1
|
Mane SS, Ghaste M, Dearden DV. Mass spectrometry-based gas phase intramolecular benzyl migration in sparsentan, a novel endothelin and angiotensin II receptor antagonist. JOURNAL OF MASS SPECTROMETRY : JMS 2023; 58:e4980. [PMID: 37903508 DOI: 10.1002/jms.4980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 09/19/2023] [Accepted: 10/05/2023] [Indexed: 11/01/2023]
Abstract
We report a collision-induced dissociation (CID) based gas phase rearrangement study using quadrupole time-of-flight mass spectrometry coupled with liquid chromatography on a novel endothelin and angiotensin II receptor antagonist, sparsentan. We performed tandem mass spectrometry to identify precursor and fragment ion relationships and assigned structures for major fragment ions. We propose a benzyl migration mechanism based on bond length measurements in density functional theory (B3LYP/6-31+G*) optimized geometries of protonated sparsentan and its m/z 547 fragment. Protonated sparsentan undergoes loss of ethanol, which yields a resonance-stabilized benzylic cation with m/z 547, which further fragments into m/z 353 via benzyl migration, where the benzylic cation migrates to one of the nucleophilic nitrogen atoms followed by proton transfer from the sulfonamide nitrogen to a carbonyl oxygen, resulting in a neutral loss of mass 194. Further fragmentation of m/z 353 results in m/z 258, which undergoes radical and neutral loss to yield m/z 193 and 194, respectively. The proposed mechanism of generation of m/z 353 was confirmed by CID of deuterated sparsentan. Considering the importance of gas phase rearrangements of organic molecules in structural identifications as well as the novelty of the molecule, these findings will be helpful for future studies to predict gas phase benzyl migration in sparsentan analogs and for degradation product and metabolite identification of sparsentan and its analogs using LC-MS.
Collapse
Affiliation(s)
- Sudam S Mane
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah, 84602-1030, USA
| | - Manoj Ghaste
- Analytical Chemistry Department, Nelson Laboratories, 6280 S. Redwood Road, Salt Lake City, Utah, 84123, USA
| | - David V Dearden
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah, 84602-1030, USA
| |
Collapse
|
2
|
Nikolić D, Lankin DC. Low Energy Collision-Induced Dissociation of Azepine Pictet-Spengler Adducts of Nω-Methylserotonin. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:182-192. [PMID: 36648409 DOI: 10.1021/jasms.2c00247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Cimitrypazepines are a class of natural products produced by Pictet-Spengler condensation of Nω-methylserotonin and aldehydes in a manner that produces a seven-membered azepine ring. In this study, the fragmentation behavior of this class of molecules under low-energy CID was investigated in detail. Proposed mechanisms of fragmentation were supported by deuterium labeling and DFT calculations. Loss of methylamine and methylenimine were dominant fragmentation pathways of analogs containing an aliphatic side chain. Loss of methylenimine was found to proceed via unusual methyl cation transfer. Fragmentation of analogs containing an aromatic side chain was strongly influenced by the nature of the substituents and proceeded via a novel retro-Pictet-Spengler pathway and involvement of ion-neutral complexes. In some cases, a gas-phase interconversion between the azepine and β-carboline ring was observed during fragmentation. Detailed analysis of fragmentation behavior provided in this study will serve as a valuable guide for the discovery of new analogs from natural sources.
Collapse
Affiliation(s)
- Dejan Nikolić
- Department of Pharmaceutical Sciences UIC/NIH Center for Botanical Dietary Supplements Research College of Pharmacy, University of Illinois at Chicago 833 S. Wood St., Chicago, Illinois 60612-7231, United States
| | - David C Lankin
- Department of Pharmaceutical Sciences UIC/NIH Center for Botanical Dietary Supplements Research College of Pharmacy, University of Illinois at Chicago 833 S. Wood St., Chicago, Illinois 60612-7231, United States
| |
Collapse
|
3
|
Zheng M, Zhang X, Cheng Y, Sun L, Zhang X. Hydroxyl transfer versus cyclization reaction in the gas phase: Sequential loss of NH 3 and CH 2CO from protonated phenylalanine derivatives. Front Chem 2023; 10:1094329. [PMID: 36700082 PMCID: PMC9868239 DOI: 10.3389/fchem.2022.1094329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 12/23/2022] [Indexed: 01/10/2023] Open
Abstract
Collisional activation of protonated phenylalanine derivatives deamination products leads to hydroxyl skeletal rearrangement versus cyclization reaction, and to form hydroxylbenzyl cation via elimination of CH2CO. To better clarify this unusual fragmentation reaction, accurate mass measurements experiments, native isotope experiments, multiple-stage mass spectrometry experiments, different substituents experiments, and density functional theory (DFT) calculations were carried out to investigate the dissociation mechanistic pathways of protonated phenylalanine derivatives deamination products. In route 1, a three-membered ring-opening reaction and a 1,3-hydroxyl transfer (from the carbonyl carbon atom to the interposition carbon atom of carbonyl) occurs to form 3-hydroxy-1-oxo-3-phenylpropan-1-ylium, followed by dissociation to lose CH2CO to give hydroxy (phenyl)methylium. In route 2, a successive cyclization rearrangement reaction and proton transfer occur to form a 2-hydroxylphenylpropionyl cation or protonated 2-hydroxy-4H-benzopyran, followed by dissociation to lose CH2CO or CH≡COH to give 2-hydroxylbenzyl cation. In route 3, a successive hydroxyl transfer (from the carbonyl carbon atom to the ortho carbon atom on benzene) and two stepwise proton transfer (1,2-proton transfer to the ipso-carbon atom of the phenyl ring followed by 1,3-proton transfer to the ortho carbon atom of carbonyl) occurs to form a 2-hydroxylphenylpropionyl cation, which subsequently dissociates to form 2-hydroxylbenzyl cation by elimination of CH2CO. DFT calculations suggested that route 1 was more favorable than route 2 and route 3 from a thermodynamic point of view.
