Synthesis of Highly Oxidized Quinolizidine via Reduction of Acylpyridinium Cations

提出了一种以酰基吡啶阳离子为还原环化反应合成喹诺利定骨架的新方法。在温和的反应条件下，几个官能团是可以容忍的。该反应被成功地扩展到一锅法合成双环化合物，新方法已应用于用顺式-顺式立体化学立体选择性地构筑具有顺式-顺式立体化学的苦参碱类生物碱的喹诺利定骨架的AB环。该方法的主要特点包括：(I)通过还原酰基吡啶阳离子来构建喹诺利定；(Ii)通过顺序的Stille偶联和非对映选择性氢化反应来晚期引入甲氧基吡啶。

A new strategy for synthesizing quinolizidine skeletons by reductive cyclization via acylpyridinium cations was developed. Several functional groups were tolerated under mild reaction conditions. The reaction was successfully extended to a one-pot synthesis of a bicyclic compound.The new method has been applied to the stereoselective construction of the AB rings of the quinolizidine skeleton of sophoramine-type alkaloids with a cis-cis stereochemistry. The key features of this method involve: (i) the construction of the quinolizidine by the reduction of an acylpyridinium cation; and (ii) the late stage introduction of methoxypyridine by sequential Stille coupling and diastereoselective hydrogenation reactions.