Intramolecular 1,8- versus 1,6-Hydrogen Atom Transfer between Pyranose Units in a (14)-Disaccharide Model Promoted by Alkoxyl Radical

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• 作者：Angeles Martí ; n ; Iné ; s Pé ; rez-Martí ; n ; Luis M. Quintanal ; Ernesto Su&aacute ; rez
• 刊名：Organic Letters
• 出版年：2007
• 出版时间：April 26, 2007
• 年：2007
• 卷：9
• 期：9
• 页码：1785 - 1788
• 全文大小：86K
• 年卷期：v.9,no.9(April 26, 2007)
• ISSN：1523-7052

文摘

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The stereochemical and conformational factors controlling the intramolecular hydrogen atom transfer (HAT) reaction between the two pyranoseunits in a (1mages/entities/rarr.gif">4)-disaccharide when promoted by a primary 6-O-yl radical are studied. Models with mages/gifchars/alpha.gif" BORDER=0>-D-Glcp-(1mages/entities/rarr.gif">4)-mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-D-Glcp or mages/gifchars/alpha.gif" BORDER=0>-L-Rhamp-(1mages/entities/rarr.gif">4)-mages/gifchars/alpha.gif" BORDER=0>-D-Galp skeletons lead exclusively to the abstraction of H-C-5' and the formation, through a nine-membered transition state, of a1,3,5-trioxocane ring system in a stable boat-chair conformation. Notwithstanding, derivatives of mages/gifchars/alpha.gif" BORDER=0>-L-Rhamp-(1mages/entities/rarr.gif">4)-mages/gifchars/alpha.gif" BORDER=0>-D-Glcp abstract exclusivelyH-C-1' through a seven-membered transition state and therefore lead to an interglycosidic spiro ortho ester.