Abstract 2,4-substituted thieno[3,2-d]pyrimidines, with different l -amino acid methyl ester substituent on 4-C and methyl or methylthio substituent on 2-C, showed a complex and analytically valuable fragmentation behaviour under positive ion electrospray ionization collision-induced dissociation ((+)-ESI-CID) mass spectrometry. Protonated 2,4-substituted thieno[3,2-d]pyrimidines firstly lose a neutral fragment C2H4O2 (MS2) and the ion [M + H - 60]+ thus formed, then dissociates by losing of extended series of neutral molecule fragmentation from amino acid methyl ester substituent, in competition with the expulsion of CS or CH3SH and other direct bond scissions. Moreover, losing of NH3, CHN and CH2NH from the precursor ions of [M + H - 60]+ were proposed to occur via rearrangements. The formation of diagnostic product ions and the series neutral eliminations provided information about the properties of substituents, assisting their characterization via MS/MS, high-resolution mass spectrometry, the hydrogen/deuterium exchange experiment and density functional theory (DFT) calculations. The proposed fragmentation patterns of these compounds give an insight into the understanding of gas-phase reactions in mass spectrometric studies of thieno[3,2-d]pyrimidine derivatives.

中文翻译：

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噻吩并[3,2-dd]嘧啶衍生物的电喷雾电离碰撞诱导解离

摘要 2,4-取代的噻吩并[3,2-d]嘧啶，在 4-C 上具有不同的 l-氨基酸甲酯取代基，在 2-C 上具有甲基或甲硫基取代基，在正离子下表现出复杂且具有分析价值的碎裂行为。电喷雾电离碰撞诱导解离 ((+)-ESI-CID) 质谱。质子化的 2,4-取代的噻吩并 [3,2-d] 嘧啶首先失去一个中性片段 C2H4O2 (MS2) 和由此形成的离子 [M + H - 60]+，然后通过失去扩展系列的中性分子碎片而解离氨基酸甲酯取代基，与 CS 或 CH3SH 的排斥以及其他直接断键竞争。此外，[M + H - 60]+ 的母离子失去 NH3、CHN 和 CH2NH 被认为是通过重排发生的。诊断性子离子的形成和系列中性消除提供了有关取代基性质的信息，有助于通过 MS/MS、高分辨率质谱、氢/氘交换实验和密度泛函理论 (DFT) 计算对其进行表征。这些化合物的拟议碎裂模式有助于深入了解噻吩并 [3,2-d] 嘧啶衍生物的质谱研究中的气相反应。