Collapse
|
4
|
Zhang X, Chen H, Ji Y, Jiang K, Chen H. Sulfur Transfer Versus Phenyl Ring Transfer in the Gas Phase: Sequential Loss of CH 3OH and CH 3O-P=O from Protonated Phosphorothioates. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:459-467. [PMID: 30569428 DOI: 10.1007/s13361-018-2098-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Revised: 10/22/2018] [Accepted: 10/24/2018] [Indexed: 06/09/2023]
Abstract
Collisional activation fragmentation of protonated phosphorothioates leads to skeletal rearrangement and formation of aryl sulfenylium cation (R-PhS+) via successive eliminations of CH3OH and CH3O-P=O. To better understand this unusual fragmentation reaction, isotope-labeling experiments and density functional theory (DFT) calculations were carried out to investigate two mechanistic pathways. In route 1, a direct intramolecular transfer of the R-phenyl group occurs from the oxygen atom to the sulfur atom on thiophosphoryl to form methoxyl S-(3-methyl-4-methylsulfanyl-phenyl) phosphonium thiolate (a4), which subsequently dissociates to form the m/z 169 cation. In route 2, the sulfur atom of the thiophosphoryl group undergoes two stepwise transfer (1,4-migration to the ortho-carbon atom of the phenyl ring followed by 1,2-migration to the ipso-carbon atom) to form an intermediate isomer, which undergoes the subsequent dissociation to form the m/z 169 cation. DFT calculations suggested that route 2 was more favorable than route 1 from the point view of kinetics. Graphical Abstract.
Collapse
Affiliation(s)
- Xiaoping Zhang
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang, 330013, People's Republic of China
| | - Honghan Chen
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang, 330013, People's Republic of China
| | - Yin Ji
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang, 330013, People's Republic of China
| | - Kezhi Jiang
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China.
| | - Huanwen Chen
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang, 330013, People's Republic of China.
| |
Collapse
|
5
|
Qi P, Liang Z, Wang N, Zhao J, Chen Y, Zhou Q, Gao H, Jiang J. How Does Azo Bond Cleave in the Gas Phase? Computational and Experimental Study on the Fragmentation Mechanism of Protonated Sudan I. ChemistrySelect 2019. [DOI: 10.1002/slct.201803165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Ping Qi
- GuangZhou Institute for Food Inspection Guangzhou 511400 China
| | - Zhi‐an Liang
- GuangZhou Institute for Food Inspection Guangzhou 511400 China
| | - Ning Wang
- GuangZhou Institute for Food Inspection Guangzhou 511400 China
| | - Jin‐Li Zhao
- GuangZhou Institute for Food Inspection Guangzhou 511400 China
| | - Yu‐Zhong Chen
- GuangZhou Institute for Food Inspection Guangzhou 511400 China
| | - Qing‐qiong Zhou
- GuangZhou Institute for Food Inspection Guangzhou 511400 China
| | - Hui Gao
- Key Laboratory of Molecular Target & Clinical PharmacologySchool of Pharmaceutical Sciences & the Fifth Affiliated HospitalGuangzhou Medical University Guangzhou 511436 China
| | - Ji‐Jun Jiang
- Lehn Institute of Functional MaterialsSchool of ChemistrySun Yat-sen University Guangzhou 510275 China
| |
Collapse
|
6
|
Zhou Y, Guan J, Gao W, Lv S, Ge M. Quantification and Confirmation of Fifteen Carbamate Pesticide Residues by Multiple Reaction Monitoring and Enhanced Product Ion Scan Modes via LC-MS/MS QTRAP System. Molecules 2018; 23:E2496. [PMID: 30274254 PMCID: PMC6222809 DOI: 10.3390/molecules23102496] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 09/14/2018] [Accepted: 09/27/2018] [Indexed: 11/17/2022] Open
Abstract
