Synthesis of Highly Oxidized Quinolizidine via Reduction of Acylpyridinium Cations

提出了一种通过酰基吡啶阳离子还原环化合成喹里嗪骨架的新方法。在温和的反应条件下，几个官能团是耐受的。该反应已成功地推广到一锅法合成双环化合物，并应用于具有顺-顺立体化学的槐胺型生物碱喹嗪啶骨架AB环的立体选择性构筑。该方法的关键特征包括：（i）通过还原酰基吡啶阳离子构建喹嗪;和（ii）通过顺序的Stille偶联和非对映选择性氢化反应后期引入甲氧基吡啶。

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.