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Markham GD, Rostami H, Larkin JD, Bock CW. Models for boronic acid receptors II: a computational structural, bonding, and thermochemical investigation of the RB(OH)2∙H2O∙NH3 and RB(−OCH2CH2O−)∙NH3∙H2O potential energy surfaces (R = H, methyl, phenyl, and ortho-methyl-phenyl). Struct Chem 2023. [DOI: 10.1007/s11224-023-02131-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
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Markham GD, Larkin JD, Bock CW. Models for boronic acid receptors: a computational structural, bonding, and thermochemical investigation of the HB(OH)2∙H2O∙NH3 and HB(-O-CH2-CH2-O-)∙NH3∙H2O potential energy surfaces. Struct Chem 2021. [DOI: 10.1007/s11224-020-01701-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Larkin JD, Bock CW. A comparison of the structure and bonding in the donor–acceptor complexes H3N → BR(OH)2 and H3N → BRH(OH) (R = H; NH2, OH, and F): a computational investigation. Struct Chem 2019. [DOI: 10.1007/s11224-018-1205-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Rao NZ, Larkin JD, Bock CW. Monosubstituted Phenylboronic Acids, R-B(OH) 2 (R = C 6H 5, C 6H 4CH 3, C 6H 4NH 2, C 6H 4OH, and C 6H 4F): A Computational Investigation. Struct Chem 2017; 28:945-955. [PMID: 29375238 PMCID: PMC5784759 DOI: 10.1007/s11224-016-0897-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 12/04/2016] [Indexed: 01/05/2023]
Abstract
Phenylboronic acids (PBAs) are an important class of compounds with diverse applications in synthetic, biological, medicinal, and materials chemistry. In this investigation we report structural and thermochemical parameters for several monosubstituted ortho, meta, and para PBAs, R-B(OH)2 (R = C6H5, C6H4CH3, C6H4NH2, C6H4OH, and C6H4F). Equilibrium geometries of all the PBAs discussed in this article were obtained using second-order Møller-Plesset perturbation theory (MP2) with the Dunning-Woon aug-cc-pVDZ basis set; heats of formation (HOF) were calculated at the Gaussian-3 (G3) level of theory. The endo-exo conformers of all the positional isomers of these PBAs were lowest in energy. Using HOF for the monosubstituted PBAs calculated at the G3 level of theory, in conjunction with the experimental HOF for benzene, toluene, aniline, phenol, and fluorobenzene, the values of [Formula: see text] for the transfer processes C6H6 + C6H4X-B(OH)2 → C6H5X + C6H5-B(OH)2 (X = CH3, NH2, OH, and F) are found to be in good agreement with values of [Formula: see text] calculated at the MP2(FC)/aug-cc-pVTZ//MP2(FC)/aug-cc-pVTZ computational level; the bonding in the reactants and products for these transfer reactions are well-matched and thermochemical calculations at this level are expected to be very accurate, providing checks on the G3 HOF calculations.
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Affiliation(s)
- Niny Z. Rao
- Department of Chemistry and Biochemistry, College of Science, Health and the Liberal Arts, Philadelphia University, 4201 Henry Avenue, Philadelphia, PA 19144
| | | | - Charles W. Bock
- Department of Chemistry and Biochemistry, College of Science, Health and the Liberal Arts, Philadelphia University, 4201 Henry Avenue, Philadelphia, PA 19144
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Rao NZ, Larkin JD, Bock CW. A Comparison of the Structure and Bonding in the Aliphatic Boronic R-B(OH) 2 and Borinic R-BH(OH) acids (R=H; NH 2, OH, and F): A Computational Investigation. Struct Chem 2016; 27:1081-1091. [PMID: 29805241 PMCID: PMC5967406 DOI: 10.1007/s11224-015-0730-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 12/15/2015] [Indexed: 10/22/2022]
Abstract
Boronic acids, R-B(OH)2, play an important role in synthetic, biological, medicinal, and materials chemistry. This investigation compares the structure and bonding surrounding the boron atoms in the simple aliphatic boronic acids, R-B(OH)2 (R = H; NH2, OH, and F) and the analogous borinic acids, R-BH(OH). Geometry optimizations were performed using second-order Møller-Plesset perturbation theory (MP2) with the Dunning-Woon aug-cc-pVTZ, aug-cc-pVQZ and aug-cc-pV5Z basis sets; single-point CCSD(FC)/aug-cc-pVTZ//MP2(FC)/aug-cc-pVTZ level calculations were used to generate a QCI density for Natural Bond Orbital analyses of the bonding. The optimized boron-oxygen bond lengths for the X-B-Ot-H trans-branch of the endo-exo form of the boronic acids and for the X-B-O-H cis-branch of the boronic and borinic acids (X = N, O, and F respectively) decrease as the electronegativity of X increases. The boron-oxygen bond lengths are generally longer in the endo-exo or anti forms of the boronic acids than in the corresponding borinic acids. NBO analyses suggest the boron-oxygen bond in H2BOH is a double bond; the boron-oxygen bonding in the remaining boronic and borinic acids in this study have a significant contribution from dative pπ-pπ bonding. Values for [Formula: see text] for the highly balanced reaction, R-B(OH)2 + R-BH2 → 2 R-BH(OH), suggest that the bonding surrounding the boron atom is stronger in the borinic acid than in the corresponding boronic acid.
