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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.
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Li J, Pan Y, Chen B. The ion-neutral complex-mediated fragmentation reaction in electrospray ionization tandem mass spectrometric analysis of N-phenyl-3-(phenylthio)propanamides. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2022; 36:e9333. [PMID: 35705519 DOI: 10.1002/rcm.9333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 06/07/2022] [Accepted: 06/13/2022] [Indexed: 06/15/2023]
Abstract
RATIONALE Amides are the fundamental units of both peptides and proteins, and also important functional groups of medical chemicals. Investigation of the fragmentation mechanism of amides in the gas phase is scientifically important for structural analysis. However, understanding of this problem is still elusive. METHODS Protonated N-phenyl-3-(phenylthio)propanamide and its derivatives were investigated using positive ion tandem mass spectrometry (ESI-MS/MS) with an LCQ mass spectrometer. Accurate mass analysis was conducted with a micrOTOF-QII mass spectrometer. Density functional theory (DFT) calculations using the Gaussian 03 program and deuterium-labelling (D-labelling) experiments were performed to verify the proposed fragmentation mechanism. RESULTS Interpretation of the fragment ions in the collision-induced dissociation mass spectra showed that the ionizing proton in the protonated ion transferred from the most thermodynamically favorable carbonyl oxygen to the dissociative protonation site at amide nitrogen or sulfur atom upon collisional activation. The dissociation of the amide or the C-S bond was induced by such proton transfer. An ion-neutral complex (INC) was generated via the dissociation of the amide bond. In the INC, it was observed that the carbocation of the ionic part attacked the ortho phenyl carbon atom adjacent to the sulfur atom, and proton transfer from the carbon atom to the nitrogen atom led to the formation of protonated aniline. CONCLUSIONS The fragmentation mechanism of protonated N-phenyl-3-(phenylthio)propanamide and its derivatives was proposed and elucidated. All the compounds studied showed similar fragmentation pathways, and the competitive formation of two ions, RC9 H9 OS+ and C6 H8 N+ , was observed. The generation of protonated aniline is mediated by INC in ESI-MS/MS.
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Affiliation(s)
- Jing Li
- Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, Zhejiang, China
- Institute of Zhejiang University-Quzhou, Quzhou, Zhejiang, China
| | - Yuanjiang Pan
- Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang, China
| | - Bajin Chen
- Zhejiang Transfar Functional New Materials Co. Ltd, Hangzhou, Zhejiang, China
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3
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Li C, Kong Q, Mou H, Jiang Y, Du Y, Zhang F. Biotransformation of alkylamides and alkaloids by lactic acid bacteria strains isolated from Zanthoxylum bungeanum meal. BIORESOURCE TECHNOLOGY 2021; 330:124944. [PMID: 33735732 DOI: 10.1016/j.biortech.2021.124944] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 03/01/2021] [Accepted: 03/02/2021] [Indexed: 06/12/2023]
Abstract
Zanthoxylum bungeanum meal (ZBM) is the by-product of Z. bungeanum seeds after pressing. It is restricted as a feed additive because it contains stimulating and potentially harmful substances, which are alkylamides and alkaloids. This study described the use of Lactobacillus paracasei and L. acidipiscis isolated from ZBM in solid-state fermentation of ZBM to reduce the concentration of undesirable alkylamides and alkaloids. By optimizing the substrate and fermentation conditions, the minimum contents of alkylamide and alkaloid were 2.96 and 3.20 mg/g, and the degradation rates reached 51.86% and 39.59%, respectively. Moreover, the biotransformation pathways of hydroxyl-α-sanshool and chelerythrine were established by identifying the metabolites. Bacterial diversity was shift significantly, and the relative abundance of Lactobacillus increased from 0.10% to 99.0% after fermentation. In conclusion, this study introduced a reliable strategy for processing ZBM as a feed additive.
