Abstract Thermochemical ester bond cleavage in the phospholipid phosphatidylcholine (PC) was evaluated at reaction temperatures between ca. 20-60 °C using a series of lithium and zinc halides: lithium chloride, lithium bromide, lithium iodide, zinc chloride, zinc bromide, and zinc iodide. Hydroxides, produced via reaction between lithium or zinc halides and potassium hydroxide (KOH), attacked and cleaved selective phosphate and carbonyl ester bonds found in PC. Cleavage reaction efficacy was studied over a wide range of reaction conditions, 2 and 4 hours at 21, 30, 50 and 60 °C, using attenuated total reflectance and transmission FTIR (ATR-FTIR) spectroscopy. FTIR spectral analysis of neat (unreacted) and reacted PC showed qualitative and quantitative evidence of carbonyl and phosphonyl ester bond cleavage as indicated by the appearance and increase in the asymmetric carboxylate anion stretch (∼1577 cm-1) and symmetric phosphonyl dianion stretch (∼1010 cm-1) peaks, respectively. Ester cleavage in PC was demonstrated under extremely mild conditions using lithium hydroxide. In addition, the hydrolysis was found to be selective, leaving the zwitterionic phosphorylcholine group intact. Reaction time and temperature had little to no effect in promoting hydroxide attack on the ester bonds found in PC. Finally, the results of this study show that a non-enzymatic cleavage reaction methodology based on lithium hydroxide can be used for selective ester hydrolysis under extremely mild conditions. This ester hydrolysis method allows for a fast, low temperature, and selective cleavage using a chemical catalyst.

中文翻译：

---

磷脂酰胆碱中选择性酯键的氢氧化物催化裂解：FTIR 研究

摘要 在约 10 ℃ 之间的反应温度下评估了磷脂磷脂酰胆碱 (PC) 中的热化学酯​​键断裂。20-60°C使用一系列的锂和锌卤化物：氯化锂、溴化锂、碘化锂、氯化锌、溴化锌和碘化锌。通过卤化锂或卤化锌与氢氧化钾 (KOH) 之间的反应产生的氢氧化物会攻击并裂解 PC 中的选择性磷酸酯和羰基酯键。使用衰减全反射和透射 FTIR (ATR-FTIR) 光谱，在 21、30、50 和 60 °C 下，2 小时和 4 小时，在广泛的反应条件下研究了裂解反应的功效。纯（未反应）和反应后的 PC 的 FTIR 光谱分析显示了羰基和膦酰基酯键断裂的定性和定量证据，如不对称羧酸根阴离子拉伸（~1577 cm-1）和对称膦酰基双阴离子拉伸（~ 1010 cm-1) 峰。使用氢氧化锂在极其温和的条件下证明了 PC 中的酯裂解。此外，发现水解具有选择性，两性离子磷酸胆碱基团保持完整。反应时间和温度对促进氢氧化物对 PC 中酯键的侵蚀几乎没有影响。最后，这项研究的结果表明，基于氢氧化锂的非酶促裂解反应方法可用于在极其温和的条件下进行选择性酯水解。