2018年4月3日火曜日

Aryl C-Glycoside via Fe Coupling 2017


https://pubs.acs.org/doi/abs/10.1021/jacs.7b03867


http://www.kuicr.kyoto-u.ac.jp/sites/topics/171213/




Article




Synthesis of Aryl C-Glycosides via Iron-Catalyzed Cross Coupling of Halosugars: Stereoselective Anomeric Arylation of Glycosyl Radicals

International Research Center for Elements Science, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan
§ Department of Chemistry and Center of Novel Functional Molecules, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
Department of Applied Chemistry, Okayama University of Science, Ridai-cho, Okayama 700-0005, Japan
J. Am. Chem. Soc., 2017, 139 (31), pp 10693–10701
DOI: 10.1021/jacs.7b03867
Publication Date (Web): August 1, 2017
Copyright © 2017 American Chemical Society

Abstract

Abstract Image
We have developed a novel diastereoselective iron-catalyzed cross-coupling reaction of various glycosyl halides with aryl metal reagents for the efficient synthesis of aryl C-glycosides, which are of significant pharmaceutical interest due to their biological activities and resistance toward metabolic degradation. A variety of aryl, heteroaryl, and vinyl metal reagents can be cross-coupled with glycosyl halides in high yields in the presence of a well-defined iron complex, composed of iron(II) chloride and a bulky bisphosphine ligand, TMS-SciOPP. The chemoselective nature of the reaction allows the use of synthetically versatile acetyl-protected glycosyl donors and the incorporation of various functional groups on the aryl moieties, producing a diverse array of aryl C-glycosides, including Canagliflozin, an inhibitor of sodium-glucose cotransporter 2 (SGLT2), and a prevailing diabetes drug. The cross-coupling reaction proceeds via generation and stereoselective trapping of glycosyl radical intermediates, representing a rare example of highly stereoselective carbon–carbon bond formation based on iron catalysis. Radical probe experiments using 3,4,6-tri-O-acetyl-2-O-allyl-α-d-glucopyranosyl bromide (8) and 6-bromo-1-hexene (10) confirm the generation and intermediacy of the corresponding glycosyl radicals. Density functional theory (DFT) calculations reveal that the observed anomeric diastereoselectivity is attributable to the relative stability of the conformers of glycosyl radical intermediates. The present cross-coupling reaction demonstrates the potential of iron-catalyzed stereo- and chemoselective carbon–carbon bond formation in the synthesis of bioactive compounds of certain structural complexity.
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.7b03867.
  • Experimental details, procedures, compound characterization data, NMR spectra, and X-ray crystallographic data (PDF)
  • Crystallographic data (CIF, CIF)
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Received 18 April 2017
Published online 1 August 2017
Published in print 9 August 2017
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