Total synthesis of (R)-tylophorine by using an asymmetric hydrogenation of the allyl alcohol |
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Authors: | Rui Li Chun-Fang Liu Chun-Jiao Yu Peiming Gu |
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Institution: | College of Chemistry & Chemical Engineering, Ningxia Engineering and Research Center for Natural Medicines, Ningxia University, Yinchuan 750021, China |
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Abstract: | An efficient synthesis of naturally occurring (R)-tylophorine is described. The alkaloid was prepared in seven steps from a known phenanthryl aldehyde with an overall yield of 14.2%. Asymmetric hydrogenation of an allyl alcohol was employed as a key step for installing a stereogenic center with good enantioselectivity (77% ee), and the ee value of the ω-chloro alcohol was improved to 95% by recrystallization. After azidation and oxidation of the enantio-enriched ω-chloro alcohol to the precursor of the Schmidt reaction, the chirality transfer in the stereospecific 1,2-migration furnished the chiral carbon in the alkaloid. Finally, a one-pot deformylation/Pictet-Spengler cyclization completed the total synthesis of (R)-tylophorine. |
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Keywords: | Tylophorine Total synthesis Asymmetric hydrogenation Schmidt reaction |
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