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Affiliation(s)
- Niny Z. Rao
- Department of Chemistry and Biochemistry, College of Science, Health and the Liberal Arts, Philadelphia University, 4201 Henry Avenue, Philadelphia, PA 19144
| | | | - Charles W. Bock
- Department of Chemistry and Biochemistry, College of Science, Health and the Liberal Arts, Philadelphia University, 4201 Henry Avenue, Philadelphia, PA 19144
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Bock CW, Larkin JD. Heats of Formation for the Boronic Acids R-B(OH) 2 and Boroxines R 3B 3O 3 (R=H, Li, HBe, H 2B, H 3C, H 2N, HO, F, and Cl) Calculated at the G2, G3, and G4 Levels of Theory. COMPUT THEOR CHEM 2012; 986:35-42. [PMID: 24653975 DOI: 10.1016/j.comptc.2012.02.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Boronic acids (R-B(OH)2) and their boroxine (R3B3O3) dehydration products have emerged as important classes of compounds with a multitude of diverse applications. However, the available heats of formation for these compounds are not always as accurate as would be required for further use. In this study the heats of formation at 298.15 K of R-B(OH)2 and R3B3O3 (R = H, Li, HBe, H2B, H3C, H2N, HO, F, and Cl) have been calculated at the G2, G3[G3B3], and G4 levels of theory and used to determine the enthalpy changes for the dehydration reactions: 3 R-B(OH)2 → R3B3O3 + 3 H2O; comparisons are made with other rigorous levels of theory, e.g. CBS-Q[CBS-QB3] and W1U, as well as with experimental values wherever possible. Enthalpy changes for the dehydration reactions have also been calculated using second-order Møller-Plesset perturbation theory (MP2) with the Dunning-Woon correlation-consistent aug-cc-pVDZ and aug-cc-pVTZ basis sets, and B3LYP density functional theory with the 6-311++G(2df,2pd) basis set. With the exception of H2N-B(OH)2, the dehydration reactions are consistently predicted to be exothermic. Our results provide a cautionary note for the use of the B3LYP functional in the calculation of structures and energies of boronic acids and boroxines. Where comparisons could be made, the G4 and W1U predictions for the heats of formation of these boron compounds differ significantly.
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Affiliation(s)
- Charles W Bock
- Department of Chemistry and Biochemistry, School of Science and Health, Philadelphia University, School House Lane and Henry Avenue, Philadelphia, PA 19144
| | - Joseph D Larkin
- The National Institutes of Health, National Heart, Lung and Blood Institute, Bldg. 50, Bethesda, MD 20851
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Bhat KL, Markham GD, Larkin JD, Bock CW. Thermodynamics of boroxine formation from the aliphatic boronic acid monomers R-B(OH)2 (R = H, H3C, H2N, HO, and F): a computational investigation. J Phys Chem A 2011; 115:7785-93. [PMID: 21650154 PMCID: PMC3154741 DOI: 10.1021/jp202409m] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Boroxines are the six-membered cyclotrimeric dehydration products of organoboronic acids, 3R–B(OH)2 → R3B3O3 + 3H2O, and in recent years have emerged as a useful class of organoboron molecules with applications in organic synthesis both as reagents and catalysts, as structural components in boronic-acid-derived pharmaceutical agents, and as anion acceptors and electrolyte additives for battery materials [Korich, A. L.; Iovine, P. M. Dalton Trans. 2010, 39, 1423−1431]. Second-order Møller–Plesset perturbation theory, in conjunction with the Dunning–Woon correlation-consistent cc-pVDZ, aug-cc-pVDZ, cc-pVTZ, and aug-cc-pVTZ basis sets, was used to investigate the structures and relative energies of the endo–exo, anti, and syn conformers of the aliphatic boronic acids R–B(OH)2 (R = H, H3C, H2N, HO, and F), as well as the thermodynamics of their boroxine formation; single-point calculations at the MP2/aug-cc-pVQZ, MP2/aug-cc-pV5Z, and CCSD(T)/aug-cc-pVTZ levels using the MP2/aug-cc-pVTZ optimized geometries were also performed in selected cases. The endo–exo conformer was generally lowest in energy in vacuo, as well as in PCM and CPCM models of aqueous and carbon tetrachloride media. The values of ΔH(298)(0) for boroxine formation via dehydration from the endo–exo conformers of these aliphatic boronic acids ranged from −2.9 for (H2N)3B3O3 to +12.2 kcal/mol for H3B3O3 at the MP2/aug-cc-pVTZ level in vacuo; for H3B3O3, the corresponding values in PCM/UFF implicit carbon tetrachloride and aqueous media were +11.2 and +9.8 kcal/mol, respectively. On the basis of our calculations, we recommend that ΔHf(298K) for boroxine listed in the JANAF compilation needs to be revised from −290.0 to approximately −277.0 kcal/mol.
