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Alcohols, ethers, carbohydrates, and related compounds. IV. carbohydrates
Author(s) -
Lii JennHuei,
Chen KuoHsiang,
Allinger Norman L.
Publication year - 2003
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.10271
Subject(s) - pyranose , furanose , chemistry , anomer , anomeric effect , computational chemistry , ab initio , molecule , basis set , carbohydrate , ab initio quantum chemistry methods , hydrogen bond , force field (fiction) , crystallography , stereochemistry , organic chemistry , density functional theory , ring (chemistry) , artificial intelligence , computer science
Ab initio calculations [B3LYP/6‐311++G(2d,2p)] have been carried out on 84 conformations of 12 different sugars (hexoses), in both pyranose and furanose forms, with the idea of generating a data base for carbohydrate structural energies that may be used for developing the predictive value of molecular mechanics calculations for carbohydrates. The average value for the apparent gas phase anomeric effect for a series of 31 pairs of pyranose conformations was found to be 1.83 kcal/mol (vs. 2.67 kcal/mol with a smaller basis set used in earlier calculations). In developing MM4 to reproduce these data, it was necessary first to have good energies for simple alcohols and ethers, together with an adequate treatment of hydrogen bonding, and then to include the anomeric effect, and the ethylene glycol type system, as was previously recognized. It was also found that the so‐called delta‐2 effect, long recognized in carbohydrates, must be explicitly included, in order to obtain acceptable results. When a force field that included all of these items as developed from the small molecules based on the MM4 hydrocarbon force field was applied without any parameter adjustment to the set of hexopyranose and furanose conformations mentioned earlier, the E β − E α was found to have an average value of 1.88 kcal/mol, versus 1.74 for the quantum calculations. The signed average and RMS deviations of the MM4 from the QM results were +0.15 and 0.87 kcal/mol. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1504–1513, 2003