In this research, fifteen carbamate pesticide residues were systematically analyzed by ultra-high performance liquid chromatography⁻quadrupole-linear ion trap mass spectrometry on a QTRAP 5500 system in both multiple reaction monitoring (MRM) and enhanced product ion (EPI) scan modes. The carbamate pesticide residues were extracted from a variety of samples by QuEChERS method and separated by a popular reverse phase column (Waters BEH C18). Except for the current conformation criteria including selected ion pairs, retention time and relative intensities from MRM scan mode, the presence of carbamate pesticide residues in diverse samples, especially some doubtful cases, could also be confirmed by the matching of carbamate pesticide spectra via EPI scan mode. Moreover, the fragmentation routes of fifteen carbamates were firstly explained based on the mass spectra obtained by a QTRAP system; the characteristic fragment ion from a neutral loss of CH₃NCO (-57 Da) could be observed. The limits of detection and quantification for fifteen carbamates were 0.2⁻2.0 μg kg-1 and 0.5⁻5.0 μg kg-1, respectively. For the intra- (n = 3) and inter-day (n = 15) precisions, the recoveries of fifteen carbamates from spiked samples ranged from 88.1% to 118.4%, and the coefficients of variation (CVs) were all below 10%. The method was applied to pesticide residues detection in fruit, vegetable and green tea samples taken from local markets, in which carbamates were extensively detected but all below the standard of maximum residue limit.
Collapse
Affiliation(s)
- Ying Zhou
- Jiaxing Center for Disease Control and Prevention, Zhejiang 314050, China.
| | - Jian Guan
- Jiaxing Center for Disease Control and Prevention, Zhejiang 314050, China.
| | - Weiwei Gao
- Jiaxing Center for Disease Control and Prevention, Zhejiang 314050, China.
| | - Shencong Lv
- Jiaxing Center for Disease Control and Prevention, Zhejiang 314050, China.
| | - Miaohua Ge
- Jiaxing Center for Disease Control and Prevention, Zhejiang 314050, China.
| |
Collapse
|
7
|
Cai T, Guo ZQ, Xu XY, Wu ZJ. Recent (2000-2015) developments in the analysis of minor unknown natural products based on characteristic fragment information using LC-MS. MASS SPECTROMETRY REVIEWS 2018; 37:202-216. [PMID: 27341181 DOI: 10.1002/mas.21514] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 06/02/2016] [Indexed: 06/06/2023]
Abstract
Liquid chromatography-Mass Spectrometry (LC-MS) has been widely used in natural product analysis. Global detection and identification of nontargeted components are desirable in natural product research, for example, in quality control of Chinese herbal medicine. Nontargeted components analysis continues to expand to exciting life science application domains such as metabonomics. With this background, the present review summarizes recent developments in the analysis of minor unknown natural products using LC-MS and mainly focuses on the determination of the molecular formulae, selection of precursor ions, and characteristic fragmentation patterns of the known compounds. This review consists of three parts. Firstly, the methods used to determine unique molecular formula of unknown compounds such as accurate mass measurements, MSn spectra, or relative isotopic abundance information, are introduced. Secondly, the methods improving signal-to-noise ratio of MS/MS spectra by manual-MS/MS or workflow targeting-only signals were elucidated; pure precursor ions can be selected by changing the precursor ion isolated window. Lastly, characteristic fragmentation patterns such as Retro-Diels-Alder (RDA), McLafferty rearrangements, "internal residue loss," and so on, occurring in the molecular ions of natural products are summarized. Classical application of characteristic fragmentation patterns in identifying unknown compounds in extracts and relevant fragmentation mechanisms are presented (RDA reactions occurring readily in the molecular ions of flavanones or isoflavanones, McLafferty-type fragmentation reactions of some natural products such as epipolythiodioxopiperazines; fragmentation by "internal residue loss" possibly involving ion-neutral complex intermediates). © 2016 Wiley Periodicals, Inc. Mass Spec Rev 37:202-216, 2018.