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Affiliation(s)
- Krishna L. Bhat
- Department of Chemistry, Widener University, Chester, PA 19013
| | - George D. Markham
- The Institute for Cancer Research, Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, PA 19111
| | - Joseph D. Larkin
- The National Institutes of Health, National Heart, Lung and Blood Institute, Bldg. 50, Bethesda, MD 20851
| | - Charles W. Bock
- Department of Chemistry and Biochemistry, School of Science and Health, Philadelphia University, School House Lane and Henry Avenue, Philadelphia, PA 19144
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Larkin JD, Fossey JS, James TD, Brooks BR, Bock CW. A computational investigation of the nitrogen-boron interaction in o-(N,N-dialkylaminomethyl)arylboronate systems. J Phys Chem A 2010; 114:12531-9. [PMID: 21050022 DOI: 10.1021/jp1087674] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
o-(N,N-Dialkylaminomethyl)arylboronate systems are an important class of compounds in diol-sensor development. We report results from a computational investigation of fourteen o-(N,N-dialkylaminomethyl)arylboronates using second-order Møller-Plesset (MP2) perturbation theory. Geometry optimizations were performed at the MP2/cc-pVDZ level and followed by single-point calculations at the MP2/aug-cc-pVDZ(cc-pVTZ) levels. These results are compared to those from density functional theory (DFT) at the PBE1PBE(PBE1PBE-D)/6-311++G(d,p)(aug-cc-pVDZ) levels, as well as to experiment. Results from continuum PCM and CPCM solvation models were employed to assess the effects of a bulk aqueous environment. Although the behavior of o-(N,N-dialkylaminomethyl) free acid and ester proved to be complicated, we were able to extract some important trends from our calculations: (1) for the free acids the intramolecular hydrogen-bonded B-O-H···N seven-membered ring conformers 12 and 16 are found to be slightly lower in energy than the dative-bonded N→B five-membered ring conformers 10 and 14 while conformers 13 and 17, with no direct boron-nitrogen interaction, are significantly higher in energy than 12 and 16; (2) for the esters where no intramolecular B-O-H···N bonded form is possible, the N→B conformers 18 and 21 are significantly lower in energy than the no-interaction forms 20 and 23; (3) H(2)O insertion reactions into the N→B structures 10, 14, 18, and 21 leading to the seven-membered intermolecular hydrogen-bonded B···OH(2)···N ring structures 11, 15, 19, and 22 are all energetically favorable.
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Affiliation(s)
- Joseph D Larkin
- National Heart, Lung, and Blood Institute, The National Institutes of Health, Building 50, Bethesda, Maryland 20851, USA
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Larkin JD, Markham GD, Milkevitch M, Brooks BR, Bock CW. Computational investigation of the oxidative deboronation of boroglycine, H2N-CH2-B(OH)2, Using H2O and H2O2. J Phys Chem A 2010; 113:11028-34. [PMID: 19810757 DOI: 10.1021/jp904149w] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report results from a computational investigation of the oxidative deboronation of boroglycine, H2N-CH2-B(OH)2, using H2O and H2O2 as the reactive oxygen species (ROS) to yield aminomethanol, H2N-CH2-OH; these results complement our study on the protodeboronation of boroglycine to produce methylamine, H2N-CH3 (Larkin et al. J. Phys. Chem. A 2007, 111, 6489-6500). Second-order Møller-Plesset (MP2) perturbation theory with Dunning-Woon correlation-consistent (cc) basis sets were used for the calculations with comparisons made to results from density functional theory (DFT) at the PBE1PBE/6-311++G(d,p)(cc-pVDZ) levels. The effects of a bulk aqueous environment were also incorporated into the calculations employing PCM and CPCM methodology. Using H2O as the ROS, the reaction H2O + H2N-CH2-B(OH)2 --> H2N-CH2-OH + H-B(OH)2 was calculated to be endothermic; the value of DeltaH(298)(0) was +12.0 kcal/mol at the MP2(FC)/cc-pVTZ computational level in vacuo and +13.7 kcal/mol in PCM aqueous media; the corresponding value for the activation barrier, DeltaH(double dagger), was +94.3 kcal/mol relative to the separated reactants in vacuo and +89.9 kcal/mol in PCM aqueous media. In contrast, the reaction H2O2 + H2N-CH2-B(OH)2 --> H2N-CH2-OH + B(OH)3 was calculated to be highly exothermic with an DeltaH(298)(0) value of -100.9 kcal/mol at the MP2(FC)/cc-pVTZ computational level in vacuo and -99.6 kcal/mol in CPCM aqueous media; the highest-energy transition state for the multistep process associated with this reaction involved the rearrangement of H2N-CH2-B(OH)(OOH) to H2N-CH2-O-B(OH)2 with a DeltaH(double dagger) value of +23.2 kcal/mol in vacuo relative to the separated reactants. These computational results for boroglycine are in accord with the experimental observations for the deboronation of the FDA approved anticancer drug bortezomib (Velcade, PS-341), where it was found to be the principle deactivation pathway (Labutti et al. Chem. Res. Toxicol. 2006, 19, 539-546).
