Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan.
Magn Reson Chem. 2010 Oct;48(10):811-7. doi: 10.1002/mrc.2676.
The reaction mechanism for the biomimetic synthesis of tryptophan from indole and serine in the presence of Ac(2)O in AcOH was investigated. Although the time-course (1)H-NMR spectra of the reaction of 5-methoxyindole with N-acetylserine were measured in the presence of (CD(3)CO)(2)O in CD(3)CO(2)D, the reactive intermediate could not be detected. This reaction was conducted without 5-methoxyindole in order to elucidate the reactive intermediate, but the intermediate could not be isolated from the reaction mixture. Since the intermediate would be expected to have a very short life time, and therefore be very difficult to detect by conventional analytical methods, the structure of the intermediate was elucidated using a 2D-NMR technique, diffusion-ordered spectroscopy (DOSY). Two intermediates were detected and confirmed to be 2-methyl-4-methyleneoxazol-5(4H)-one and 2-methyl-4-hydroxymethyloxazol-5(4H)-one. The present results demonstrated that DOSY is a powerful tool for the detection of unstable intermediates.
在 AcOH 中存在 Ac(2)O 时，从吲哚和丝氨酸仿生合成色氨酸的反应机制进行了研究。尽管在 (CD(3)CO)(2)O 存在下测量了 5-甲氧基吲哚与 N-乙酰丝氨酸的反应的时程 (1)H-NMR 谱，但无法检测到反应性中间体。进行了没有 5-甲氧基吲哚的该反应，以阐明反应性中间体，但中间体不能从反应混合物中分离出来。由于预期中间体具有非常短的寿命，并且因此非常难以通过常规分析方法检测到，因此使用二维 NMR 技术，扩散排序光谱学 (DOSY) 阐明了中间体的结构。检测到两种中间体，并确认它们分别是 2-甲基-4-亚甲基恶唑-5(4H)-酮和 2-甲基-4-羟甲基恶唑-5(4H)-酮。本研究结果表明，DOSY 是检测不稳定中间体的有力工具。
