First author et al.
Report
Scheme 5. Synthesis of diosgenin trisaccharides 17 and 33 by a three-component, “one-pot” glycosylation.
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Conclusions
In summary, we have reported a new approach for the
synthesis of polyphyllin D (
1) and its natural and synthetic
congeners ( ), featuring the use of the gold(I)-catalyzed
2-5
glycosylation with ortho-alkynylbenzoates as donors. The
current approach highlights the following: (i) The use of one
type of donors that warranted use of a single promoter
(PPh3AuOTf) at every stage of the glycosylation; and (ii) the
loading of the gold(I) catalyst could be greatly reduced (from
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the conventional
10 mol% to 0.5 mol%) with the
co-catalysis of HOTf, In(OTf)3, or Ga(OTf)3 (5-20 mol%). While
the findings from this work suggest that a Lewis acid could
facilitate the regeneration of the catalytic Au(I) species,
mechanistic investigation of this co-catalysis is a subject of
our future research, so are the biological profiles of the
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Experimental
(Main Text Paragraphs) Please include all the experimental
details here excluding those in Supporting Information.
Supporting Information
The supporting information for this article is available on the
Acknowledgement
Financial support from National Natural Science Foundation of
China (21432012, 21621002 and 21602240), Strategic Priority
Research Program of CAS (XDB20020000), and K. C. Wong
Education Foundation is acknowledged. T.S.E is grateful to the
Chinese Scholarship Council (CSC) for a scholarship to undertake
the doctoral studies.
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