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Volumn , Issue 27, 2010, Pages 5248-5262

Hydrogen atom transfer experiments provide chemical evidence for the conformational differences between C-and O-disaccharides

Author keywords

Carbohydrates; Conformation analysis; Disaccharides; Hydrogen transfer; Radical reactions

Indexed keywords


EID: 77956475818     PISSN: 1434193X     EISSN: 10990690     Source Type: Journal    
DOI: 10.1002/ejoc.201000470     Document Type: Article
Times cited : (11)

References (84)
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    • For other references on HAT reaction in disaccharide systems, see: a
    • For other references on HAT reaction in disaccharide systems, see: a) A. Martín, I. Pérez-Martín, L. M. Quintanal, E. Suárez, Org. Lett. 2007, 9, 1785-1788;
    • (2007) Org. Lett. , vol.9 , pp. 1785-1788
    • Martín, A.1    Pérez-Martín, I.2    Quintanal, L.M.3    Suárez, E.4
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    • 3, Schrödinger, LLC, New York, NY, 2009. The minimum for each conformational isomer was calculated performing a coordinate scan calculation of Φ and Ψ dihedrals from-180 to 180° in increments of 5°. See the corresponding contour plots at the Supporting Information section
    • 3, Schrödinger, LLC, New York, NY, 2009. The minimum for each conformational isomer was calculated performing a coordinate scan calculation of Φ and Ψ dihedrals from-180 to 180° in increments of 5°. See the corresponding contour plots at the Supporting Information section.
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    • The methoxy groups at C-2′ and C-3 were easily distinguished by 2D HSQC and HMBC correlations
    • The methoxy groups at C-2′ and C-3 were easily distinguished by 2D HSQC and HMBC correlations.
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    • As expected, the preferred conformation of the rings is determined principally by the maximum number of anomeric effects a, Pergamon Press, New York
    • As expected, the preferred conformation of the rings is determined principally by the maximum number of anomeric effects a) P. Deslongchamps, Stereoelectronic Effects in Organic Chemistry, Pergamon Press, New York, 1983;
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    • Using a modified Karplus-type calculation as implemented in Maestro, version 9.0, Schrödinger, LLC, New York, NY
    • Using a modified Karplus-type calculation as implemented in Maestro, version 9.0, Schrödinger, LLC, New York, NY, 2009.
    • (2009)
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    • Details on the preparation of these models are provided in the Supporting Information section
    • Details on the preparation of these models are provided in the Supporting Information section.
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    • A part of the present work has been published as a preliminary communication
    • A part of the present work has been published as a preliminary communication: A. Martín, L. M. Quintanal, E. Suárez, Tetrahedron Lett. 2007, 48, 5507-5511.
    • (2007) Tetrahedron. Lett. , vol.48 , pp. 5507-5511
    • Martín, A.1    Quintanal, L.M.2    Suárez, E.3
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    • For convenience, the atom-numbering system used throughout this section and in the NMR assignments is the one depicted in the corresponding Scheme although a IUPAC systematic nomenclature has been used in the Experimental and Supporting Information sections
    • For convenience, the atom-numbering system used throughout this section and in the NMR assignments is the one depicted in the corresponding Scheme although a IUPAC systematic nomenclature has been used in the Experimental and Supporting Information sections.
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    • 13J C1, H1 coupling constants and intramolecular NOE experiments, and references cited therein
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    • The high propensity of mannopyranosyl radicals for quenching by stannanes along the axial direction and formation of equatorial glycosides is well established. See, for example:, and references cited therein
    • The high propensity of mannopyranosyl radicals for quenching by stannanes along the axial direction and formation of equatorial glycosides is well established. See, for example: D. Crich, S. Sun, J. Brunckova, J. Org. Chem. 1996, 61, 605-615 and references cited therein.
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    • For studies on stereoelectronic effects in intermolecular hydrogen abstraction reactions see: a
    • For studies on stereoelectronic effects in intermolecular hydrogen abstraction reactions see: a) V. Malatesta, K. U. Ingold, J. Am. Chem. Soc. 1981, 103, 609-614;
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    • Radical-mediated intermolecular brominations can discriminate between H-5′ and H-1′, but the regioselectivity of the reaction is largely dependent on the anomeric substituent and configuration, as well as the halogenating agent used. In consequence, the regioselectivity results observed in these intermolecular reactions are not easily extrapolated to our models. In fact, a closely related compound, methyl 2, 3, 4, 6-tetra-O-acetyl-α-D- mannopyranoside, does not give any bromination and most of it was recovered unchanged after prolonged reaction times a
    • Radical-mediated intermolecular brominations can discriminate between H-5′ and H-1′, but the regioselectivity of the reaction is largely dependent on the anomeric substituent and configuration, as well as the halogenating agent used. In consequence, the regioselectivity results observed in these intermolecular reactions are not easily extrapolated to our models. In fact, a closely related compound, methyl 2, 3, 4, 6-tetra-O-acetyl-α-D- mannopyranoside, does not give any bromination and most of it was recovered unchanged after prolonged reaction times a) L. Somsák, R. J. Ferrier, Adv. Carbohyd. Chem. Biochem. 2000, 56, 65-151;
    • (2000) Adv. Carbohyd. Chem. Biochem. , vol.56 , pp. 65-151
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    • 1,5-HAT is by far the most common intramolecular reaction when promoted by an alkoxy radical. However, examples of 1,6-hydrogen transfer through a seven-membered transition state from reactive carbons have also been described, high yields only being obtained in those cases when the hydrogen to be abstracted is bonded to an oxygen-substituted carbon: a, in:, Eds.: P. Renaud, M. P. Sibi, Wiley-VCH, Weinheim
    • 1,5-HAT is by far the most common intramolecular reaction when promoted by an alkoxy radical. However, examples of 1,6-hydrogen transfer (through a seven-membered transition state) from reactive carbons have also been described, high yields only being obtained in those cases when the hydrogen to be abstracted is bonded to an oxygen-substituted carbon: a) L. Feray, N. Kuznetsov, P. Renaud, in: Radicals in Organic Synthesis, Vol. 2 (Eds.: P. Renaud, M. P. Sibi), Wiley-VCH, Weinheim, 2001, pp. 246-278;
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    • Feray, L.1    Kuznetsov, N.2    Renaud, P.3
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* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.