Collapse
Affiliation(s)
- Tian Cai
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
- Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, 610041, China
- University of Chinese Academy of Sciences, Beijing, 100039, China
| | - Ze-Qin Guo
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
- College of Bioengineering, Chongqing University, Chongqing, 400044, China
| | - Xiao-Ying Xu
- Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, 610041, China
| | - Zhi-Jun Wu
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
| |
Collapse
|
8
|
Nikolić D, Macias C, Lankin DC, van Breemen RB. Collision-induced dissociation of phenethylamides: role of ion-neutral complexes. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2017; 31:1385-1395. [PMID: 28558170 PMCID: PMC5555735 DOI: 10.1002/rcm.7915] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 04/21/2017] [Accepted: 05/25/2017] [Indexed: 06/07/2023]
Abstract
RATIONALE Phenethylamides are a large group of naturally occurring molecules found both in the plant and animal kingdoms. In addition, they are used as intermediates for the synthesis of pharmaceutically important dihydro- and tetrahydroisoquinolines. To enable efficient characterization of this class of molecules, a detailed mass spectrometric fragmentation study of a broad series of analogs was carried out. METHODS The test compounds were synthesized using standard methods for amide bond formation. Low-energy high-resolution tandem mass spectra were acquired on a hybrid quadrupole/time-of-flight mass spectrometer using positive ion electrospray ionization. RESULTS A total of 26 analogs were investigated in the study. Fragmentation of phenethylamides was found to proceed via intermediate ion-neutral complexes. The complexes can break down via multiple pathways including dissociation, proton transfer, Friedel-Crafts acylation, and single electron transfer. The relative contribution of each of these pathways strongly depends on the structure of the coupling amine and acid. CONCLUSIONS A general scheme for the fragmentation of phenethylamides was developed. This study further extends the knowledge base of the ion-neutral complex by discovering Friedel-Crafts acylation as a novel reaction. The strong influence of minor structural modifications on the fragmentation patterns highlights the importance of testing many analogs in order to fully predict a fragmentation pattern of a particular class of molecules.
Collapse
Affiliation(s)
- Dejan Nikolić
- Corresponding Author: Dejan Nikolić, Department of Medicinal Chemistry and Pharmacognosy, University of Illinois at Chicago, 833 S. Wood St., Chicago, IL 60612-7231, Telephone (312) 413-5867, FAX (312) 996-7107,
| | | | | | | |
Collapse
|
9
|
Ma G, Liu G, Shen S, Chai Y, Yue L, Zhao S, Pan Y. Competitive benzyl cation transfer and proton transfer: collision-induced mass spectrometric fragmentation of protonated N,N-dibenzylaniline. JOURNAL OF MASS SPECTROMETRY : JMS 2017; 52:197-203. [PMID: 28109035 DOI: 10.1002/jms.3914] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 01/14/2017] [Accepted: 01/17/2017] [Indexed: 06/06/2023]
Abstract
Collision-induced dissociation of protonated N,N-dibenzylaniline was investigated by electrospray tandem mass spectrometry. Various fragmentation pathways were dominated by benzyl cation and proton transfer. Benzyl cation transfers from the initial site (nitrogen) to benzylic phenyl or aniline phenyl ring. The benzyl cations transfer to the two different sites, and both result in the benzene loss combined with 1,3-H shift. In addition, after the benzyl cation transfers to the benzylic phenyl ring, 1,2-H shift and 1,4-H shift proceed competitively to trigger the diphenylmethane loss and aniline loss, respectively. Deuterium labeling experiments, substituent labeling experiments and density functional theory calculations were performed to support the proposed benzyl cation and proton transfer mechanism. Overall, this study enriches the knowledge of fragmentation mechanisms of protonated N-benzyl compounds. Copyright © 2017 John Wiley & Sons, Ltd.
Collapse
Affiliation(s)
- G Ma
- Deparment of Chemistry, Zhejiang University, 38 Zheda Road, Hangzhou, 310027, Zhejiang, China
| | - G Liu
- Radiation Monitoring Technical Center, Ministry of Environmental Protection of China, 306 Wen Yi Road, Hangzhou, 310012, China
| | - S Shen
- Deparment of Chemistry, Zhejiang University, 38 Zheda Road, Hangzhou, 310027, Zhejiang, China
| | - Y Chai
- College of Pharmaceutical Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
| | - L Yue
- Deparment of Chemistry, Zhejiang University, 38 Zheda Road, Hangzhou, 310027, Zhejiang, China
| | - S Zhao
- Radiation Monitoring Technical Center, Ministry of Environmental Protection of China, 306 Wen Yi Road, Hangzhou, 310012, China
| | - Y Pan
- Deparment of Chemistry, Zhejiang University, 38 Zheda Road, Hangzhou, 310027, Zhejiang, China
| |
Collapse
|
10
|
Yue L, Li J, Xie X, Guo C, Yin X, Yin Q, Chen Y, Pan Y, Ding C. Ortho-hydroxyl effect and proton transfer via ion-neutral complex: the fragmentation study of protonated imine resveratrol analogues in mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2016; 51:518-523. [PMID: 27434810 DOI: 10.1002/jms.3778] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 03/30/2016] [Accepted: 04/20/2016] [Indexed: 06/06/2023]
Abstract
The fragmentation pathways of protonated imine resveratrol analogues in the gas-phase were investigated by electrospray ionization-tandem mass spectrometry. Benzyl cations were formed in the imine resveratrol analogues that had an ortho-hydroxyl group on the benzene ring A. The specific elimination of the quinomethane neutral, CH2 = C6 H4 = O, from the two isomeric ions [M1 + H](+) and [M3 + H](+) via the corresponding ion-neutral complexes was observed. The fragmentation pathway for the related meta-isomer, ion [M2 + H](+) and the other congeners was not observed. Accurate mass measurements and additional experiments carried out with a chlorinated analogue and the trideuterated isotopolog of M1 supported the overall interpretation of the fragmentation phenomena observed. It is very helpful for understanding the intriguing roles of ortho-hydroxyl effect and ion-neutral complexes in fragmentation reactions and enriching the knowledge of the gas-phase chemistry of the benzyl cation. Copyright © 2016 John Wiley & Sons, Ltd.
