enantioselective total synthesis of (-)-strychnine was accomplished through the use of the highly practical catalytic asymmetricMichael reaction (0.1 mol % of (R)-ALB, more than kilogram scale, without chromatography, 91% yield and >99% ee) as well as a tandem cyclization that simultaneously constructed B- and D-rings (>77% yield). Moreover, newly developed reaction conditions for thionium ion cyclization, NaBH3CN
(-)-士的宁的对映选择性全合成是通过使用高度实用的催化不对称迈克尔反应(0.1 mol % (R)-ALB,超过千克规模,无需色谱,91%产率和>99%ee)完成的) 以及同时构建 B 环和 D 环的串联环化(> 77% 产率)。此外,新开发的硫鎓离子环化反应条件、在路易斯酸存在下亚胺部分的 NaBH3CN 还原以防止开环反应以及在环外烯烃存在下硫醚的化学选择性还原(脱硫)对于完成合成至关重要. 所描述的化学反应为合成更先进的马钱子生物碱铺平了道路。
Enantioselective total synthesis of (−)-strychnine: development of a highly practical catalytic asymmetric carbon–carbon bond formation and domino cyclization
An enantioselective totalsynthesis of (−)-strychnine was accomplished through the use of the highly practical catalyticasymmetricMichaelreaction (0.1 mol% of (R)-ALB, greater than kilogram scale, without chromatography, 91% yield and >99% ee), and a domino cyclization that simultaneously constructed the B- and D- rings of strychnine (>77% yield). Newly-developed reaction conditions for thionium