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Affiliation(s)
- Joseph D Larkin
- The National Institutes of Health, National Heart, Lung, and Blood Institute, 5635 Fishers Lane, Rockville, Maryland 20852, USA
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Taylor JC, Bock CW, Takusagawa F, Markham GD. Discovery of novel types of inhibitors of S-adenosylmethionine synthesis by virtual screening. J Med Chem 2009; 52:5967-73. [PMID: 19739644 DOI: 10.1021/jm9006142] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
S-adenosylmethionine (AdoMet) lies at an intersection of nucleotide and amino acid metabolism and performs a multitude of metabolic functions. AdoMet formation is catalyzed by S-adenosylmethionine synthetase (ATP: L-methionine S-adenosyltransferase (MAT)), which is a target for development of anticancer and antimicrobial agents. High affinity MAT inhibitors have been found through computational docking of more than 200000 compounds for predicted binding to the crystallographically defined nucleotide binding region of the enzyme's active site. Two of the top scoring candidate compounds had IC(50) values less than 10 nM, more than 10000-fold lower than the substrates' K(M) values. The compounds are structurally unrelated to the natural ligands of the enzyme. The enzyme is protected from inhibition by ATP, but not by methionine, consistent with binding at the adenosyl region of the active site. These results validate in silico screening as a robust approach to the discovery of inhibitors of this chemotherapeutically relevant enzyme.
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Affiliation(s)
- John C Taylor
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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Markham GD, Takusagawa F, Dijulio AM, Bock CW. An investigation of the catalytic mechanism of S-adenosylmethionine synthetase by QM/MM calculations. Arch Biochem Biophys 2009; 492:82-92. [PMID: 19699176 DOI: 10.1016/j.abb.2009.08.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Accepted: 08/14/2009] [Indexed: 12/12/2022]
Abstract
Catalysis by S-adenosylmethionine synthetase has been investigated by quantum mechanical/molecular mechanical calculations, exploiting structures of the active crystalline enzyme. The transition state energy of +19.1 kcal/mol computed for a nucleophilic attack of the methionyl sulfur on carbon-5' of the nucleotide was indistinguishable from the experimental (solution) value when the QM residues were an uncharged histidine that hydrogen bonds to the leaving oxygen-5' and an aspartate that chelates a Mg2+ ion, and was similar (+18.8 kcal/mol) when the QM region also included the active site arginine and lysines. The computed energy difference between reactant and product was also consistent with their equimolar abundance in co-crystals. The calculated geometrical changes support catalysis of a S(N)2 reaction through hydrogen bonding of the liberated oxygen-5' to the histidine, charge neutralization by the two Mg2+ ions, and stabilization of the product sulfonium cation through a close, non-bonded, contact between the sulfur and the ribose oxygen-4'.
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Affiliation(s)
- George D Markham
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA.
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Larkin JD, Bhat KL, Markham GD, James TD, Brooks BR, Bock CW. A computational characterization of boron-oxygen multiple bonding in HN=CH-CH=CH-NH-BO. J Phys Chem A 2008; 112:8446-54. [PMID: 18707068 DOI: 10.1021/jp800125p] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Structures, relative energies, and bonding characteristics for various conformers of 3-imino-N-(oxoboryl)prop-1-en-1-amine, HN=CH-CH=CH-NH-BO, and the corresponding borocycle (-HN=CH-CH=CH-NH-B-)O are discussed using results from second-order Møller-Plesset (MP2) perturbation theory with the Dunning-Woon correlation-consistent cc-pVDZ, aug-cc-pVDZ, and cc-pVTZ basis sets. These MP2 results are compared to those from computationally efficient density functional theory (DFT) calculations using the LDA, PBE, TPSS, BLYP, B3LYP, BVP86, OLYP, O3LYP, and PBE1PBE functionals in conjunction with the economical Pople-type 6-311++G(d,p) basis set to evaluate the suitability of these DFT/6-311++G(d,p) levels for use with larger boron-containing systems. The effects of an aqueous environment were incorporated into the calculations using COSMO methodology. The calculated boron-oxygen bond lengths, orbital compositions, and bond orders in all the (acyclic) HN=CH-CH=CH-NH-BO conformers were consistent with the presence of a boron-oxygen triple bond, similar to that found in H-BO and H2N-BO. The (-HN=CH-CH=CH-NH-B-)O borocycle is predicted to be planar (C2v symmetry), and it is approximately 30 kcal/mol lower in energy than any of the (acyclic) HN=CH-CH=CH-NH-BO conformers; the boron-oxygen bond in this borocycle has significant double bond character, a bonding scheme for which there has been only one experimental structure reported in the literature (Vidovic, D. ; et al. J. Am. Chem. Soc. 2005, 127, 4566- 4569).
