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On the Generalized Valence Bond Description of the Anomeric and Exo-anomeric Effects: an Ab Initio Conformational Study of 2-Methoxytetrahydropyran by Rodrigo S. Bitzer; André G.H. Barbosa; Clarissa O. da Silva; Marco A.C. Nascimento is a Biochemistry, Genetics and Molecular Biology article available to read on EtoBox.

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An ab initio conformational study of the a-and b-glycosidic C1-O1 bonds has been carried out on the axial and equatorial forms of 2-methoxytetrahydropyran (2-MTHP) at the HF/6-31G(d,p) and GVB-PP/6-31G(d,p) levels of calculation. Six conformers of 2-MTHP were fully optimized at both levels. The calculations have shown that the conformer containing the (+sc) orientation around the axial C1-O1 bond is the most stable one and is favored over that bearing the (Àsc) arrangement about the equatorial C1-O1 bond by 1.39 (HF) and 1.52 (GVB-PP) kcal/mol. The potential energy surfaces for rotating about the axial and equatorial C1-O1 bonds were constructed at the HF and GVB-PP levels. For each form of 2-MTHP the HF and GVB-PP potential curves exhibit similar profiles. This shows that both methods provide similar descriptions for the position of the conformational minima and for the values and location of the rotational barriers. In addition to the conformational study, a discussion concerning the nature of the chemical bond in acetal fragments and the origin of the anomeric and exo-anomeric effects is presented in terms of optimized non-orthogonal GVB orbitals of 2-MTHP. The intramolecular fa

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Author

Rodrigo S. Bitzer; André G.H. Barbosa; Clarissa O. da Silva; Marco A.C. Nascimento

Publisher

Elsevier Science; Elsevier ; Elsevier Ltd.; Elsevier BV (ISSN 0008-6215)

Published

2005

Language

EN

Field

Biochemistry, Genetics and Molecular Biology (Life Sciences)