期刊
CHEMISTRY-AN ASIAN JOURNAL
卷 8, 期 7, 页码 1428-1435出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/asia.201300362
关键词
glycosylation; heterocycles; natural products; polygalolides; total synthesis
资金
- Japan Society for the Promotion of Science (JSPS)
- MEXT
- Suntory Institute for Bioorganic Research
- Daiko Foundation
- Nagoya University
- Grants-in-Aid for Scientific Research [23102015, 24580161] Funding Source: KAKEN
The total synthesis of polygalolideA, a secondary metabolite that was isolated from a Chinese medicinal plant, is reported. A key issue in this synthesis was construction of an oxabicyclo[3.2.1] skeleton, which was solved by the development of an intramolecular Ferrier-type C-glycosylation of a glucal with siloxyfuran as an internal nucleophile. The substrate was prepared from D-glucal by the introduction of trimethylsilylacetylene and siloxyfuran groups. Although C-glycosylation did not occur under the conditions found from model experiments, further examination revealed that the combination of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and 2,4,6-collidine successfully afforded the desired product as a single diastereomer. The siloxy group at the C3 position played a crucial role in the stereocontrol of this reaction. The product was further transformed into a tetracyclic compound as follows: The vinyl ether and acetylenic moieties were reduced and the siloxy group was removed with a Barton-McCombie reaction. The construction of the six-membered ether and the -lactone provided the tetracyclic compound. Finally, a phenolic moiety was introduced by using a Mukaiyama aldol reaction to furnish polygalolideA.
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