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Affiliation(s)
- Joseph D Larkin
- Department of Chemistry, Bloomsburg University of Pennsylvania, Bloomsburg, Pennsylvania 17815, USA.
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Panchenko YN, Bock CW, Larkin JD, Abramenkov AV, Kühnemann F. Predictive abilities of scaled quantum-mechanical molecular force fields: application to 2-methylbuta-1,3-diene (isoprene). Struct Chem 2008. [DOI: 10.1007/s11224-008-9297-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Larkin JD, Milkevitch M, Bhat KL, Markham GD, Brooks BR, Bock CW. Dimers of boroglycine and methylamine boronic acid: a computational comparison of the relative importance of dative versus hydrogen bonding. J Phys Chem A 2007; 112:125-33. [PMID: 18072757 DOI: 10.1021/jp076537h] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Boronic acids are widely used in materials science, pharmacology, and the synthesis of biologically active compounds. In this Article, geometrical structures and relative energies of dimers of boroglycine, H2N-CH2-B(OH)2, and its constitutional isomer H3C-NH-B(OH)2, were computed using second-order Møller-Plesset perturbation theory and density functional theory; Dunning-Woon correlation-consistent cc-pVDZ, aug-cc-pVDZ, cc-pVTZ, and aug-cc-pVTZ basis sets were employed for the MP2 calculations, and the Pople 6-311++G(d,p) basis set was employed for a majority of the DFT calculations. Effects of an aqueous environment were incorporated into the results using PCM and COSMO-RS methodology. The lowest-energy conformer of the H2N-CH2-B(OH)2 dimer was a six-membered ring structure (chair conformation; Ci symmetry) with two intermolecular B:N dative-bonds; it was 14.0 kcal/mol lower in energy at the MP2/aug-cc-pVDZ computational level than a conformer with the classic eight-centered ring structure (Ci symmetry) in which the boroglycine monomers are linked by a pair of H-O...H bonds. Compared to the results of MP2 calculations with correlation-consistent basis sets, DFT calculations using the PBE1PBE and TPSS functionals with the 6-311++G(d,p) basis set were significantly better at predicting relative conformational energies of the H2N-CH2-B(OH)2 and H3C-NH-B(OH)2 dimers than corresponding calculations using the BLYP, B3LYP, OLYP, and O3LYP functionals, particularly with respect to dative-bonded structures.
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Affiliation(s)
- Joseph D Larkin
- Department of Chemistry, Bloomsburg University of Pennsylvania, Bloomsburg, Pennsylvania 17815, USA. jlarkin@ bloomu.edu
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Larkin JD, Bhat KL, Markham GD, Brooks BR, Lai JH, Bock CW. A computational investigation of the geometrical structure and protodeboronation of boroglycine, H2N-CH2-B(OH)2. J Phys Chem A 2007; 111:6489-500. [PMID: 17595064 DOI: 10.1021/jp0700682] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this article the geometrical structure of the simple, achiral, alpha-amino boronic acid boroglycine, H2N-CH2-B(OH)2, was investigated using density functional theory (DFT), second-order Møller-Plesset (MP2) perturbation theory, and coupled cluster methodology with single- and double-excitations (CCSD); the effects of an aqueous environment were incorporated into the results by using a few explicit water molecules and/or self-consistent reaction field (SCRF) calculations with the IEF polarizable continuum model (PCM). Neutral reaction mechanisms were investigated for the direct protodeboronation (hydrolysis) of boroglycine (H2O+H2N-CH2-B(OH)2-->B(OH)3+H2N-CH3), for which DeltaH degrees 298 was -21.9 kcal/mol at the MP2(FC)/aug-cc-pVDZ level, and for the 1,2-carbon-to-nitrogen shift of the -B(OH)2 moiety (H2N-CH2-B(OH)2-->H3C-NH-B(OH)2), for which the corresponding value of DeltaH degrees 298 was -18.2 kcal/mol. A boron-oxygen double-bonded intermediate was found to play an important role in the 1,2-rearrangement mechanism.
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Affiliation(s)
- Joseph D Larkin
- Department of Chemistry, Bloomsburg University of Pennsylvania, Bloomsburg, Pennsylvania 17815, USA.