Collapse
Affiliation(s)
- Lei Yue
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | - Jing Li
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
- Institute of Biological Engineering, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, Zhejiang, China
| | - Xiaodong Xie
- Department of Chemistry, Fudan University, 220 Handan Road, Shanghai, 200433, China
| | - Cheng Guo
- Cancer Institute, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China
| | - Xinchi Yin
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | - Qi Yin
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | - Yinjuan Chen
- Department of Chemistry, Fudan University, 220 Handan Road, Shanghai, 200433, China
| | - Yuanjiang Pan
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | - Chuanfan Ding
- Department of Chemistry, Fudan University, 220 Handan Road, Shanghai, 200433, China
| |
Collapse
|
11
|
Zhang X, Bai X, Fang L, Jiang K, Li Z. Decarboxylative Coupling Reaction in ESI(-)-MS/MS of 4-Nitrobenzyl 4-Hydroxybenzoates: Triplet Ion-Neutral Complex-Mediated 4-Nitrobenzyl Transfer. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:940-943. [PMID: 26926444 DOI: 10.1007/s13361-016-1339-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 01/09/2016] [Accepted: 01/10/2016] [Indexed: 06/05/2023]
Abstract
In negative electrospray ionization mass spectrometry of 4-nitrobenzyl 4-hydroxybenzoates, a decarboxylation reaction, which was significantly promoted by the presence of a nitro group on the benzyl group, competed with radical elimination reactions. Density functional theory calculations indicated that decarboxylation of deprotonated 4-nitrobenzyl vanillate occurred via a radical route involving homolytic cleavage of the Cbenzyl-O bond to give a triplet ion-neutral complex, followed by decarboxylative coupling.
Collapse
Affiliation(s)
- Xiaoping Zhang
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China
- College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, 310014, China
| | - Xingfeng Bai
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China
| | - Liwen Fang
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China
| | - Kezhi Jiang
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China.
| | - Zuguang Li
- College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, 310014, China.
| |
Collapse
|
12
|
Chai Y, Xiong X, Yue L, Jiang Y, Pan Y, Fang X. Intramolecular Halogen Transfer via Halonium Ion Intermediates in the Gas Phase. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:161-167. [PMID: 26383734 DOI: 10.1007/s13361-015-1261-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Revised: 08/31/2015] [Accepted: 09/01/2015] [Indexed: 06/05/2023]
Abstract
The fragmentation of halogen-substituted protonated amines and quaternary ammonium ions (R(1)R(2)R(3)N(+)CH2(CH2)nX, where X = F, Cl, Br, I, n = 1, 2, 3, 4) was studied by electrospray ionization tandem mass spectrometry. A characteristic fragment ion (R(1)R(2)R(3)N(+)X) resulting from halogen transfer was observed in collision-induced dissociation. A new mechanism for the intramolecular halogen transfer was proposed that involves a reactive intermediate, [amine/halonium ion]. A potential energy surface scan using DFT calculation for CH2-N bond cleavage process of protonated 2-bromo-N,N-dimethylethanamine supports the formation of this intermediate. The bromonium ion intermediate-involved halogen transfer mechanism is supported by an examination of the ion/molecule reaction between isolated ethylenebromonium ion and triethylamine, which generates the N-bromo-N,N,N-triethylammonium cation. For other halogens, Cl and I also can be involved in similar intramolecular halogen transfer, but F cannot be involved. With the elongation of the carbon chain between the halogen (bromine as a representative example) and amine, the migration ability of halogen decreases. When the carbon chain contains two or three CH2 units (n = 1, 2), formal bromine cation transfer can take place, and the transfer is easier when n = 1. When the carbon chain contains four or five CH2 units (n = 3, 4), formal bromine cation transfer does not occur, probably because the five- and six-membered cyclic bromonium ions are very stable and do not donate the bromine to the amine.
