A Tandem Horner−Emmons Olefination−Conjugate Addition Approach to the Synthesis of 1,5-Disubstituted-6-azabicyclo[3.2.1]octanes Based on the AE Ring Structure of the Norditerpenoid Alkaloid Methyllycaconitine
作者:David J. Callis、Noel F. Thomas、David P. J. Pearson、Barry V. L. Potter
DOI:10.1021/jo9519672
日期:1996.1.1
A novel Horner-Emmons olefination conjugate addition reaction of N-acetylamides to form 1,5-disubstituted-6-azabicyclo[3.2.1]octanes with two bridgehead quarternary carbon centers is reported. This reaction is a key step in an approach to the synthesis of small ring analogues based on the AE ring structure of the Delphinium norditerpenoid, methyllycaconitine (MLA) (1). Initially, 3-(hydroxymethyl)cyclohex-2-en-1-one
报道了一种新颖的N-乙酰酰胺的霍纳-埃蒙斯烯化共轭加成反应,形成带有两个桥头四元碳中心的1,5-二取代-6-氮杂双环[3.2.1]辛烷。该反应是基于Delphinium norditerpenoidoid,甲基lycaconitine(MLA)的AE环结构合成小环类似物的关键步骤。最初,选择3-(羟甲基)环己基-2-烯-1-酮(10)作为这些结构的起始材料,但事实证明生成效率低下。相反,3-[((苯硫基)甲基]环己-2-烯-1-酮(6)和3-(1,3-二噻-2--2-基)环己-2-烯-1-酮( 11)收成良好。随后进行氢氰化,缩酮化,还原,乙酰化,缩醛脱保护,和霍纳-埃蒙斯烯烃共轭加成反应形成1-[((苯硫基)甲基] -5-[(乙氧羰基)甲基] -6-乙酰氨基-6-氮杂双环[3.2.1]辛烷(28),1-(1分别报道了,3-二噻二-2-基)-5-[(乙氧羰基)甲基] -6-乙酰基-6-氮杂双环[3