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Harariya MS, Gogoi R, Goswami A, Sharma AK, Jindal G. Is Enol Always the Culprit? The Curious Case of High Enantioselectivity in a Chiral Rh(II) Complex Catalyzed Carbene Insertion Reaction. Chemistry 2023; 29:e202301910. [PMID: 37665257 DOI: 10.1002/chem.202301910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 09/04/2023] [Accepted: 09/04/2023] [Indexed: 09/05/2023]
Abstract
The mechanism of Rh2 (S-NTTL)4 catalyzed carbene insertion into C(3)-H of indole is investigated using DFT methods. Since the commonly accepted enol mechanism cannot account for enantioinduction, a concerted oxocarbenium pathway was proposed in an earlier work using a model catalyst. However, after considering the full catalytic system, this study finds that akin to other reactions, here, too, the enol pathway is of lower energy, which now naturally raises a conundrum regarding the mode of chiral induction. Herein, a new water promoted mechanistic pathway involving a metal-associated enol intermediate hydrogen bonding and stereochemical model are proposed to solve this puzzle. It is shown how the catalyst bowl-shaped structure along with substrate-catalyst binding is crucial for achieving high levels of enantioselectivity. A stereodetermining water-assisted proton transfer is proposed and confirmed through deuterium-labeling experiments. The water molecules are held together by H-bonding interactions with the carboxylate ligands that is reminiscent of enzyme catalysis. Although several previous studies have aimed at understanding the mechanism of metal catalyzed carbene insertion reactions, the origin of high stereoinduction especially with chiral metal complexes remains unclear, and till date there is no transition state model that can explain the high enantioselectivity with such chiral Rh complexes. The metal-associated enol pathway is currently underrepresented in catalytic cycles and may play a crucial role in catalyst design. Since the enol pathway is commonly adopted in other metal-catalyzed X-H insertion reactions involving a diazoester, the presented results are not specific to the current reaction. Therefore, this study could provide the direction for achieving high levels of enantioselectivity which is otherwise difficult to achieve with a single metal catalyst.
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Affiliation(s)
- Mahesh S Harariya
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka, 560012, India
| | - Romin Gogoi
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka, 560012, India
| | - Anubhav Goswami
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka, 560012, India
| | - Akhilesh K Sharma
- Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans, 1643007, Tarragona, 560012, Spain
| | - Garima Jindal
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka, 560012, India
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2
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Singh Chauhan AN, Mali G, Dua G, Samant P, Kumar A, Erande RD. [RhCp*Cl 2] 2-Catalyzed Indole Functionalization: Synthesis of Bioinspired Indole-Fused Polycycles. ACS OMEGA 2023; 8:27894-27919. [PMID: 37576617 PMCID: PMC10413382 DOI: 10.1021/acsomega.3c02510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 07/11/2023] [Indexed: 08/15/2023]
Abstract
Polycyclic fused indoles are ubiquitous in natural products and pharmaceuticals due to their immense structural diversity and biological inference, making them suitable for charting broader chemical space. Indole-based polycycles continue to be fascinating as well as challenging targets for synthetic fabrication because of their characteristic structural frameworks possessing biologically intriguing compounds of both natural and synthetic origin. As a result, an assortment of new chemical processes and catalytic routes has been established to provide unified access to these skeletons in a very efficient and selective manner. Transition-metal-catalyzed processes, in particular from rhodium(III), are widely used in synthetic endeavors to increase molecular complexity efficiently. In recent years, this has resulted in significant progress in reaching molecular scaffolds with enormous biological activity based on core indole skeletons. Additionally, Rh(III)-catalyzed direct C-H functionalization and benzannulation protocols of indole moieties were one of the most alluring synthetic techniques to generate indole-fused polycyclic molecules efficiently. This review sheds light on recent developments toward synthesizing fused indoles by cascade annulation methods using Rh(III)-[RhCp*Cl2]2-catalyzed pathways, which align with the comprehensive and sophisticated developments in the field of Rh(III)-catalyzed indole functionalization. Here, we looked at a few intriguing cascade-based synthetic designs catalyzed by Rh(III) that produced elaborate frameworks inspired by indole bioactivity. The review also strongly emphasizes mechanistic insights for reaching 1-2, 2-3, and 3-4-fused indole systems, focusing on Rh(III)-catalyzed routes. With an emphasis on synthetic efficiency and product diversity, synthetic methods of chosen polycyclic carbocycles and heterocycles with at least three fused, bridged, or spiro cages are reviewed. The newly created synthesis concepts or toolkits for accessing diazepine, indol-ones, carbazoles, and benzo-indoles, as well as illustrative privileged synthetic techniques, are included in the featured collection.
