easier to work up. An enantiospecific total synthesis of (+)-polyneuridine aldehyde (6), which has been proposed as an important biogenetic intermediate in the biosynthesis of quebrachidine (2), was then accomplished in an overall yield of 14.1% in 13 reaction vessels from d-(+)-tryptophan methyl ester (14). Aldehyde 13 was protected as the Na-Boc aldehyde 32 and then converted into the prochiral C(16)-quaternary
聚神经
氨酸醛 ( 6 )、16-epivellosimine ( 7 )、(+)-聚神经
氨酸 ( 8 ) 和 (+)-macusine A ( 9 )的首次立体有择合成已从市售的d -(+)-色
氨酸中完成甲酯。d -(+)-色
氨酸在这里既用作手性助剂又用作合成常见中间体 (+)-velosimine ( 13 )的起始材料。这种
生物碱可在七个反应容器中以对映特异性方式获得,d -(+)-色
氨酸甲酯的总产率为 27% ( 14) 通过不对称 Pictet-Spengler 反应、Dieckmann 环化和立体控制的分子内烯醇驱动的
钯介导的交叉偶联反应的组合。已经通过
铜介导的过程开发了这种立体控制的分子内交叉偶联的新过程。这项研究的初步结果表明,烯醇驱动的
钯介导的交叉偶联反应可以通过
铜介导的过程完成,该过程更便宜且更容易处理。的对映体特异性合成总(+) - polyneuridine醛(6),