MODELING OF ALDOPYRANOSYL RING PUCKERING WITH MM3(92)
MODELING OF ALDOPYRANOSYL RING PUCKERING WITH MM3(92)
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DOI：
10.1016/0008-6215(94)00185-5
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发表时间：
1994-11-01
影响因子：
3.1
通讯作者：
REILLY, PJ
中科院分区：
文献类型：
--
作者：
DOWD, MK;FRENCH, AD;REILLY, PJ
分子力学算法MM 3被用来计算具有全范围形状的吡喃醛糖环的能量表面。能量被标绘在克雷默和波普尔的Phi-Theta折叠坐标上。模型吡喃糖基环的C-4（1）构象对于D-阿洛糖、D-半乳糖、D-葡萄糖、D-甘露糖和D-塔罗糖的两种端基异构体是主要的，β-D-吡喃阿卓糖、β-D-吡喃古洛糖和β-D-吡喃艾杜糖的C-4（1）构象也是主要的。预测α-D-吡喃阿卓糖作为C-1（4）和C-4（1）的平衡存在，α-D-吡喃艾杜糖作为S-0（2）、C-1（4）和C-4（1）之间的平衡存在，并且α-D-吡喃古洛糖主要是C-4（1），但具有来自C-1（4）（18%）和S-0（2）（9%）的一些贡献。计算的和测量的氢-氢耦合常数一致，虽然在水中的β端基异构体的能量系统地低，平均为0.4千卡/摩尔。因为预测的异头比的误差很小，并且对于八种己糖是相似的，并且因为对溶剂的唯一让步是介电常数为3.0，所以特定溶剂的影响显然很小。
The molecular mechanics algorithm MM3 was used to compute energy surfaces for aldopyranosyl rings having a full range of shapes. Energies were plotted against the Phi-Theta puckering coordinates of Cremer and Pople. The C-4(1) conformations of the model pyranosyl rings are dominant for both anomers of D-allose, D-galactose, D-glucose, D-mannose, and D-talose, as are the C-4(1) conformations of beta-D-altropyranose, beta-D-gulopyranose, and beta-D-idopyranose. alpha-D-Altropyranose is predicted to exist as an equilibrium of C-1(4) and C-4(1), alpha-D-idopyranose as an equilibrium among S-0(2), C-1(4), and C-4(1), and alpha-D-gulopyranose is predominately C-4(1) but has some contribution from C-1(4) (18%) and S-0(2) (9%). The calculated and measured hydrogen-hydrogen coupling constants agree well, although the energies for the beta anomers in water are systematically low by an average of 0.4 kcal/mol. Because the errors in the predicted anomeric ratios are small and are similar for the eight hexoses, and because the only concession to the solvent was a dielectric constant of 3.0, specific solvent effects are apparently small.