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Affiliation(s)
| | - Ghanshyam Mali
- Department
of Chemistry, Indian Institute of Technology
Jodhpur, Jodhpur 342037, India
| | - Garima Dua
- Department
of Chemistry, Indian Institute of Technology
Jodhpur, Jodhpur 342037, India
| | - Priya Samant
- Department
of Chemistry, Indian Institute of Technology
Jodhpur, Jodhpur 342037, India
| | - Akhilesh Kumar
- Department
of Chemistry and Nano Science, Ewha Womans
University, Seoul 03760, Korea
| | - Rohan D. Erande
- Department
of Chemistry, Indian Institute of Technology
Jodhpur, Jodhpur 342037, India
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3
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He J, Liu A, Yu Y, Wang C, Mei H, Han J. Electrochemical Annulation of Indole-Tethered Alkynes Enabling Synthesis of Exocyclic Alkenyl Tetrahydrocarbazoles. J Org Chem 2023. [PMID: 37216919 DOI: 10.1021/acs.joc.3c00267] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
An electrochemical sulfonylation-triggered cyclization reaction of indole-tethered terminal alkynes with sulfinates as sulfonyl sources has been developed, which affords exocyclic alkenyl tetrahydrocarbazoles in good chemical yields. This reaction features convenient operation and tolerates a wide scope of substrates with a variety of electronically and sterically diverse substituents. Furthermore, high E-stereoselectivity is observed for this reaction, which provides an efficient method for the preparation of functionalized tetrahydrocarbazole derivatives.
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Affiliation(s)
- Jingrui He
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Aiyao Liu
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Yingjie Yu
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Chengting Wang
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Haibo Mei
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Jianlin Han
- Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
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4
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Zhang YB, Li BS, Xu GJ, Sun W, Sun M. Rh(III)-Catalyzed Double C-H Functionalization of Indoles with Cyclopropenones via Sequential C-H/C-C/C-H Bond Activation. Org Lett 2023. [PMID: 37200408 DOI: 10.1021/acs.orglett.3c01292] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
An unprecedented Rh(III)-catalyzed double C-H functionalization of indoles with cyclopropenones via sequential C-H/C-C/C-H bond activation has been developed. This procedure represents the first example for assembling of cyclopenta[b]indoles utilizing cyclopropenones as 3C synthons. This powerful approach shows excellent chemo- and regioselectivity, wide functional group tolerance, and good reaction yields.
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Affiliation(s)
- Yan-Bo Zhang
- Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an 710127, China
| | - Bin-Shi Li
- Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an 710127, China
| | - Guo-Jie Xu
- Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an 710127, China
| | - Wei Sun
- Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an 710127, China
| | - Meng Sun
- Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an 710127, China
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Recent Strategies in Transition-Metal-Catalyzed Sequential C–H Activation/Annulation for One-Step Construction of Functionalized Indazole Derivatives. Molecules 2022; 27:molecules27154942. [PMID: 35956893 PMCID: PMC9370621 DOI: 10.3390/molecules27154942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 07/28/2022] [Accepted: 07/29/2022] [Indexed: 11/17/2022] Open
Abstract
Designing new synthetic strategies for indazoles is a prominent topic in contemporary research. The transition-metal-catalyzed C–H activation/annulation sequence has arisen as a favorable tool to construct functionalized indazole derivatives with improved tolerance in medicinal applications, functional flexibility, and structural complexity. In the current review article, we aim to outline and summarize the most common synthetic protocols to use in the synthesis of target indazoles via a transition-metal-catalyzed C–H activation/annulation sequence for the one-step synthesis of functionalized indazole derivatives. We categorized the text according to the metal salts used in the reactions. Some metal salts were used as catalysts, and others may have been used as oxidants and/or for the activation of precatalysts. The roles of some metal salts in the corresponding reaction mechanisms have not been identified. It can be expected that the current synopsis will provide accessible practical guidance to colleagues interested in the subject.
