途径与群体：5-(羟甲基)四氢吡喃环外扭转的立体电子学见解。
Pathways and populations: stereoelectronic insights into the exocyclic torsion of 5-(hydroxymethyl)tetrahydropyran.
作者信息
Woodcock H Lee, Brooks Bernard R, Pastor Richard W
机构信息
Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
出版信息
J Am Chem Soc. 2008 May 21;130(20):6345-7. doi: 10.1021/ja077633z. Epub 2008 Apr 29.
High level ab initio computations in vacuum and with the IEFPCM implicit solvent model are carried out on 5-(hydroxymethyl)tetrahydropyran to investigate the effects of water on the exocyclic torsional surface. Rotamer populations evaluated from the omega(C-C-C-O), theta(C-C-C-O) solvent surface agree almost quantitatively with experimental values for the closely related methyl 4-deoxy-alpha-D-xylohexopyranoside. Potentials of mean force obtained from the two surfaces show substantial solvent stabilization of the TG (omega = 180 +/- 60 degrees) rotamer and the barriers at omega= 120 and 240 degrees but solvent destabilization at the cis barrier (omega = 0 degrees). Natural bond orbital analyses indicate that energetics of these effects are largely explained by overstabilization of the vacuum GT (omega= 60 +/- 60 degrees) and GG (omega = 300 +/- 60 degrees) rotamers. Solvent stabilization of theta conformations provides entropic stabilization.
在真空条件下以及使用IEFPCM隐式溶剂模型对5-(羟甲基)四氢吡喃进行了高水平的从头算计算，以研究水对外环扭转表面的影响。从ω(C-C-C-O)、θ(C-C-C-O)溶剂表面评估得到的旋转异构体群体与密切相关的4-脱氧-α-D-吡喃木糖甲基苷的实验值几乎在数量上一致。从这两个表面获得的平均力势表明，TG（ω = 180 ± 60度）旋转异构体有显著的溶剂稳定作用，在ω = 120度和240度处有势垒，但在顺式势垒（ω = 0度）处有溶剂去稳定作用。自然键轨道分析表明，这些效应的能量学很大程度上可以通过真空GT（ω = 60 ± 60度）和GG（ω = 300 ± 60度）旋转异构体的过度稳定来解释。θ构象的溶剂稳定作用提供了熵稳定作用。
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