Density functional theory calculations and experimental parameters for mutarotation of 6-deoxy-l-mannopyranosyl hydrazine |
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Authors: | Mabel Fragoso-Serrano,Carlos M. Cerda-Garcí a-Rojas |
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Affiliation: | a Departamento de Farmacia, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico City 04510, Mexico b Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, Mexico City 07000, Mexico |
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Abstract: | The geometry and energy profiles of the mutarotation pathway present in the equilibrium of 6-deoxy-β-l-mannopyranosyl 2,4-dinitrophenylhydrazine (1a), 6-deoxy-l-mannose 2,4-dinitrophenylhydrazone (1b), and 6-deoxy-α-l-mannopyranosyl 2,4-dinitrophenylhydrazine (1c) were modeled by DFT calculations at B3LYP/6-31G(d) level affording ΔGDFT=0.000 kcal/mol, ΔGDFT=0.174 kcal/mol, and ΔGDFT=3.411 kcal/mol, respectively. Experimentally, the β-l-pyranose 1a occurs in 50% followed by the acyclic structure 1b in 44% as well as by the α-l-anomer 1c in 6%. The conformations of 1a-c and their corresponding 2,3,4-triacetyl derivatives 2a-c were studied by molecular modeling and NMR spectroscopy. IR frequencies, NMR chemical shifts, and X-ray diffraction analysis were employed to compare theoretical with experimental structural parameters. |
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Keywords: | Glycosylhydrazines Mutarotation DFT calculations NMR X-ray analysis |
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