Collapse
Affiliation(s)
- Yunfeng Chai
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China
| | | | - Lei Yue
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | - You Jiang
- National Institute of Metrology, Beijing, 100013, China
| | - Yuanjiang Pan
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, China.
| | - Xiang Fang
- National Institute of Metrology, Beijing, 100013, China.
| |
Collapse
|
13
|
Shen S, Chai Y, Liu Y, Li C, Pan Y. Benzyl anion transfer in the fragmentation of N-(phenylsulfonyl)-benzeneacetamides: a gas-phase intramolecular S(N)Ar reaction. Org Biomol Chem 2015; 13:10205-11. [PMID: 26309220 DOI: 10.1039/c5ob01582k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In this study, we report a gas-phase benzyl anion transfer via intramolecular aromatic nucleophilic substitution (SNAr) during the course of tandem mass spectrometry of deprotonated N-(phenylsulfonyl)-benzeneacetamide. Upon collisional activation, the formation of the initial ion/neutral complex ([C6H5CH2(-)/C6H5SO2NCO]), which was generated by heterolytic cleavage of the CH2-CO bond, is proposed as the key step. Subsequently, the anionic counterpart, benzyl anion, is transferred to conduct the intra-complex SNAr reaction. After losing neutral HNCO, the intermediate gives rise to product ion B at m/z 231, whose structure is confirmed by comparing the multistage spectra with those of deprotonated 2-benzylbenzenesulfinic acid and (benzylsulfonyl)benzene. In addition, intra-complex proton transfer is also observed within the complex [C6H5CH2(-)/C6H5SO2NCO] to generate product ion C at m/z 182. The INC-mediated mechanism was corroborated by theoretical calculations, isotope experiments, breakdown curve, substituent experiments, etc. This work may provide further understanding of the physicochemical properties of the gaseous benzyl anion.
Collapse
Affiliation(s)
- Shanshan Shen
- Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
| | | | | | | | | |
Collapse
|
14
|
Paulose J, Achuthan RP, Linsha MPL, Mathai G, Prasanth B, Kumar Talluri MVN, Srinivas R. Protonated N-benzyl- and N-(1-phenylethyl)tyrosine amides dissociate via ion/neutral complexes. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:1577-1584. [PMID: 28339153 DOI: 10.1002/rcm.7256] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 06/08/2015] [Accepted: 06/15/2015] [Indexed: 06/06/2023]
Abstract
RATIONALE The collisional-induced dissociations (CID) of the [M+H]+ ions of molecules having benzyl groups attached to N-atoms have been proposed to involve migration of the benzyl group through the intermediacy of ion/neutral complexes (INCs). We report the investigation of the mechanism of dissociation of protonated N-benzyl- and N-(1-phenylethyl)tyrosine amides by electrospray ionization (ESI) tandem mass spectrometry (MS/MS) and density functional theory (DFT) calculations. METHODS The amides were synthesized from the corresponding amino acids and amines. The ESI-MS/MS spectra were recorded using an Agilent QTOF 6540 mass spectrometer. The DFT calculations were performed by using Gaussian 09 software. The structures of the [M+H]+ ions, intermediates, products and transition states (TS) were optimized at the B3LYP/6-31G(d,p) level of theory. RESULTS CID of the [M+H]+ ions of N-benzyltyrosine amide yields two product ions due to rearrangements: (i) the [M+H-74]+ ion (m/z 197) due to benzyl migration to the hydroxyphenyl ring and (ii) the [M+H-45]+ ion (m/z 226) due to benzyl migration to the NH2 group. DFT calculations suggest that the rearrangements occur through an INC in which the benzyl cation is the cation partner. The [M+H]+ ion of N-(1-phenylethyl)tyrosine amide rearranges to an INC of the 1-phenylethyl cation. Subsequent elimination of styrene occurs by transfer of a proton from the 1-phenylethyl cation to the neutral partner. CONCLUSIONS The [M+H]+ ions of both N-benzyl (1) and N-(1-phenylethyl) (2) tyrosine amide rearrange into INCs. The dissociation of [M+H]+ ion of 1 yields the benzyl cation and [M+H-74]+ and [M+H-45]+ due to benzyl migration to the hydroxyphenyl ring and NH2 group, respectively. However, the formation of the [M+H-74]+ ion is not observed when the aromatic ring is deactivated. The [M+H]+ ion of 2 either dissociates to form the 1-phenylethyl cation or [M+H-styrene]+ . Copyright © 2015 John Wiley & Sons, Ltd.
