Total Synthesis of (−)-Dendrobine via α-Carbonyl Radical Cyclization

Autor:	Wei-Hong Tseng, Rei-Torng Chiu, ‡ and Fen-Ling Liao, Sue-Lein Wang, Nai-Tung Yao, Chin-Kang Sha, Cheng-Fen Yang
Rok vydání:	1997
Předmět:	chemistry.chemical_classification Jones oxidation Ketone Trimethylsilyl Acetal Diol General Chemistry Biochemistry Medicinal chemistry Radical cyclization Catalysis chemistry.chemical_compound Colloid and Surface Chemistry chemistry Dendrobine Enol ether
Zdroj:	Journal of the American Chemical Society. 119:4130-4135
ISSN:	1520-5126 0002-7863
DOI:	10.1021/ja9643432
Popis:	An efficient total synthesis of enantiomerically pure (−)-dendrobine (1) is accomplished based on an α-carbonyl radical cyclization reaction. (S)-carvotanacetone (6) was converted to bicyclic acetal-enone 4 in five steps. CuI-mediated conjugate addition of 4-(trimethylsilyl)-3-butynylmagnesium chloride to 4 followed by treatment with TMSCl afforded trimethylsilyl enol ether 10. Iodination of 10 with NaI and m-CPBA gave iodoketone 3. Intramolecular radical cyclization of 3, effected with Bu3SnH and AIBN, furnished tricyclic ketone 2. Removal of the TMS group of 2 and oxidation of the resulting cyclic acetal 12 with m-CPBA and BF3 etherate gave peroxy compound 13. Compound 13 was treated with DBU to yield lactone 14. Hydroboration of 14 with basic H2O2 oxidation gave diol 17. Conversion of 17 to the corresponding azido alcohol 19 followed by Jones oxidation furnished azido ketone 20. Treatment of 20 with PPh3 followed by reduction with NaBH3CN afforded amine 21. Crude amine 21 was methylated to give enantio...
Databáze:	OpenAIRE
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