Characterization of N,N′-substituted ureas was found to be challenging by nuclear magnetic resonance (NMR) spectroscopy, particularly N-di- and tri-alkylated ureas because of the absence of adjacent protons. In the present study, electrospray ionization tandem mass spectrometry has been used to differentiate positional isomeric pairs and to characterize a series of N,N′-substituted ureas, as these compounds have significant importance for drug discovery. Additionally, urea is an essential functionality in several bioactive compounds as well as a variety of clinically approved therapies.

中文翻译：

---

使用电喷雾电离串联质谱法合成和表征一系列 N,N'-取代的尿素衍生物：位置异构体的区分

通过核磁共振 (NMR) 光谱发现N,N'-取代脲的表征具有挑战性，尤其是N-二-和三-烷基化脲，因为没有相邻的质子。在本研究中，电喷雾电离串联质谱已用于区分位置异构对并表征一系列N,N'-取代的脲，因为这些化合物对药物发现具有重要意义。此外，尿素是几种生物活性化合物以及各种临床批准的疗法中必不可少的功能。