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Balhara R, Jindal G. Does an Enol Pathway Preclude High Stereoselectivity in Iron-Catalyzed Indole C-H Functionalization via Carbene Insertion? J Org Chem 2022; 87:7919-7933. [PMID: 35652604 DOI: 10.1021/acs.joc.2c00573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
C-H functionalization of indoles via Fe carbenoids presents an attractive strategy to obtain biologically important structural motifs. However, obtaining good stereoselectivity with Fe has been a significant challenge. It is unclear whether the low selectivity is due to a radical pathway or an ionic mechanism involving metal-free species. We therefore present a density functional theory (DFT) study of indole alkylation with diazoacetates catalyzed by Fe(ClO4)TMEDA/spirobisoxazoline and myoglobin. We explore three mechanistic pathways: nucleophilic, radical, and oxocarbenium routes. The nucleophilic pathway is the most feasible with the formation of an enol species that tautomerizes to furnish the alkylated indole. While this mechanism is routinely proposed, the stereochemical model has been conspicuously absent until now. We show that the conventionally invoked enol pathway is not responsible for the low enantiomeric excess. The enol intermediate can stay coordinated to the catalyst via different binding sites placing the enol in proximity to the chiral environment and affecting the stereoselective proton transfer. Both the binding strength and the chiral environment are crucial for obtaining high selectivity. Our study provides the much needed insights for the modest-low selectivities of Fe systems and could help in expediting the discovery of an efficient catalytic system. These mechanistic underpinnings could also be applicable to other metal (Rh, Pd, Cu, etc.)-catalyzed X-H insertion reactions.
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Affiliation(s)
- Reena Balhara
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Garima Jindal
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka 560012, India
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7
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Wang Q, Shi Y, Huang X, Wang Y, Jiao J, Tang Y, Li J, Xu S, Li Y. Ru(II)-Catalyzed Difunctional Pyridyloxy-Directed Regio- and Stereospecific Addition of Carboxylic Acids to Internal Alkynes. Org Lett 2021; 24:379-384. [PMID: 34935395 DOI: 10.1021/acs.orglett.1c04052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A highly efficient Ru(II)-catalyzed regio- and stereospecific hydro-oxycarbonylation of unsymmetrical internal alkynes bearing a difunctional 2-pyridyloxy directing group with carboxylic acids has been developed, which provides allylic (Z)-enol esters in good to excellent yields with a broad substrate scope under mild conditions. The difunctional directing group can be diversely derivatized, particularly undergoing allylic substitution with various nucleophiles to afford β-functionalized (Z)-enol esters without directing groups.
