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The exocyclic hydroxymethyl group of the -D-1-amino-1-deoxyglucopyranose can rotate around the carbon-carbon bond. Potential energy surface for this rotation has been investigated using ab initio quantum chemical methods. Relevant stationary points, including for the first time rotational transition states have been characterized by full geometry optimization using basis sets 6-31G(d) and 6-31G(2d,lp). There is a total of six stationary points along the hydroxymethyl rotational surface, including three minima and three transition states were identified. The effects of basis set augmentation and electron correlation on the relative energies are small; the relative energies for each stationary point vary by less than 2.5 kJ/mol for all levels of theory considered. The final barriers to hydroxymethyl rotation ranged from 15 to 41 kJ/mol. | Journal of Chemistry Vol. 42 3 P. 388 - 391 2004 THE MOLECULAR CONFORMATIONS OF a-D-1-AMINO-1-DEOXYGLUCOPYRANOSE Received 27-9-2003 NGUyEN DINH THANH Faculty of Chemistry University of Natural Sciences Hanoi National University SUMMARY The exocyclic hydroxymethyl group of the a-D-1 -amino-1 -deoxyglucopyranose can rotate around the carbon-carbon bond. Potential energy surface for this rotation has been investigated using ab initio quantum chemical methods. Relevant stationary points including for the first time rotational transition states have been characterized by full geometry optimization using basis sets 6-31G d and 6-31G 2d lp . There is a total of six stationary points along the hydroxymethyl rotational surface including three minima and three transition states were identified. The effects of basis set augmentation and electron correlation on the relative energies are small the relative energies for each stationary point vary by less than 2.5 kJ mol for all levels of theory considered. The final barriers to hydroxymethyl rotation ranged from 15 to 41 kJ mol. I - INTRODUCTION Some compounds containing a-D-glucosyl-amine i.e. a-D-1-amino-1-deoxygluco-pyranose were found in the nature. For example the glucosylamines of procainamide and the pharmacokinetics of the betaglucosylamine of procainamide in the conscious rabbit were evaluated 1 . It is similar in a-D-2-amino-2-deoxyglucopyranose a particularly critical region of the glucopyranose conformational surface relates to rotation of the exocyclic hydroxymethyl group 3 4 . Three minimum conformations were found along the exocyclic hydroxymethyl rotational surface designated GG gauche gauche GT gauche trans and TG trans gauche each separated by approximately 120o dihedral rotation. The relative energy differences between conformers of was small 4 kJ mol and somewhat basic set dependent 5 . Continuing the previous articles about a-and P-2-amino-2-deoxyglucopyranoses 3 4 388 this work reports ab initio quantum .