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Affiliation(s)
- Chenman Li
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, Shandong, China
| | - Qing Kong
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, Shandong, China.
| | - Haijin Mou
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, Shandong, China
| | - Yun Jiang
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, Shandong, China
| | - Yongli Du
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, Shandong, China
| | - Fang Zhang
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, Shandong, China
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Computer-Aided Design, Synthesis, and Antiviral Evaluation of Novel Acrylamides as Potential Inhibitors of E3-E2-E1 Glycoproteins Complex from Chikungunya Virus. Pharmaceuticals (Basel) 2020; 13:ph13070141. [PMID: 32629969 PMCID: PMC7407227 DOI: 10.3390/ph13070141] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 06/23/2020] [Accepted: 06/25/2020] [Indexed: 02/07/2023] Open
Abstract
Chikungunya virus (CHIKV) causes an infectious disease characterized by inflammation and pain of the musculoskeletal tissues accompanied by swelling in the joints and cartilage damage. Currently, there are no licensed vaccines or chemotherapeutic agents to prevent or treat CHIKV infections. In this context, our research aimed to explore the potential in vitro anti-CHIKV activity of acrylamide derivatives. In silico methods were applied to 132 Michael’s acceptors toward the six most important biological targets from CHIKV. Subsequently, the ten most promising acrylamides were selected and synthesized. From the cytotoxicity MTT assay, we verified that LQM330, 334, and 336 demonstrate high cell viability at 40 µM. Moreover, these derivatives exhibited anti-CHIKV activities, highlighting the compound LQM334 which exhibited an inhibition value of 81%. Thus, docking simulations were performed to suggest a potential CHIKV-target for LQM334. It was observed that the LQM334 has a high affinity towards the E3-E2-E1 glycoproteins complex. Moreover, LQM334 reduced the percentage of CHIKV-positive cells from 74.07 to 0.88%, 48h post-treatment on intracellular flow cytometry staining. In conclusion, all virtual simulations corroborated with experimental results, and LQM334 could be used as a promising anti-CHIKV scaffold for designing new drugs in the future.
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Krauß J, Klimt M, Luber M, Mayer P, Bracher F. Characterization of two new degradation products of atorvastatin calcium formed upon treatment with strong acids. Beilstein J Org Chem 2019; 15:2085-2091. [PMID: 31579096 PMCID: PMC6753681 DOI: 10.3762/bjoc.15.206] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 08/22/2019] [Indexed: 12/02/2022] Open
Abstract
Atorvastatin calcium (Lipitor®, Sortis®) is a well-established cholesterol synthesis enzyme (CSE) inhibitor commonly used in the therapy of hypercholesterolemia. This drug is known to be sensitive to acid treatment, but only little data has been published on the structures of the degradation products. Here we report the identification of two novel degradation products of atorvastatin, which are formed only under drastic acidic conditions. While treatment with conc. sulfuric acid led to a loss of the carboxanilide residue (accompanied by an expectable lactonization/dehydration process in the side chain), treatment with conc. aqueous hydrochloric acid gave a complex, bridged molecule under C–C-bond formation of the lactone moiety with the pyrrole, migration of the isopropyl group and loss of the carboxanilide residue. The novel degradation products were characterized by NMR spectroscopy, HRMS data and X-ray crystal structure analysis.
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Affiliation(s)
- Jürgen Krauß
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians University Munich, Butenandtstr. 5-13, 81377 Munich, Germany
| | - Monika Klimt
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians University Munich, Butenandtstr. 5-13, 81377 Munich, Germany
| | - Markus Luber
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians University Munich, Butenandtstr. 5-13, 81377 Munich, Germany
| | - Peter Mayer
- Department of Chemistry, Ludwig-Maximilians University Munich, Butenandtstr. 5-13, 81377 Munich, Germany
| | - Franz Bracher
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians University Munich, Butenandtstr. 5-13, 81377 Munich, Germany
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Zhang X, Cheng S. Intramolecular Halogen Atom Coordinated H Transfer via Ion-Neutral Complex in the Gas Phase Dissociation of Protonated Dichlorvos Derivatives. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:2246-2254. [PMID: 28681359 DOI: 10.1007/s13361-017-1736-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2017] [Revised: 05/25/2017] [Accepted: 06/08/2017] [Indexed: 06/07/2023]
Abstract
Intramolecular halogen atom coordinated H transfer reaction in the gas phase dissociation of protonated dichlorvos derivatives has been explored by electrospray ionization tandem mass spectrometry. Upon collisional activation, protonated dichlorvos underwent dissociation reaction via cleavage of the P-O bond to give reactive ion-neutral complex (INC) intermediate, [dimethoxylphosphinoylium + dichloroacetaldehyde]. Besides direct dissociation of the complex, intramolecular chlorine atom coordinated H transfer reaction within the complex takes place, leading to the formation of protonated dimethyl chlorophosphate. To investigate the fragmentation mechanism, deuterium-labeled experiments and several other halogen-substituted (Br and F) analogs of dichlorvos were prepared and evaluated, which display a similar intramolecular halogen transfer. Density functional theory (DFT)-based calculations were performed and the computational results also support the mechanism. Graphical Abstract ᅟ.
