Grossert J Stuart, Boschi Donatella, Lolli Marco L, White Robert L
Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada.
Dipartimento di Scienza e Tecnologia del Farmaco (DSTF), Università degli Studi di Torino, Torino, Italy.
Eur J Mass Spectrom (Chichester). 2024 Feb;30(1):38-46. doi: 10.1177/14690667231214672. Epub 2023 Nov 17.
Gas phase fragmentation reactions of monoprotonated 4-(3-aminopropyl)- and 4-(4-aminobutyl)-3-hydroxyfurazan were investigated to examine potential interactions between functional groups. The two heterocyclic alkyl amines were ionized by electrospray ionization (ESI, positive mode) and fragmented using tandem mass spectrometry (MS/MS). The fragmentation pathways were characterized using pseudo MS experiments, precursor-ion scans, and density functional computations. For both heterocyclic ions, loss of ammonia was the only fragmentation process observed at low collision energies. Computational analysis indicated that the most feasible mechanism was intramolecular nucleophilic displacement of ammonia from the protonated ω-aminoalkyl side chain by N5 of the furazan ring. The alkylated nitrogen in the resulting bicyclic product ion facilitated N-O bond cleavage; subsequent neutral losses of nitric oxide (NO) and carbon monoxide (CO) occurred by homolytic bond cleavages. Next in the multistep sequence, neutral loss of ethylene from a radical cation was observed. A less favorable, competing fragmentation pathway of protonated 4-(3-aminopropyl)-3-hydroxyfurazan was consistent with cleavage of the 3-hydroxyfurazan ring and losses of NO and CO. Overall, the similar fragmentation behavior found for protonated 4-(3-aminopropyl)- and 4-(4-aminobutyl)-3-hydroxyfurazan differed from that previously characterized for furazan analogs with shorter alkyl chains. These observations demonstrate that a small change in the structure of multifunctional, heterocyclic alkyl amines may significantly influence interactions between distinct functional groups and the nature of the fragmentation process.
研究了单质子化的4-(3-氨丙基)-3-羟基呋咱和4-(4-氨丁基)-3-羟基呋咱的气相碎裂反应,以考察官能团之间的潜在相互作用。这两种杂环烷基胺通过电喷雾电离(ESI,正模式)进行离子化,并使用串联质谱(MS/MS)进行碎裂。通过伪MS实验、前体离子扫描和密度泛函计算对碎裂途径进行了表征。对于这两种杂环离子,在低碰撞能量下观察到的唯一碎裂过程是氨的损失。计算分析表明,最可行的机制是呋咱环的N5对质子化ω-氨烷基侧链上的氨进行分子内亲核取代。所得双环产物离子中的烷基化氮促进了N-O键的断裂;随后通过均裂键断裂发生一氧化氮(NO)和一氧化碳(CO)的中性损失。在多步序列中的下一步,观察到自由基阳离子中性损失乙烯。质子化的4-(3-氨丙基)-3-羟基呋咱的一种不太有利的竞争碎裂途径与3-羟基呋咱环的断裂以及NO和CO的损失一致。总体而言,质子化的4-(3-氨丙基)-3-羟基呋咱和4-(4-氨丁基)-3-羟基呋咱的类似碎裂行为与先前表征的具有较短烷基链的呋咱类似物不同。这些观察结果表明,多功能杂环烷基胺结构的微小变化可能会显著影响不同官能团之间的相互作用以及碎裂过程的性质。