade, offering a unique route to C1-substituted tetrahydrocarbazol-4-ones. A stereodivergent approach to all four stereoisomers of the quaternary/tertiary chiral center set is achieved by combining the catalyst with / allyl substituents, yielding excellent enantioselectivity. The -methyl group of the hydrocarbazolone products is readily removed under oxidation conditions. The utility of the method is demonstrated by the access to a variety of hydrocarbazole derivatives and the efficient syntheses of four alkaloids/analogs, (+)--methyl aspidospermidine, (+)-C20--methyl aspidospermidine, (+)--methyl fendleridine, and (+)--methyl limaspermidine from a hexahydrocarbazol-4-one in 3-5 steps.
氢化咔唑骨架是众多单萜吲哚生物碱的核心结构。开发能够有效获得对映体富集的氢化咔唑衍生物的催化方法对于这些生物活性生物碱的合成至关重要。我们在此报告一种钯催化的烯胺酮对映选择性形式5-芳基化环化反应,该反应有助于构建含有相邻C4a-季碳和C9a-叔碳立体中心的六氢咔唑-4-酮,具有高对映选择性(对映体比例为86.5∶13.5至99∶1)和非对映选择性(非对映体比例>20∶1)。值得注意的是,带有α-烯丙基的烯胺酮底物会发生芳基化/Cope重排级联反应,为C1-取代的四氢咔唑-4-酮提供了一条独特的合成路线。通过将催化剂与烯丙基取代基相结合,实现了对季碳/叔碳手性中心所有四种立体异构体的立体发散合成方法,产生了优异的对映选择性。氢化咔唑酮产物的甲基在氧化条件下很容易被去除。该方法的实用性通过获得多种氢化咔唑衍生物以及从六氢咔唑-4-酮经3至5步高效合成四种生物碱/类似物,即(+)-N-甲基阿斯品多灵、(+)-C20-N-甲基阿斯品多灵、(+)-N-甲基芬德里定和(+)-N-甲基利马斯品定得到了证明。