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Zubčić G, You J, Zott FL, Ashirbaev SS, Kolympadi Marković M, Bešić E, Vrček V, Zipse H, Šakić D. Regioselective Rearrangement of Nitrogen- and Carbon-Centered Radical Intermediates in the Hofmann-Löffler-Freytag Reaction. J Phys Chem A 2024; 128:2574-2583. [PMID: 38516723 PMCID: PMC11000220 DOI: 10.1021/acs.jpca.3c07892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 03/06/2024] [Accepted: 03/06/2024] [Indexed: 03/23/2024]
Abstract
The Hofmann-Löffler-Freytag (HLF) reaction serves as a late-stage functionalization technique for generating pyrrolidine heterocyclic ring systems. Contemporary HLF protocols utilize in situ halogenated sulfonamides as precursors in the radical-mediated rearrangement cycle. Despite its well-established reaction mechanism, experiments toward the detection of radical intermediates using EPR techniques have only recently been attempted. However, the obtained spectra lack the distinct features of the N-centered radicals expected for the employed reactants. This paper presents phenylbutylnitrone spin-trapped C-centered and N-centered radicals, generated via light irradiation from N-halogen-tosyl-sulfonamide derivatives and detected using EPR spectroscopy. NMR spectroscopy and DFT calculations are used to explain the observed regioselectivity of the HLF reaction.
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Affiliation(s)
- Gabrijel Zubčić
- Faculty
of Pharmacy and Biochemistry, University
of Zagreb, Ante Kovačića 1, 10000 Zagreb, Croatia
| | - Jiangyang You
- Division
of Physical Chemistry, Rud̵er Bošković
Institute, Bijenička Cesta 54, 10000 Zagreb, Croatia
| | - Fabian L. Zott
- Department
of Chemistry, Ludwig-Maximilians-Universität
München, Butenandtstrasse 5-13, D-81377 München, Germany
| | - Salavat S. Ashirbaev
- Department
of Chemistry, Ludwig-Maximilians-Universität
München, Butenandtstrasse 5-13, D-81377 München, Germany
| | - Maria Kolympadi Marković
- Faculty
of Physics, and Centre for Micro- and Nanosciences and Technologies, University of Rijeka, Radmile Matejčić 2, 51000 Rijeka, Croatia
| | - Erim Bešić
- Faculty
of Pharmacy and Biochemistry, University
of Zagreb, Ante Kovačića 1, 10000 Zagreb, Croatia
| | - Valerije Vrček
- Faculty
of Pharmacy and Biochemistry, University
of Zagreb, Ante Kovačića 1, 10000 Zagreb, Croatia
| | - Hendrik Zipse
- Department
of Chemistry, Ludwig-Maximilians-Universität
München, Butenandtstrasse 5-13, D-81377 München, Germany
| | - Davor Šakić
- Faculty
of Pharmacy and Biochemistry, University
of Zagreb, Ante Kovačića 1, 10000 Zagreb, Croatia
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Thermal unimolecular reactivity pathways in dehydro‐diazines radicals. J PHYS ORG CHEM 2020. [DOI: 10.1002/poc.4152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Abstract
Radical stabilization energies (RSEs) for a wide variety of nitrogen-centered radicals and their protonated counterparts have been calculated at G3(MP2)-RAD and G3B3 level. The calculated RSE values can be rationalized through the combined effects of resonance delocalization of the unpaired spin, electron donation through adjacent alkyl groups or lone pairs, and through inductive electron donation/electron withdrawal. The influence of ring strain effects as well as the synergistic combination of individual substituent effects (captodatively stabilized N-radicals) have also been explored. In symmetric N-radicals the substituents may also affect the relative ordering of electronic states. In most cases the π-type radical (unpaired spin distribution perpendicular to the plane of the N-radical) is found to be most stable. Closed shell precursors of biological and pharmaceutical relevance, for which neither experimental nor theoretical results on radical stabilities exist, have been included.
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Affiliation(s)
- Johnny Hioe
- Department of Chemistry, LMU München, Butenandtstrasse 5-13, D-81377 München, Germany.
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Marenich AV, Ho J, Coote ML, Cramer CJ, Truhlar DG. Computational electrochemistry: prediction of liquid-phase reduction potentials. Phys Chem Chem Phys 2014; 16:15068-106. [PMID: 24958074 DOI: 10.1039/c4cp01572j] [Citation(s) in RCA: 314] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
This article reviews recent developments and applications in the area of computational electrochemistry. Our focus is on predicting the reduction potentials of electron transfer and other electrochemical reactions and half-reactions in both aqueous and nonaqueous solutions. Topics covered include various computational protocols that combine quantum mechanical electronic structure methods (such as density functional theory) with implicit-solvent models, explicit-solvent protocols that employ Monte Carlo or molecular dynamics simulations (for example, Car-Parrinello molecular dynamics using the grand canonical ensemble formalism), and the Marcus theory of electronic charge transfer. We also review computational approaches based on empirical relationships between molecular and electronic structure and electron transfer reactivity. The scope of the implicit-solvent protocols is emphasized, and the present status of the theory and future directions are outlined.
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Affiliation(s)
- Aleksandr V Marenich
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, 207 Pleasant Street S.E., Minneapolis, MN 55455-0431, USA.
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Vankayala SL, Hargis JC, Woodcock HL. How does catalase release nitric oxide? A computational structure-activity relationship study. J Chem Inf Model 2013; 53:2951-61. [PMID: 24087936 DOI: 10.1021/ci400395c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydroxyurea (HU) is the only FDA approved medication for treating sickle cell disease in adults. The primary mechanism of action is pharmacological elevation of nitric oxide (NO) levels which induces propagation of fetal hemoglobin. HU is known to undergo redox reactions with heme based enzymes like hemoglobin and catalase to produce NO. However, specific details about the HU based NO release remain unknown. Experimental studies indicate that interaction of HU with human catalase compound I produces NO. Presently, we combine flexible receptor-flexible substrate induced fit docking (IFD) with energy decomposition analyses to examine the atomic level details of a possible key step in the clinical conversion of HU to NO. Substrate binding modes of nine HU analogs with catalase compound I were investigated to determine the essential properties necessary for effective NO release. Three major binding orientations were found that provide insight into the possible reaction mechanisms for producing NO. Further results show that anion/radical intermediates produced as part of these mechanisms would be stabilized by hydrogen bonding interactions from distal residues His75, Asn148, Gln168, and oxoferryl-heme. These details will ideally contribute to both a clearer mechanistic picture and provide insights for future structure based drug design efforts.
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Affiliation(s)
- Sai Lakshmana Vankayala
- Department of Chemistry, University of South Florida , 4202 E. Fowler Avenue, CHE205, Tampa, Florida 33620-5250, United States
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