Triconoids A–D, Four Limonoids Possess Two Rearranged Carbon Skeletons from Trichilia connaroides

Four limonoids, triconoids A–C (1–3) possessing a new rearranged mexicanolide skeleton and triconoid D (4) furnishing a new rearranged 1,2-seco-phragmalin skeleton, were isolated from the Nepalese plant Trichilia connaroides. Two rearranged limonoid skeletons sharing an F ring of methyl 5-oxotetrahydrofuran-2-carboxylate were postulated to be formed biosynthetically via a very unique chemical cascade. Their structures were fully accomplished by spectroscopic data, single-crystal X-ray diffraction, and electrostatic circular dichroism analysis.本研究从尼泊尔产毛叶溪桫（Trichilia connaroides）中分离得到4个柠檬苦素类化合物（limonoids）：其中锥果素A–C（triconoids A–C，1–3号）具有全新重排的墨西哥苦内酯型（mexicanolide）骨架，锥果素D（triconoid D，4号）则拥有全新重排的1,2-开环印梀苦内酯型（1,2-seco-phragmalin）骨架。两类共享5-氧代四氢呋喃-2-羧酸甲酯（methyl 5-oxotetrahydrofuran-2-carboxylate）F环的重排柠檬苦素类骨架，被推测通过一种极为独特的化学级联反应完成生物合成。所有化合物的结构均通过光谱数据、单晶X射线衍射（single-crystal X-ray diffraction）以及静电圆二色谱（electrostatic circular dichroism）分析得到完整确证。