Collapse
Affiliation(s)
- Justin Paulose
- Department of Chemistry, Sacred Heart College, Thevara, Kochi, India
- Bharathiyar University, Coimbatore, Tamilnadu, India
| | - Revi P Achuthan
- Department of Chemistry, Sacred Heart College, Thevara, Kochi, India
- Bharathiyar University, Coimbatore, Tamilnadu, India
| | - Maria P L Linsha
- Department of Chemistry, Sacred Heart College, Thevara, Kochi, India
- Bharathiyar University, Coimbatore, Tamilnadu, India
| | - George Mathai
- Department of Chemistry, Sacred Heart College, Thevara, Kochi, India
- Bharathiyar University, Coimbatore, Tamilnadu, India
| | - B Prasanth
- National Institute of Pharmaceutical Education and Research, Hyderabad, India
| | - M V N Kumar Talluri
- National Institute of Pharmaceutical Education and Research, Hyderabad, India
| | | |
Collapse
|
15
|
Yao L, Chai Y, Sun C, Pan Y. Competitive proton and hydride transfer reactions via ion-neutral complexes: fragmentation of deprotonated benzyl N-phenylcarbamates in mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2015; 50:364-370. [PMID: 25800018 DOI: 10.1002/jms.3537] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 10/28/2014] [Accepted: 10/31/2014] [Indexed: 06/04/2023]
Abstract
The gas-phase chemistry of deprotonated benzyl N-phenylcarbamates was investigated by electrospray ionization tandem mass spectrometry. Characteristic losses of a substituted phenylcarbinol and a benzaldehyde from the precursor ion were proposed to be derived from an ion-neutral complex (INC)-mediated competitive proton and hydride transfer reactions. The intermediacy of the INC consisting of a substituted benzyloxy anion and a phenyl isocyanate was supported by both ortho-site-blocking experiments and density functional theory calculations. Within the INC, the benzyloxy anion played the role of either a proton abstractor or a hydride donor toward its neutral counterpart. Relative abundances of the product ions were influenced by the nature of the substituents. Electron-withdrawing groups at the N-phenyl ring favored the hydrogen transfer process (including proton and hydride transfer), whereas electron-donating groups favored direct decomposition to generate the benzyloxy anion (or substituted benzyloxy anion). By contrast, electron-withdrawing and electron-donating substitutions at the O-benzyl ring exhibited opposite effects.
Collapse
Affiliation(s)
- Liqing Yao
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, Zhejiang, China
| | | | | | | |
Collapse
|
16
|
Yue L, Guo C, Chai Y, Yin X, Pan Y. Gas-phase reaction: alkyl cation transfer in the dissociation of protonated pyridyl carbamates in mass spectrometry. Tetrahedron 2014. [DOI: 10.1016/j.tet.2014.10.067] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
|
17
|
Shen S, Chai Y, Weng G, Pan Y. Intramolecular electrophilic aromatic substitution in gas-phase fragmentation of protonated N-benzylbenzaldimines. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:1662-1669. [PMID: 24957300 DOI: 10.1007/s13361-014-0935-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 05/21/2014] [Indexed: 06/03/2023]
Abstract
In this study, the gas-phase fragmentations of protonated N-benzylbenzaldimines were investigated by electrospray ionization tandem mass spectrometry (ESI-MS(n)). Upon collisional activation, several characteristic fragment ions are produced and their fragmentation mechanisms are rationalized by electrophilic aromatic substitution accompanied by benzyl cation transfer. (1) For N-(p-methoxybenzylidene)-1-phenylmethanimine, concomitant with a loss of HCN, a product ion at m/z 121 was observed. It is proposed to be generated from electrophilic substitution at the ipso-position by transferring benzyl cation rather than cleavage of the C-N double bond. (2) For N-(m-methoxybenzylidene)-1-phenylmethanimine, a product ion at m/z 209 was obtained, corresponding to the elimination of NH(3) carrying two hydrogens from the two aromatic rings respectively. This process can be rationalized by two sequential electrophilic substitutions and cyclodeamination reaction based on the benzyl cation transfer. Deuterium-labeled experiments, density functional theory (DFT) calculation and substituent effect results also corroborate the proposed mechanism.
Collapse
Affiliation(s)
- Shanshan Shen
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | | | | | | |
Collapse
|
18
|
Yue L, Wei W, Dang Q, Ding C, Pan Y. Negative charge induced dissociation: fragmentation of deprotonated N-benzylidene-2-hydroxylanilines in electrospray ionization mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2014; 49:579-584. [PMID: 25044842 DOI: 10.1002/jms.3376] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 04/01/2014] [Accepted: 04/14/2014] [Indexed: 06/03/2023]
Abstract
Unimolecular reactivities of different N-benzylidene-2-hydroxylaniline anions were investigated in gas phase by electrospray ionization tandem mass spectrometry. All the collision-induced dissociation spectra of N-benzylidene-2-hydroxylaniline anions show similar ions at phenyl anions, neutral loss of benzonitrile and benzoxazole anions, respectively. The possible fragmentation pathway was probed through deuterium labeling and various group substituents experiments. Computational results were applied to shed light on the mechanism of fragmentation patterns. The proton in the CH=N is reactive in the formation of the concerned ions. Its direct transfer to the oxygen results in 2-hydroxyphenyl anion. Proton abstraction between benzoxazole and phenyl anion leads to the formation of benzene and benzoxazole anion.
