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Titre du document / Document title

DFT study of α-and β-D-allopyranose at the B3LYP/6-311++G** level of theory

Auteur(s) / Author(s)

SCHNUPF Udo ; WILLETT J. L. ; BOSMA Wayne B. ; MOMANY Frank A. ;

Résumé / Abstract

One hundred and two conformations of α- and β-D-allopyranose, the C-3 substituted epimer of glucopyranose, were geometry optimized using the density functional, B3LYP, and the basis set, 6-311++G**. Full geometry optimization was performed on different ring geometries and on the hydroxymethyl rotamers (gg/gt/tg). Analytically derived Hessians were used to calculate zero point energy, enthalpy, and entropy. The lowest energy and free energy conformation found is the α-tg(g-)-4C1-c conformation, which is only slightly higher in electronic (∼0.2 kcal/mol) and free energy than the lowest energy α-D-glucopyranose. The in vacuo calculations showed a small (∼0.3 kcal/mol) energetic preference for the α- over the β-anomer for allopyranose in the 4C1 conformation, whereas in the 1C4 conformation a considerable (∼1.6 kcal/mol) energetic preference for the β- over the α-anomer for allopyranose was encountered. The results are compared to previous aldohexose calculations in vacuo. Boat and skew forms were found that remained stable upon gradient optimization although many starting boat conformations moved to other skew forms upon optimization. As found for glucose, mannose, and galactose the orientation and interaction of the hydroxyl groups make the most significant contributions to the conformation/energy relationship in vacuo. A comparison of different basis sets and density functionals is made in the Discussion section, confirming the appropriateness of the level of theory used here.

Revue / Journal Title

Carbohydrate research    ISSN  0008-6215   CODEN CRBRAT 

Source / Source

2007, vol. 342, no2, pp. 196-216 [21 page(s) (article)]

Langue / Language

Anglais

Editeur / Publisher

Elsevier, Oxford, ROYAUME-UNI  (1965) (Revue)

Mots-clés d'auteur / Author Keywords

B3LYP/6-311++G**

;

Allose

;

Chair

;

Boat

;

Skew

;

Conformation

;

Hessian

;

Relative free energy

;

Localisation / Location

INIST-CNRS, Cote INIST : 12339, 35400015933170.0070

Nº notice refdoc (ud4) : 18458948



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