Conformational equilibria of ephedrine and pseudoephedrine and hydrogen bonding
Conformational equilibria of ephedrine and pseudoephedrine and hydrogen bonding
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麻黄碱和伪麻黄碱的构象平衡及氢键
DOI：
10.1002/mrc.1260300905
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发表时间：
1992
影响因子：
2
通讯作者：
John D. Roberts
中科院分区：
文献类型：
--
作者：
H. Tsai;John D. Roberts
质子核磁共振谱表明，麻黄碱作为氧化氘中的游离碱，倾向于采用反式邻氢构象，尽管在非极性溶剂（如氘代三氯甲烷）中，如先前报道的那样，偏向邻氢构象是有利的。共轭酸主要含有稀氢。相比之下，氧化氘中的非质子化和质子化形式的伪麻黄碱的反式氢旋转异构体均占主导地位。在确定这些物质的构象偏好时，氢键不太可能像通常假设的那么重要。
Proton NMR spectra suggest that the conformation with trans vicinal hydrogens is favored for ephedrine as the free base in deuterium oxide, although in non‐polar solvents, such as deuteriotrichloromethane, the gauche vicinal hydrogen conformations are favored, as has been reported previously. The conjugate acid has primarily gauche hydrogens. In contrast, the trans‐hydrogen rotamers of pseudoephedrine dominate for both the non‐protonated and protonated forms in deuterium oxide. Hydrogen bonding is unlikely to be as important as usually assumed in determining the conformational preferences of these substances.