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Larkin JD, Bhat KL, Markham GD, Brooks BR, Schaefer HF, Bock CW. Structure of the Boronic Acid Dimer and the Relative Stabilities of Its Conformers. J Phys Chem A 2006; 110:10633-42. [PMID: 16956246 DOI: 10.1021/jp062407h] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Despite the widespread use of boronic acids in materials science and as pharmaceutical agents, many aspects of their structure and reactivity are not well understood. In this research the boronic acid dimer, [HB(OH)(2)](2), was studied by second-order Møller-Plesset (MP2) perturbation theory and coupled cluster methodology with single and double excitations (CCSD). Pople split-valence 6-31+G*, 6-311G**, and 6-311++G** and Dunning-Woon correlation-consistent cc-pVDZ, aug-cc-pVDZ, cc-pVTZ, and aug-cc-pVTZ basis sets were employed for the calculations. A doubly hydrogen-bonded conformer (1) of the dimer was consistently found to be lowest in energy; the structure of 1 was planar (C(2h)) at most computational levels employed but was significantly nonplanar (C(2)) at the MP2/6-311++G** and CCSD/6-311++G** levels, the result of an intrinsic problem with Pople-type sp-diffuse basis functions on heavy atoms. The dimerization energy, enthalpy, and free energy for the formation of (1) from the exo-endo conformer of the monomer were -10.8, -9.2, and +1.2 kcal/mol, respectively, at the MP2/aug-cc-pVTZ level. Several other hydrogen-bonded conformers of the dimer were local minima on the potential energy surface (PES) and ranged from 2 to 5 kcal/mol higher in energy than 1. Nine doubly OH-bridged conformers, in which the boron atoms were tetracoordinated, were also local minima on the PES, but they were all greater than 13 kcal/mol higher in energy than 1; doubly H-bridged structures proved to be transition states. MP2 and CCSD results were compared to those from the BLYP, B3LYP, OLYP, O3LYP, PBE1PBE, and TPSS functionals with the 6-311++G** and aug-cc-pVTZ basis sets; the PBE1PBE functional performed best relative to the MP2 and CCSD results. Self-consistent reaction field (SCRF) calculations predict that boronic acid dimerization is less favorable in solution than in vacuo.
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Affiliation(s)
- Joseph D Larkin
- Center for Computational Chemistry, University of Georgia, Athens, GA 30602, USA.
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Bhat KL, Lai JH, Markham GD, DiJulio AM, Bock CW. Amine-Catalyzed B−O−C Bond Formation: Mechanistic Insights from Density Functional Theory and Second-Order Møller−Plesset Perturbation Theory. Organometallics 2006. [DOI: 10.1021/om0509239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Krishna L. Bhat
- Department of Chemistry and Biochemistry, School of Science and Health, Philadelphia University, School House Lane and Henry Avenue, Philadelphia, Pennsylvania 19144, Department of Biochemistry, Tufts University School of Medicine, 136 Harrison Avenue, Boston, Massachusetts 02111, The Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, Pennsylvania 19111, and Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, Pennsylvania 18104
| | - Jack H. Lai
- Department of Chemistry and Biochemistry, School of Science and Health, Philadelphia University, School House Lane and Henry Avenue, Philadelphia, Pennsylvania 19144, Department of Biochemistry, Tufts University School of Medicine, 136 Harrison Avenue, Boston, Massachusetts 02111, The Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, Pennsylvania 19111, and Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, Pennsylvania 18104
| | - George D. Markham
- Department of Chemistry and Biochemistry, School of Science and Health, Philadelphia University, School House Lane and Henry Avenue, Philadelphia, Pennsylvania 19144, Department of Biochemistry, Tufts University School of Medicine, 136 Harrison Avenue, Boston, Massachusetts 02111, The Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, Pennsylvania 19111, and Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, Pennsylvania 18104
| | - Anthony M. DiJulio
- Department of Chemistry and Biochemistry, School of Science and Health, Philadelphia University, School House Lane and Henry Avenue, Philadelphia, Pennsylvania 19144, Department of Biochemistry, Tufts University School of Medicine, 136 Harrison Avenue, Boston, Massachusetts 02111, The Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, Pennsylvania 19111, and Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, Pennsylvania 18104
| | - Charles W. Bock
- Department of Chemistry and Biochemistry, School of Science and Health, Philadelphia University, School House Lane and Henry Avenue, Philadelphia, Pennsylvania 19144, Department of Biochemistry, Tufts University School of Medicine, 136 Harrison Avenue, Boston, Massachusetts 02111, The Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, Pennsylvania 19111, and Department of Chemistry, Muhlenberg College, 2400 Chew Street, Allentown, Pennsylvania 18104
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Bock CW, Markham GD, Katz AK, Glusker JP. The Arrangement of First- and Second-shell Water Molecules Around Metal Ions: Effects of Charge and Size. Theor Chem Acc 2006. [DOI: 10.1007/s00214-005-0056-2] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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21
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Lai JH, Liu Y, Wu W, Zhou Y, Maw HH, Bachovchin WW, Bhat KL, Bock CW. Synthesis and Structural Investigation of Internally Coordinated α-Amidoboronic Acids. J Org Chem 2005; 71:512-9. [PMID: 16408958 DOI: 10.1021/jo051757h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
[structure: see text] Six new N-acyl-boroGly derivatives, along with their N-acyl-boroSar analogues, have been synthesized by modification of conventional procedures. Structural characterization of these alpha-amidoboronic acids was accomplished by extensive use of 11B and 1H NMR spectroscopy. These compounds were prepared to determine the extent of intramolecular B-O dative bond formation within the context of a five-membered (:O=C-N-C-B) ring motif. It is shown that the formation of such dative bonds depends on the nature of the substituents at both the acyl carbon and the nitrogen atoms. Computational evidence from second-order Møller-Plesset perturbation theory is provided in support of these findings.
