Glycosidic linkage, N -acetyl side-chain, and other structural properties of methyl 2-acetamido-2-deoxy-β- D -glucopyranosyl-(1→4)-β- D -mannopyranoside monohydrate and related compounds
Glycosidic linkage, N -acetyl side-chain, and other structural properties of methyl 2-acetamido-2-deoxy-β- D -glucopyranosyl-(1→4)-β- D -mannopyranoside monohydrate and related compounds
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甲基2-乙酰氨基-2-脱氧-β-D-吡喃葡萄糖基-(1-4)-β-D-吡喃甘露糖苷一水合物及相关化合物的糖苷键、N-乙酰基侧链和其他结构特性
DOI：
10.1107/s2053229620001515
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Serianni, Anthony S.
中科院分区：
文献类型：
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作者：
Zhang, Wenhui;Meredith, Reagan J.;Oliver, Allen G.;Carmichael, Ian;Serianni, Anthony S.
测定了2-乙酰氨基-2-脱氧-β-d-吡喃葡萄糖基-（1→4）-β-d-吡喃甘露糖苷一水合物（C15 H27 NO11·H2O）的晶体结构，并将其结构性质与β-GlcNAc-吡喃己醛糖基环上带有N-乙酰基侧链的单糖和二糖进行了比较。这些侧链中的价键角和扭转角相对均匀，但C-N（酰胺）和C-O（羰基）键长取决于与羰基O原子和N-H氢的氢键状态。相对于没有氢键的N-乙酰基侧链，其中羰基O原子作为氢键受体的那些侧链显示延长的C-O键和缩短的C-N键。通过密度泛函理论（DFT）计算再现了这种行为，表明酰胺共振形式对实验C-N和C-O键长的相对贡献取决于溶剂化状态，从而预期酰胺顺反异构化的活化势垒将取决于环境的极性。DFT计算还揭示了残基间氢键和β-（1→4）O-糖苷键中或附近的一些键角对键扭转角θ和θ的依赖性的有用预测信息。超曲面与键C-O-C键角和总能量相关的α和β是足够相似的，使前者成为后者的代理。
The crystal structure of methyl 2-acetamido-2-deoxy-β-d-glycopyranosyl-(1→4)-β-d-mannopyranoside monohydrate, C15H27NO11·H2O, was determined and its structural properties compared to those in a set of mono- and disaccharides bearing N-acetyl side-chains in βGlcNAc aldohexopyranosyl rings. Valence bond angles and torsion angles in these side chains are relatively uniform, but C—N (amide) and C—O (carbonyl) bond lengths depend on the state of hydrogen bonding to the carbonyl O atom and N—H hydrogen. Relative to N-acetyl side chains devoid of hydrogen bonding, those in which the carbonyl O atom serves as a hydrogen-bond acceptor display elongated C—O and shortened C—N bonds. This behavior is reproduced by density functional theory (DFT) calculations, indicating that the relative contributions of amide resonance forms to experimental C—N and C—O bond lengths depend on the solvation state, leading to expectations that activation barriers to amide cis–trans isomerization will depend on the polarity of the environment. DFT calculations also revealed useful predictive information on the dependencies of inter-residue hydrogen bonding and some bond angles in or proximal to β-(1→4) O-glycosidic linkages on linkage torsion angles ϕ and ψ. Hypersurfaces correlating ϕ and ψ with the linkage C—O—C bond angle and total energy are sufficiently similar to render the former a proxy of the latter.