- Asymmetric Total Synthesis of Sarpagine and Koumine Alkaloids
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We report here a concise, collective, and asymmetric total synthesis of sarpagine alkaloids and biogenetically related koumine alkaloids, which structurally feature a rigid cage scaffold, with L-tryptophan as the starting material. Two key bridged skeleton-forming reactions, namely tandem sequential oxidative cyclopropanol ring-opening cyclization and ketone α-allenylation, ensure concurrent assembly of the caged sarpagine scaffold and installation of requisite derivative handles. With a common caged intermediate as the branch point, by taking advantage of ketone and allene groups therein, total synthesis of five sarpagine alkaloids (affinisine, normacusine B, trinervine, Na-methyl-16-epipericyclivine, and vellosimine) with various substituents and three koumine alkaloids (koumine, koumimine, and N-demethylkoumine) with more complex cage scaffolds has been accomplished.
- He, Ling,Jiang, Yan,Qiao, Zhen,Qiu, Hanyue,Su, Xiaojiao,Tan, Qiuyuan,Yang, Jiaojiao,Yang, Zhao,Zhang, Min,Zhou, Wenqiang
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p. 13105 - 13111
(2021/05/10)
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- The enantiospecific, stereospecific total synthesis of the ring-A oxygenated sarpagine indole alkaloids (+)-majvinine, (+)-10-methoxyaffinisine, and (+)-Na-methylsarpagine, as well as the total synthesis of the Alstonia bisindole alkaloid macralstonidine
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The first stereospecific, enantiospecific total synthesis of the ring-A oxygenated sarpagine indole alkaloids (+)-Na-methylsarpagine (8), (+)-majvinine (14), and (+)-10-methoxyaffinisine (49), as well as the first total synthesis of the Alstonia bisindole alkaloid macralstonidine (9), has been accomplished. This approach employed the Schoellkopf chiral auxiliary for the stereospecific construction of the desired D-(+)-tryptophan unit required for the asymmetric Pictet-Spengler reaction. In addition, the strategy was doubly convergent for the enolate-mediated Pd0 coupling process and the asymmetric Pictet-Spengler reaction can be employed to synthesize both macroline (2) and Na-methylsarpagine (8), the coupling of which provides macralstonidine (9). This approach to ring-A substituted alkoxyindole alkaloids should find wide application for the synthesis of other alkaloids for it is stereospecific and either enantiomer can be prepared with ease.
- Zhao, Shuo,Liao, Xuebin,Wang, Tao,Flippen-Anderson, Judith,Cook, James M.
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p. 6279 - 6295
(2007/10/03)
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