Conformational analysis of the disaccharide methyl α- D -mannopyranosyl-(1→3)-2- O -acetyl-β- D -mannopyranoside monohydrate
Conformational analysis of the disaccharide methyl α- D -mannopyranosyl-(1→3)-2- O -acetyl-β- D -mannopyranoside monohydrate
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二糖甲基α-D-吡喃甘露糖基-(1-3)-2-O-乙酰基-β-D-吡喃甘露糖苷一水合物的构象分析
DOI：
10.1107/s2053229619004728
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
Serianni, Anthony S.
中科院分区：
文献类型：
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作者：
Zhang, Wenhui;Wu, Qingquan;Oliver, Allen G.;Serianni, Anthony S.
本文测定了α-d-甘露糖基-（1→3）-2-O-乙酰基-β-d-甘露糖苷一水合物（Ⅱ）的晶体结构，并与α-d-甘露糖基的结构参数进行了比较。单-O-乙酰化似乎促进了（II）的结晶，这是从尽管反复尝试仍难以结晶甲基α-d-吡喃甘露糖基-（1→3）-β-d-吡喃甘露糖苷推断的。在（II）中的O-乙酰基侧链的构象性质是类似于那些在最近的研究中观察到的全乙酰化的含甘露糖的寡糖，具有优选的几何形状，其中C2-H2键遮蔽的C=O键的乙酰基。O-乙酰化后，（II）中的C2-O2键延长了约0.02π。描述（II）内部O-糖苷键构象的phi（φ）和psi（ψ）扭转角与最近在水溶液中用NMR光谱法用统计程序MA′AT测定的未乙酰化（II）的扭转角相似，但ψ（Δ = ψ 16°）的差异大于φ（Δ = ψ 6°）。
The crystal structure of methyl α-d-mannopyranosyl-(1→3)-2-O-acetyl-β-d-mannopyranoside monohydrate, C15H26O12·H2O, (II), has been determined and the structural parameters for its constituent α-d-mannopyranosyl residue compared with those for methyl α-d-mannopyranoside. Mono-O-acetylation appears to promote the crystallization of (II), inferred from the difficulty in crystallizing methyl α-d-mannopyranosyl-(1→3)-β-d-mannopyranoside despite repeated attempts. The conformational properties of the O-acetyl side chain in (II) are similar to those observed in recent studies of peracetylated mannose-containing oligosaccharides, having a preferred geometry in which the C2—H2 bond eclipses the C=O bond of the acetyl group. The C2—O2 bond in (II) elongates by ∼0.02 Å upon O-acetylation. The phi (φ) and psi (ψ) torsion angles that dictate the conformation of the internal O-glycosidic linkage in (II) are similar to those determined recently in aqueous solution by NMR spectroscopy for unacetylated (II) using the statistical program MA′AT, with a greater disparity found for ψ (Δ = ∼16°) than for φ (Δ = ∼6°).