Synthesis of Isohasubanan Alkaloids via Enantioselective Ketone Allylation and Discovery of an Unexpected Rearrangement
作者:Daniel K. Nielsen、Laura L. Nielsen、Spencer B. Jones、Lawrence Toll、Matthew C. Asplund、Steven L. Castle
DOI:10.1021/jo802370v
日期:2009.2.6
anionic oxy-Cope rearrangement, and acid-promoted cyclization. The final step was thwarted by a pinacol-like rearrangement that delivered the unnatural isohasubanan alkaloid skeleton. The structures of the products were established by exhaustive NMR experiments and confirmed by GIAO 13C NMR calculations of runanine, isorunanine, and three other isomers. These computations revealed some inconsistencies
尝试通过统一的路线合成哈斯巴南生物碱哈斯巴宁碱,符拉宁和aknadinine。通过Suzuki偶联-Wittig烯化-闭环复分解序列构建关键的菲中间体,可实现一种收敛且灵活的方法。菲到目标结构的转化预计涉及六个步骤,包括酚氧化,酮烯丙基化,阴离子氧化-Cope重排和酸促进的环化。最终的步骤因像频哪醇的重排而受阻,这种重排提供了不自然的异哈苏巴南生物碱骨架。产品的结构通过详尽的NMR实验确定,并由GIAO 13确认。牛磺酸,异盐酸尿烷和其他三种异构体的13 C NMR计算。这些计算表明与苯溶剂校正存在一些不一致之处,这表明在使用此算法时应谨慎行事。通过发现Nakamura的手性双恶唑啉连接的烯丙基锌试剂可介导93%ee中的酮19的对映选择性烯丙基化,将异hasubanonine的外消旋合成转变为对映选择性合成。该方法可扩展到其他三个结构相关的酮(92-96%ee),并且完成了另外两种异哈苏巴