The effect of electrostatic interactions on conformational equilibria of multiply substituted tetrahydropyran oxocarbenium ions.
The effect of electrostatic interactions on conformational equilibria of multiply substituted tetrahydropyran oxocarbenium ions.
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DOI：
10.1021/jo8017846
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发表时间：
2009-01-16
期刊：
影响因子：
--
通讯作者：
Woerpel KA
中科院分区：
文献类型：
--
作者：
Yang MT;Woerpel KA
通过分析光谱、计算和反应性数据，确定了与糖基阳离子相关的二氧碳鎓离子的三维结构。二氧碳鎓离子的假设低能结构与实验确定的 1H NMR 耦合常数和亲核取代反应的非对映选择性结果相关。该方法证实了C-3烷氧基取代体系的假轴偏好，并揭示了C-5烷氧基甲基的构象偏好。尽管单取代的 C-5 烷氧基甲基取代基优选伪赤道取向，但 C-5-C-6 键旋转受静电效应控制。反式4,5-二取代四氢吡喃基系统的优选双轴构象异构体强调了静电效应在决定构象平衡中的重要性。在2-脱氧甘露糖体系中，尽管空间效应影响C-5烷氧基甲基取代基的取向，但由于静电稳定性，全轴构象异构体受到青睐。
The three-dimensional structures of dioxocarbenium ions related to glycosyl cations were determined by an analysis of spectroscopic, computational, and reactivity data. Hypothetical low-energy structures of the dioxocarbenium ions were correlated with both experimentally determined 1H NMR coupling constants and diastereoselectivity results from nucleophilic substitution reactions. This method confirmed the pseudoaxial preference of C-3 alkoxy-substituted systems and revealed the conformational preference of the C-5 alkoxymethyl group. Although the monosubstituted C-5 alkoxymethyl substituent preferred a pseudoequatorial orientation, the C-5–C-6 bond rotation was controlled by an electrostatic effect. The preferred diaxial conformer of the trans-4,5-disubstituted tetrahydropyranyl system underscored the importance of electrostatic effects in dictating conformational equilibria. In the 2-deoxymannose system, although steric effects influenced the orientation of the C-5 alkoxymethyl substituent, the all-axial conformer was favored because of electrostatic stabilization.
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DOI：
10.1021/ci0000272
发表时间：
2000-09-01
期刊：
JOURNAL OF CHEMICAL INFORMATION AND COMPUTER SCIENCES
影响因子：
--
作者：
Amat, L;Carbó-Dorca, R
通讯作者：
Carbó-Dorca, R
影响因子：
2.9
作者：
Anizelli, Pedro R.;Vilcachagua, Janaina D.;Tormena, Claudio F.
通讯作者：
Tormena, Claudio F.
影响因子：
3.9
作者：
Davies, GJ;Ducros, VMA;Zechel, DL
通讯作者：
Zechel, DL
影响因子：
15
作者：
Heck, MP;Vincent, SP;Mioskowski, C
通讯作者：
Mioskowski, C
影响因子：
3.6
作者：
Dudley, TJ;Smoliakova, IP;Hoffmann, MR
通讯作者：
Hoffmann, MR