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Affiliation(s)
- Qin Wang
- Department of Material Chemistry, School of Chemistry, and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Yan Shi
- Department of Material Chemistry, School of Chemistry, and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Xiaoli Huang
- Department of Material Chemistry, School of Chemistry, and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Yongzhuang Wang
- Department of Material Chemistry, School of Chemistry, and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Jiao Jiao
- Department of Material Chemistry, School of Chemistry, and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Yuhai Tang
- Department of Material Chemistry, School of Chemistry, and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Jing Li
- Department of Material Chemistry, School of Chemistry, and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Silong Xu
- Department of Material Chemistry, School of Chemistry, and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Yang Li
- Department of Material Chemistry, School of Chemistry, and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
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8
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Kim D, Yoo H, Park MH, Kim Y, Chuang GJ, Yoo K, Kim D, Kim HJ, Kim M. Transformation of
tert
‐Butyl Amide Directing Groups to Nitriles in Iridium‐Catalyzed C−H Bond Functionalizations. ASIAN J ORG CHEM 2021. [DOI: 10.1002/ajoc.202100641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Dopil Kim
- Department of Chemistry Chungbuk National University Cheongju 28644 Republic of Korea
| | - Haneul Yoo
- Department of Chemistry Chungbuk National University Cheongju 28644 Republic of Korea
| | - Myung Hwan Park
- Department of Chemistry Education Chungbuk National University Cheongju 28644 Republic of Korea
| | - Youngjo Kim
- Department of Chemistry Chungbuk National University Cheongju 28644 Republic of Korea
| | - Gary Jing Chuang
- Department of Chemistry Chung Yuan Christian University Taoyuan 32023 Taiwan
| | - Kwangho Yoo
- Inorganic Chemistry I Ruhr-Universitat Bochum Bochum 44780 Germany
| | - Dongwook Kim
- Center for Catalytic Hydrocarbon Functionalization Institute for Basic Science Daejeon 34141 Republic of Korea
| | - Hyun Jin Kim
- Innovative Therapeutic Research Center Therapeutics and Biotechnology Division Korea Research Institute of Chemical Technology (KRICT) Daejeon 34114 Republic of Korea
| | - Min Kim
- Department of Chemistry Chungbuk National University Cheongju 28644 Republic of Korea
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9
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Huang X, Shi Y, Wang Y, Jiao J, Tang Y, Li J, Xu S, Li Y. Synthesis of Indole-Fused Oxepines via C-H Activation Initiated Diastereoselective [5 + 2] Annulation of Indoles with 1,6-Enynes. Org Lett 2021; 23:8365-8369. [PMID: 34652931 DOI: 10.1021/acs.orglett.1c03106] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A rhodium-catalyzed diastereoselective formal [5 + 2] annulation of indoles with cyclohexadienone-containing 1,6-enynes has been established via indole 2,3-difunctionalization. The reaction, probably proceeding through tandem indole C2-H alkenylation and intramolecular Friedel-Crafts alkylation relay, provides rapid construction of indole-fused oxepines in good to excellent yields with a broad substrate scope. This method also features concomitant construction of cis-hydrobenzo[b] oxepine scaffolds, a core unit found in numerous natural products of important biological activities.
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Affiliation(s)
- Xiaoli Huang
- Department of Material Chemistry, School of Chemistry and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Yan Shi
- Department of Material Chemistry, School of Chemistry and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Yongzhuang Wang
- Department of Material Chemistry, School of Chemistry and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Jiao Jiao
- Department of Material Chemistry, School of Chemistry and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Yuhai Tang
- Department of Material Chemistry, School of Chemistry and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Jing Li
- Department of Material Chemistry, School of Chemistry and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Silong Xu
- Department of Material Chemistry, School of Chemistry and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Yang Li
- Department of Material Chemistry, School of Chemistry and Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University, Xi'an 710049, P. R. China
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10
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Wu M, Wang S, Wang Y, Gao H, Yi W, Zhou Z. TFA‐Prompted/Rh(III)‐Catalysed Chemoselective C
3
− or C
2
−H Functionalization of Indoles with Methylenecyclopropanes. European J Org Chem 2021. [DOI: 10.1002/ejoc.202101132] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Min Wu
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease School of Pharmaceutical Sciences & the Fifth Affiliated Hospital Guangzhou Medical University Guangzhou Guangdong 511436 P. R. China
| | - Shengdong Wang
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease School of Pharmaceutical Sciences & the Fifth Affiliated Hospital Guangzhou Medical University Guangzhou Guangdong 511436 P. R. China
| | - Yi Wang
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease School of Pharmaceutical Sciences & the Fifth Affiliated Hospital Guangzhou Medical University Guangzhou Guangdong 511436 P. R. China
| | - Hui Gao
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease School of Pharmaceutical Sciences & the Fifth Affiliated Hospital Guangzhou Medical University Guangzhou Guangdong 511436 P. R. China
| | - Wei Yi
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease School of Pharmaceutical Sciences & the Fifth Affiliated Hospital Guangzhou Medical University Guangzhou Guangdong 511436 P. R. China
| | - Zhi Zhou
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease School of Pharmaceutical Sciences & the Fifth Affiliated Hospital Guangzhou Medical University Guangzhou Guangdong 511436 P. R. China
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