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Affiliation(s)
- Xiaoping Zhang
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang, 330013, People's Republic of China.
| | - Shuai Cheng
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang, 330013, People's Republic of China
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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.
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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
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Guo M, Yin D, Han J, Li X, Zhang L, Du Y, Wang H, Guo C, Tang D. Investigation of the formation of the [2(iohexol) + Mg] 2+ complex and its fragmentation in electrospray ionization tandem mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2017; 31:9-15. [PMID: 27747964 DOI: 10.1002/rcm.7765] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Revised: 08/29/2016] [Accepted: 10/13/2016] [Indexed: 06/06/2023]
Abstract
RATIONALE Mass spectrometry has been developed as one of the common tools for the analysis of the organometallic systems in the gas phase over decades. The study of the fragmentation of organics-metal complexes has attracted much attention since the interesting dissociation pathways exhibited by these compounds are usually different from the protonated analogues. METHODS In this work, iohexol complexed with different dications such as Mg2+ , Cu2+ and Zn2+ have been investigated by electrospray ionization (ESI) tandem mass spectrometry. Additionally, deuterium-labeling experiments and an analogue of iohexol were utilized to confirm the reaction mechanisms. A computational chemistry method was used to identify the coordination conformation between iohexol and metal ions in the gas phase. UV detection was also used to identify the interaction between iohexol and metal ions in the liquid phase. RESULTS A special gas-phase open-loop reaction of iohexol induced by Mg2+ , leading to the formation of [iohexol + Mg - H - HI - C3 H4 O]+ , was observed in the collision-induced dissociation of [2(iohexol) + Mg]2+ complexes. Moreover, theoretical calculation shows the proposed coordination configuration of iohexol/Mg2+ complexes. The Mg2+ could have tetrahedral coordination with two iohexol molecules. CONCLUSIONS The percent study is a case for better understanding the formation of a typical organic/metal complex and its gas-phase fragmentation reaction. In addition, it provides useful information for researchers working on analysis or structural elucidation of complicated compounds which contain the iohexol analogues. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Mengzhe Guo
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical College, Xuzhou, Jiangsu, 221004, China
| | - Dengyang Yin
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical College, Xuzhou, Jiangsu, 221004, China
| | - Jie Han
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical College, Xuzhou, Jiangsu, 221004, China
| | - Xiao Li
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical College, Xuzhou, Jiangsu, 221004, China
| | - Liyan Zhang
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical College, Xuzhou, Jiangsu, 221004, China
| | - Yan Du
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical College, Xuzhou, Jiangsu, 221004, China
| | - Haibo Wang
- Cardiovascular Division, Xuzhou Central Hospital, Xuzhou, Jiangsu, 221000, China
| | - Cheng Guo
- Cancer Institute, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China
| | - Daoquan Tang
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical College, Xuzhou, Jiangsu, 221004, China
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Wang S, Dong C, Yu L, Guo C, Jiang K. Dissociation of protonated N-(3-phenyl-2H-chromen-2-ylidene)-benzenesulfonamide in the gas phase: cyclization via sulfonyl cation transfer. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:95-100. [PMID: 26661975 DOI: 10.1002/rcm.7420] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 09/23/2015] [Accepted: 10/05/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE In the tandem mass spectrometry of protonated N-(3-phenyl-2H-chromen-2-ylidene)benzenesulfonamides, the precursor ions have been observed to undergo gas-phase dissociation via two competing channels: (a) the predominant channel involves migration of the sulfonyl cation to the phenyl C atom and the subsequent loss of benzenesulfinic acid along with cyclization reaction, and (b) the minor one involves dissociation of the precursor ion to give an ion/neutral complex of [sulfonyl cation/imine], followed by decomposition to afford sulfonyl cation or the INC-mediated electron transfer to give an imine radical cation. METHODS The proposed reaction channels have been supported by theoretical calculations and D-labeling experiments. RESULTS The gas-phase cyclization reaction originating from the N- to C-sulfonyl cation transfer has been first reported to the best of our knowledge. CONCLUSIONS For the substituted sulfonamides, the presence of electron-donating groups (R(2) -) at the C-ring effectively facilitates the reaction channel of cyclization reaction, whereas that of electron-withdrawing groups inhibits this pathway.
