Total Syntheses of Murrayamine E, I, and K

We describe efficient synthetic routes to murrayamine A (mukoenine C), O-methylmurrayamine A, mahanine, O-methylmahanine, and murrayamine D and the first total syntheses of murrayamine E, I, and K. Key steps are a palladium-catalyzed construction of the carbazole framework and an annulation of the pyran ring, which is either catalyzed by phenylboronic acid or promoted by a Lewis acid.本研究报道了山小橘碱A（murrayamine A，别名穆柯宁C（mukoenine C））、O-甲基山小橘碱A（O-methylmurrayamine A）、麻榔碱（mahanine）、O-甲基麻榔碱（O-methylmahanine）以及山小橘碱D（murrayamine D）的高效合成路线，同时首次实现了山小橘碱E（murrayamine E）、山小橘碱I（murrayamine I）与山小橘碱K（murrayamine K）的全合成。核心反应步骤包括钯催化构建咔唑骨架（carbazole framework），以及分别以苯硼酸（phenylboronic acid）催化或路易斯酸（Lewis acid）促进的吡喃环（pyran ring）环化反应。