Collapse
Affiliation(s)
- Lei Yue
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
| | | | | | | | | |
Collapse
|
19
|
Guo ZQ, Qi HY, Jiang Y, Fang DM, Zhang GL, Wu ZJ. Analysis of a caffeic acid derivative by ESI-MS/MS: unexpected product ions formed by 'internal residue loss'. JOURNAL OF MASS SPECTROMETRY : JMS 2014; 49:428-431. [PMID: 24809905 DOI: 10.1002/jms.3352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 02/17/2014] [Accepted: 02/19/2014] [Indexed: 06/03/2023]
Affiliation(s)
- Ze-Qin Guo
- Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
| | | | | | | | | | | |
Collapse
|
20
|
Sun H, Wang L, Pan Y. Gas-phase arylmethyl transfer and cyclodeamination of argentinated N-arylmethyl-pyridin-2-ylmethanimine. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:169-175. [PMID: 24356863 DOI: 10.1007/s13361-013-0778-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 10/16/2013] [Accepted: 10/23/2013] [Indexed: 06/03/2023]
Abstract
In collisional activation of argentinated N-arylmethyl-pyridin-2-ylmethanimine, a neutral molecule of AgNH2 is eliminated, carrying one hydrogen from the methylene and the other one from the ortho position (relative to the ipso carbon) of the aryl ring. Taking argentinated N-benzyl-pyridin-2-ylmethanimine for example, the proposition that the AgNH2 loss results from intramolecular arylmethyl transfer combined with cyclodeamination is rationalized by deuterium labeling experiments, blocking experiments, and theoretical calculations. The structure of the final product ion from loss of AgNH2 was confirmed further by multistage mass spectrometry.
Collapse
Affiliation(s)
- Hezhi Sun
- Department of Chemistry, Zhejiang University, 38 Zheda Road, Hangzhou, 310027, China
| | | | | |
Collapse
|
21
|
Li F, Zhang X, Zhang H, Jiang K. Gas-phase fragmentation of the protonated benzyl ester of proline: intramolecular electrophilic substitution versus hydride transfer. JOURNAL OF MASS SPECTROMETRY : JMS 2013; 48:423-429. [PMID: 23584935 DOI: 10.1002/jms.3162] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 12/11/2012] [Accepted: 12/19/2012] [Indexed: 06/02/2023]
Abstract
In this study, the gas phase chemistry of the protonated benzyl esters of proline has been investigated by electrospray ionization mass spectrometry and theoretical calculation. Upon collisional activation, the protonated molecules undergo fragmentation reactions via three primary channels: (1) direct decomposition to the benzyl cation (m/z 91), (2) formation of an ion-neutral complex of [benzyl cation + proline](+), followed by a hydride transfer to generate the protonated 4,5-dihydro-3H-pyrrole-2-carboxylic acid (m/z 114), and (3) electrophilic attack at the amino by the transferring benzyl cation, and the subsequent migration of the activated amino proton leading to the simultaneous loss of (H2O + CO). Interestingly, no hydrogen/deuterium exchange for the fragment ion m/z 114 occurs in the d-labeling experiments, indicating that the transferring hydride in path-b comes from the methenyl hydrogen rather than the amino hydrogen. For para-substituted benzyl esters, the presence of electron-donating substituents significantly promotes the direct decomposition (path-a), whereas the presence of electron-withdrawing ones distinctively inhibits that channel. For the competing channels of path-b and path-c, the presence of electron-donating substituents favors path-b rather than path-c, whereas the presence of electron-withdrawing ones favors path-c rather than path-b.
Collapse
Affiliation(s)
- Fei Li
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 310012, China
| | | | | | | |
Collapse
|
22
|
Guo C, Yue L, Guo M, Jiang K, Pan Y. Elimination of benzene from protonated N-benzylindoline: benzyl cation/proton transfer or direct proton transfer? JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2013; 24:381-387. [PMID: 23361371 DOI: 10.1007/s13361-012-0561-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 12/06/2012] [Accepted: 12/07/2012] [Indexed: 06/01/2023]
Abstract
Collision-induced dissociation (CID) of protonated N-benzylindoline and its derivatives was investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS). Elimination of benzene was observed besides hydride transfer and electron transfer reactions. D-labeling experiments and accurate mass determinations of the product ions confirm that the external proton is retained in the fragment ion, and the elimination reaction was proposed to be initiated by benzyl cation transfer rather than proton transfer. Benzyl cation transfer from the nitrogen atom to one of the sp(2)-hybridized carbon atoms in the indoline core is the key step, and subsequent proton transfer reaction leads to the elimination of benzene. Density functional theory (DFT)-based calculations were performed and the computational results also support the benzyl cation/proton transfer mechanism. Figure ᅟ
Collapse
Affiliation(s)
- Cheng Guo
- Department of Chemistry, Zhejiang University, Hangzhou, China
| | | | | | | | | |
Collapse
|