MOE Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology, Department of Chemistry, Tsinghua University, Beijing 100084, China.
State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing 100084, China.
Anal Chem. 2020 Oct 6;92(19):13470-13477. doi: 10.1021/acs.analchem.0c02896. Epub 2020 Sep 8.
The Paternò-Büchi (PB) reaction is a photochemical reaction involving [2 + 2] cycloaddition between electronically excited carbonyl and carbon-carbon double bond (C═C). It has been established as a lipid derivatization strategy, leading to confident assignment of C═C locations in lipids when coupled with tandem mass spectrometry (MS/MS). Although acetone and several aryl-containing ketones or aldehydes have been explored as PB reagents, the chemical properties critical to achieving efficient conversion and minimum side reactions remain unclear. Herein, we investigated a set of acetophenone (AP) derivatives, aiming to provide insights into the development of new PB reagents with enhanced performance for lipid analysis. For AP derivatives, we found that electron-withdrawing groups (e.g., -F and -CF) on the benzene ring improved the overall conversion, while a bulky group at the position decreased the conversion. Norrish Type I cleavage was largely diminished; however, the Norrish Type II side reaction was more competitive, producing products isomeric to the PB reaction products. Among all AP derivatives tested, 2',4',6'-trifluoroacetophenone (triFAP) showed the best performance. It offered a relatively high PB yield (20-30%) for different types of C═C, high sensitivity (sub-nM) for C═C identification, and accurate isomer quantitation. Due to the significantly reduced chemical interferences in shotgun analysis, triFAP provided better performance than that from acetone PB-MS/MS. An offline triFAP PB reaction was implemented in a liquid chromatography analysis workflow, which enabled the large-scale identification of phospholipids including C═C location isomers from a complex lipid extract.
帕特纳-布希（PB）反应是一种涉及电子激发羰基和碳-碳双键（C═C）之间[2 + 2]环加成的光化学反应。当与串联质谱（MS/MS）结合使用时，它已被确立为一种脂质衍生化策略，可在脂类中对 C═C 位置进行可靠的分配。尽管已经探索了丙酮和几种含芳基的酮或醛作为 PB 试剂，但对于实现有效转化和最小副反应的关键化学性质仍不清楚。在此，我们研究了一组苯乙酮（AP）衍生物，旨在为开发具有增强脂质分析性能的新型 PB 试剂提供思路。对于 AP 衍生物，我们发现苯环上的吸电子基团（例如 -F 和 -CF）提高了整体转化率，而位置上的大基团则降低了转化率。Norrish Type I 裂解大大减少；然而，Norrish Type II 副反应更具竞争力，生成与 PB 反应产物异构的产物。在所测试的所有 AP 衍生物中，2'，4'，6'-三氟苯乙酮（triFAP）表现出最佳性能。它为不同类型的 C═C 提供了相对较高的 PB 产率（20-30%）、高灵敏度（亚纳摩尔）用于 C═C 的鉴定以及准确的异构体定量。由于在 shotgun 分析中化学干扰大大减少，triFAP 提供的性能优于丙酮 PB-MS/MS。离线 triFAP PB 反应在液相色谱分析工作流程中实现，这使得能够从复杂的脂质提取物中大规模鉴定包括 C═C 位置异构体在内的磷脂。