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Affiliation(s)
- Shanshan Wang
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China
| | - Cheng Dong
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China
| | - Lian Yu
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China
| | - Cheng Guo
- Cancer Institute, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310009, China
| | - Kezhi Jiang
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China
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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.
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Affiliation(s)
- Shanshan Shen
- Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
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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.
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Affiliation(s)
- Liqing Yao
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, Zhejiang, China
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Guo M, Pan Y, Zhang R, Cao Y, Chen J, Pan Y. The specific cleavage of lactone linkage to open-loop in cyclic lipopeptide during negative ESI tandem mass spectrometry: the hydrogen bond interaction effect of 4-ethyl guaiacol. PLoS One 2014; 9:e104835. [PMID: 25144459 PMCID: PMC4140680 DOI: 10.1371/journal.pone.0104835] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 07/13/2014] [Indexed: 11/27/2022] Open
Abstract
Mass spectrometry is a valuable tool for the analysis and identification of chemical compounds, particularly proteins and peptides. Lichenysins G, the major cyclic lipopeptide of lichenysin, and the non-covalent complex of lichenysins G and 4-ethylguaiacol were investigated with negative ion ESI tandem mass spectrometry. The different fragmentation mechanisms for these compounds were investigated. Our study shows the 4-ethylguaiacol hydrogen bond with the carbonyl oxygen of the ester group in the loop of lichenysins G. With the help of this hydrogen bond interaction, the ring structure preferentially opens in lactone linkage rather than O-C bond of the ester-group to produce alcohol and ketene. Isothermal titration 1H-NMR analysis verified the hydrogen bond and determined the proportion of subject and ligand in the non-covalent complex to be 1∶1. Theoretical calculations also suggest that the addition of the ligand can affect the energy of the transition structures (TS) during loop opening.
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Affiliation(s)
- Mengzhe Guo
- Department of Chemistry, Zhejiang University, Hangzhou, China
| | - Youlu Pan
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Rong Zhang
- School of Biotechnology, Jiangnan University, Wuxi, China
| | - Yang Cao
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Jianzhong Chen
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Yuanjiang Pan
- Department of Chemistry, Zhejiang University, Hangzhou, China
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Guo C, Jiang K, Zheng S. Fragmentation reactions of N-benzyltetrahydroquinolines in electrospray ionization mass spectrometry: the roles of ion/neutral complex intermediates. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2014; 28:1381-1386. [PMID: 24797950 DOI: 10.1002/rcm.6918] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2014] [Revised: 04/06/2014] [Accepted: 04/07/2014] [Indexed: 06/03/2023]
Abstract
RATIONALE Electrospray ionization mass spectrometry (ESI-MS) combined with the collision-induced dissociation (CID) technique has assumed increasing importance as an invaluable tool for the structural analysis of organic and biological molecules. However, general rules for elucidating the fragmentation behaviors of charged molecules in the gas phase are still lacking. Therefore, explorations on the mechanistic information are desirable at all times. METHODS CID experiments of protonated N-benzyltetrahydroquinolines were carried out on ESI ion trap mass spectrometer and accurate mass measurements were performed on a high-resolution ESI quadrupole time-of-flight (Q-TOF) mass spectrometer in positive ion mode. RESULTS An ion/neutral complex, [RC6H4CH2(+)/tetrahydroquinoline], resulting from cleavage of the C-N bond induced by the positive charge brought in by protonation, was proposed to be the intermediate to elucidate the fragmentation reactions. For all the compounds investigated, benzyl cation transfer, electron transfer and hydride transfer reactions mediated by the complex were observed. Moreover, for the compound substituted by a methyl group at the para-position of the benzylic phenyl ring, proton transfer reaction via the complex also occurs. CONCLUSIONS This study is a case for better understanding the intriguing roles of ion/neutral complexes in gas-phase fragmentation reactions and enriching the knowledge about the gas-phase chemistry of the benzyl cation. In addition, it provides useful information for researchers working on analysis or structural elucidation of complicated compounds which contain the N-benzyltetrahydroquinoline substructure.
