J Org Chem. 2018 Nov 2;83(21):13363-13369. doi: 10.1021/acs.joc.8b02151. Epub 2018 Oct 22.
The hydrolytic decomposition of four peptides containing S-aroylthiooximes (SATOs) with variable N-arylidene substituents was investigated in 10 aqueous buffer solutions at pH values ranging from 6.0 to 10.9. UV-vis spectroscopy was employed to study the reaction kinetics, which revealed V-shaped pH-rate profiles for all peptides with a minimum near pH 8, suggesting a change from an acid-catalyzed to a base-activated reaction. Hammett plots showed positive ρ values above pH 8 and negative ρ values below pH 8, providing further evidence for a mechanism change. Based on these data, along with mass spectral evidence, we propose specific acid catalysis under mildly acidic and neutral conditions and multiple base-promoted decomposition reactions under mildly basic conditions.
在 pH 值范围从 6.0 到 10.9 的 10 种水性缓冲溶液中，研究了四种含有 S-芳酰硫肟（SATOs）的肽的水解分解，其中 N-芳基亚乙烯基取代基不同。采用紫外可见光谱法研究反应动力学，结果表明所有肽的 V 形 pH-速率曲线，在 pH 8 附近达到最小值，表明反应从酸催化转变为碱激活。Hammett 图显示 pH 8 以上为正 ρ 值，pH 8 以下为负 ρ 值，进一步证明了机制的变化。基于这些数据以及质谱证据，我们提出了在弱酸性和中性条件下的特定酸催化以及在弱碱性条件下的多种碱促进分解反应。
