The biologically active alkaloid muscimol is present in fly agaric mushroom (Amanita muscaria), and its structure and action is related to human neurotransmitter γ‐aminobutyric acid (GABA). The current study reports on determination of muscimol form present in water solution using multinuclear 1H and 13C nuclear magnetic resonance (NMR) experiments supported by density functional theory molecular modeling. The structures of three forms of free muscimol molecule both in the gas phase and in the presence of water solvent, modeled by polarized continuous model, and nuclear magnetic isotropic shieldings, the corresponding chemical shifts, and indirect spin–spin coupling constants were calculated. Several J‐couplings observed in proton and carbon NMR spectra, not available before, are reported. The obtained experimental spectra, supported by theoretical calculations, favor the zwitterion form of muscimol in water. This structure differs from NH isomer, previously determined in dimethyl sulfoxide (DMSO) solution. In addition, positions of signals C3 and C5 are reversed in both solvents.

中文翻译：

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苍蝇木耳 (Amanita muscaria) 在水中的 muscimol 是什么形式？分子模型支持的 NMR 实验洞察

具有生物活性的生物碱麝香酚存在于木耳（Amanita muscaria）中，其结构和作用与人体神经递质γ-氨基丁酸（GABA）有关。目前的研究报告了使用由密度泛函理论分子模型支持的多核 1H 和 13C 核磁共振 (NMR) 实验测定水溶液中存在的蕈蕈醇形式。通过极化连续模型和核磁各向同性屏蔽建模，在气相和水溶剂存在下三种形式的游离 muscimol 分子的结构、相应的化学位移和间接自旋-自旋耦合常数被计算。报告了在质子和碳 NMR 光谱中观察到的几种 J 耦合，以前无法获得。得到的实验光谱，在理论计算的支持下，有利于 muscimol 在水中的两性离子形式。这种结构不同于之前在二甲基亚砜 (DMSO) 溶液中测定的 NH 异构体。此外，信号 C3 和 C5 的位置在两种溶剂中都颠倒了。