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Affiliation(s)
- Cheng Guo
- Cancer Institute (Key Laboratory of Cancer Prevention and Intervention, China National Ministry of Education, Key Laboratory of Molecular Biology in Medical Sciences, Zhejiang Province, China), The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310009, China
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Kumar V, Kumar S, Singh B, Kumar N. Quantitative and structural analysis of amides and lignans in Zanthoxylum armatum by UPLC-DAD-ESI-QTOF–MS/MS. J Pharm Biomed Anal 2014; 94:23-9. [DOI: 10.1016/j.jpba.2014.01.028] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 01/14/2014] [Accepted: 01/21/2014] [Indexed: 10/25/2022]
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Guo M, Guo C, Pan Y. Competitive formation of b2 and c2-H2O ions from b3 ions containing Asp residue during tandem mass spectrometry: the influence of neighboring Arg. Amino Acids 2014; 46:1939-46. [DOI: 10.1007/s00726-014-1743-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 04/04/2014] [Indexed: 11/28/2022]
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Lu Z, Chai Y, Guo C, Sun C, Pan Y. H2O loss in the fragmentation of deprotonated N-o-tolylamides in tandem mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2013; 48:1010-1014. [PMID: 24078241 DOI: 10.1002/jms.3257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Revised: 07/13/2013] [Accepted: 07/16/2013] [Indexed: 06/02/2023]
Affiliation(s)
- Zhihua Lu
- Department of Chemistry, Zhejiang University, Hangzhou, 310027, China
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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
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Affiliation(s)
- Cheng Guo
- Department of Chemistry, Zhejiang University, Hangzhou, China
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18
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You Z, Guo C, Pan Y. An experimental and theoretical study on fragmentation of protonated N-(2-pyridinylmethyl)indole in electrospray ionization mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2012; 26:2509-2516. [PMID: 23008068 DOI: 10.1002/rcm.6371] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
RATIONALE The dissociation reactions of protonated molecules are the base of structural analysis in electrospray ionization tandem mass spectrometry (ESI-MS(n)). However, general rules for elucidating the numerous fragmentation reactions in ESI-MS(n) are still rather lacking. Therefore, it is very important at all times to carry out mechanistic investigations for fragmentation reactions in the gas phase. METHODS The fragmentation reactions of protonated N-(2-pyridinylmethyl)indoles were studied by both of ESI ion trap tandem mass spectrometry and ESI Fourier transform ion cyclotron resonance tandem mass spectrometry in positive-ion mode. RESULTS In ESI-MS/MS, the ionizing proton is first bound to the most thermodynamically favored site, the pyridine nitrogen; then it transfers to the dissociative protonation sites and triggers the fragmentation. In the fragmentation of the target compounds, some interesting reactions, such as rearrangement, proton transfer and electron transfer reactions, take place via ion/neutral complexes. The proposed mechanisms are supported by both theoretical calculations and isotopic labeling experiments. CONCLUSIONS This study is a case for better understanding the dissociative protonation sites and enriching the knowledge about the role of ion/neutral complexes in ESI-MS. It also provides useful information for the structural analysis of organic compounds, especially drug analysis in pharmaceutical chemistry.
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Affiliation(s)
- Zhushuang You
- Department of Chemistry, Zhejiang University, Hangzhou, China
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