Enantiopure <i>N</i>-Acyldihydropyridones as Synthetic Intermediates: Asymmetric Synthesis of (−)-Septicine and (−)-Tylophorine
作者:Daniel L. Comins、Xinghai Chen、Lawrence A. Morgan
DOI:10.1021/jo9711495
日期:1997.10.1
A concise asymmetric synthesis of (-)-septicine (1) and (-)-tylophorine (2) was accomplished with a high degree of stereocontrol in eight and nine steps, respectively. Addition of 4-(1-butenyl)magnesium bromide to 1-acylpyridinium salt 3, prepared in situ from 4-methoxy-3-(triisopropylsilyl)pyridine and the chloroformate of (-)-trans-2-(alpha-cumyl)cyclohexanol, gave a 91% yield of diastereomerically
(-)-败血碱(1)和(-)-酪氨酸(2)的简明不对称合成分别通过高度立体控制分别在八个和九个步骤中完成。将4-(1-丁烯基)溴化镁加到1-酰基吡啶鎓盐3中,该盐由4-甲氧基-3-(三异丙基甲硅烷基)吡啶和(-)-反式-2-(α-枯基)环己醇的氯甲酸酯原位制备,得到91%的非对映体纯的二氢吡啶酮7。7的氧化裂解和随后的还原提供了81%产率的醇6。将6转化为氯化物,然后用甲醇钠处理,以高收率得到吲哚并吲哚酮9。用L-Selectride溴化和共轭还原9,并用N-(5-氯-2-吡啶基)三氟甲酰亚胺捕集中间体烯醇化物,得到三氟甲磺酸溴乙烯酯11。过量的钯催化交叉偶联(3,用4-二甲氧基苯基)溴化锌和11得到(-)-败血症(1)。在此综合的基础上,为(-)-1分配了Rconfiguration。1与三氟化钒(V)在TFA / CH(2)Cl(2)中的反应进行氧化偶合,得到68%的(-)-酪氨酸(2)收率。