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Affiliation(s)
- Jack H Lai
- Department of Biochemistry, Tufts University School of Medicine, 136 Harrison Avenue, Boston, Massachusetts 02111, USA
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22
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Larkin JD, Bock CW, Schaefer Iii HF. Assessing Alkyl-, Silyl-, and Halo-Substituent Effects on the Electron Affinities of Silyl Radicals. J Phys Chem A 2005; 109:10100-5. [PMID: 16838930 DOI: 10.1021/jp052439p] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Neutral anion energy differences for a large class of alpha-substituted silyl radicals have been computed to determine the effect of alkyl, silyl, and halo substituents on their electron affinities. In particular, we report theoretical predictions of the adiabatic electron affinities (AEAs), vertical electron affinities (VEAs), and vertical detachment energies (VDEs) for a series of methyl-, silyl-, and halo-substituted silyl radical compounds. This work utilizes the carefully calibrated DZP++ basis set, in conjunction with the pure BLYP and OLYP functionals, as well as with the hybrid B3LYP, BHLYP, PBE1PBE, MPW1K, and O3LYP functionals. Bromine has the largest effect in stabilizing the anions, and the BLYP/DZP++ AEA for SiBr(3) is 3.29 eV. The other predicted electron affinities are for SiH(3) (1.37 eV), SiH(2)CH(3) (1.09 eV), SiH(2)F (1.54 eV), SiH(2)Cl (1.94 eV), SiH(2)Br (2.05 eV), SiH(2)(SiH(3)) (1.77 eV), SiH(CH(3))(2) (0.92 eV), SiHF(2) (1.86 eV), SiHCl(2) (2.53 eV), SiHBr(2) (2.67 eV), Si(CH(3))(3) (0.86 eV), SiF(3) (2.66 eV), SiCl(3) (3.21 eV), Si(SiH(3))(3) (2.25 eV), and SiFClBr (3.13 eV). For the five silyl radicals where experimental data are available, the BLYP functional gives the most accurate determination of AEAs; the average absolute error is 0.04(1) eV, whereas the corresponding errors for the O3LYP, MPW1K, PBE1PBE, B3LYP, OLYP, and BHLYP functionals are 0.05(8), 0.06(0), 0.06(3), 0.08(5), 0.11(5), and 0.15(3) eV, respectively.
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Affiliation(s)
- Joseph D Larkin
- Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, USA
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23
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Bhat KL, Howard NJ, Rostami H, Lai JH, Bock CW. Intramolecular dative bonds involving boron with oxygen and nitrogen in boronic acids and esters: a computational study. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.theochem.2005.01.033] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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24
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Bock CW, Trachtman M, George P. The effect of including polarization functions on the geometrical parameters calculated for pyridine. J Comput Chem 2004; 7:153-157. [DOI: 10.1002/jcc.540070208] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/1985] [Accepted: 10/29/1985] [Indexed: 11/10/2022]
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Hayik S, Bhat KL, Bock CW. Structure of 4-[4-(Dimethylamino)-Phenylazo] Benzeneboronic Acid and Its Cyclic Esters with D-Glucose: A Computational Study. Struct Chem 2004. [DOI: 10.1023/b:stuc.0000011248.28922.3b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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26
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Sim E, Larkin J, Burke K, Bock CW. Testing the kinetic energy functional: Kinetic energy density as a density functional. J Chem Phys 2003. [DOI: 10.1063/1.1565316] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Bock CW, Markham GD, Katz AK, Glusker JP. The arrangement of first- and second-shell water molecules in trivalent aluminum complexes: results from density functional theory and structural crystallography. Inorg Chem 2003; 42:1538-48. [PMID: 12611521 DOI: 10.1021/ic020602e] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structural and energetic features of a variety of gas-phase aluminum ion hydrates containing up to 18 water molecules have been studied computationally using density functional theory. Comparisons are made with experimental data from neutron diffraction studies of aluminum-containing crystal structures listed in the Cambridge Structural Database. Computational studies indicate that the hexahydrated structure Al[H(2)O](6)(3+) (with symmetry T(h)()), in which all six water molecules are located in the innermost coordination shell, is lower in energy than that of Al[H(2)O](5)(3+).[H(2)O], where only five water molecules are in the inner shell and one water molecule is in the second shell. The analogous complex with four water molecules in the inner shell and two in the outer shell undergoes spontaneous proton transfer during the optimization to give [Al[H(2)O](2)[OH](2)](+).[H(3)O(+)](2), which is lower in energy than Al[H(2)O](6)(3+); this finding of H(3)O(+) is consistent with the acidity of concentrated Al(3+) solutions. Since, however, Al[H(2)O](6)(3+) is detected in solutions of Al(3+), additional water molecules are presumed to stabilize the hexa-aquo Al(3+) cation. Three models of a trivalent aluminum ion complex surrounded by a total of 18 water molecules arranged in a first shell containing 6 water molecules and a second shell of 12 water molecules are discussed. We find that a model with S(6) symmetry for which the Al[H(2)O](6)(3+) unit remains essentially octahedral and participates in an integrated hydrogen bonded network with the 12 outer-shell water molecules is lowest in energy. Interactions between the 12 second-shell water molecules and the trivalent aluminum ion in Al[H(2)O](6)(3+) do not appear to be sufficiently strong to orient the dipole moments of these second-shell water molecules toward the Al(3+) ion.
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Affiliation(s)
- Charles W Bock
- Philadelphia University, Henry Avenue and Schoolhouse Lane, Pennsylvania 19144, USA
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28
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Bock CW, Brendley WH, Hamann H, Bhat KL. Formation of bis (chloromethyl) ether in the vapor phase: a computational investigation. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s0166-1280(02)00577-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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30
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Bock CW, Trachtman M. Binding of the two-valence-electron metal ions Sc(+), Ti(2+), and V(3+) to the second-row hydrides BeH(2), BH(3), NH(3), OH(2), and FH: a computational study. Inorg Chem 2002; 41:4680-8. [PMID: 12206691 DOI: 10.1021/ic020216x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report results from a computational study of the binding in complexes formed from one of the transition-metal ions Sc(+), Ti(2+), or V(3+), each of which has two valence electrons outside an argon core, and one of the second-row hydrides FH, OH(2), NH(3), BH(3), or BeH(2). The complexes that involve the electron-rich ligands FH, OH(2), and NH(3) have strong ion-dipole components to their binding. There are large stabilization energies for sigma-interactions that transfer charge from occupied lone-pair natural bond orbitals on the F, O, or N atom of the (idealized) Lewis structure into empty non-Lewis orbitals on the metal ions; these interactions effectively increase electron density in the bonding region between the metal ion and liganded atom, and the metal ions in these complexes act in the capacity of Lewis acids. The complexes formed from the electron-poor hydrides BH(3) and BeH(2) consistently incorporate bridging hydrogen atoms to support binding, and there are large stabilization energies for interactions that transfer charge from the Be-H or B-H bonds into the region between the metal ion and liganded atom. The metal ions in Sc(+)-BeH(2), Ti(2+)-BeH(2), Ti(2+)-BH(3), and V(3+)-BH(3) act in the capacity of Lewis acids, whereas the scandium ion in Sc(+)-BH(3) acts as a Lewis base.
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Affiliation(s)
- Charles W Bock
- Department of Chemistry and Biochemistry, School of Science and Health, Philadelphia University, Philadelphia, PA 19144, USA.
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31
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Markham GD, Norrby PO, Bock CW. S-adenosylmethionine conformations in solution and in protein complexes: conformational influences of the sulfonium group. Biochemistry 2002; 41:7636-46. [PMID: 12056895 DOI: 10.1021/bi025682c] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
S-Adenosylmethionine (AdoMet) and other sulfonium ions play central roles in the metabolism of all organisms. The conformational preferences of AdoMet and two other biologically important sulfonium ions, S-methylmethionine and dimethylsulfonioproprionic acid, have been investigated by NMR and computational studies. Molecular mechanics parameters for the sulfonium center have been developed for the AMBER force field to permit analysis of NMR results and to enable comparison of the relative energies of the different conformations of AdoMet that have been found in crystal structures of complexes with proteins. S-Methylmethionine and S-dimethylsulfonioproprionate adopt a variety of conformations in aqueous solution; a conformation with an electrostatic interaction between the sulfonium sulfur and the carboxylate group is not noticeably favored, in contrast to the preferred conformation found by in vacuo calculations. Nuclear Overhauser effect measurements and computational results for AdoMet indicate a predominantly anti conformation about the glycosidic bond with a variety of conformations about the methionyl C(alpha)-C(beta) and C(beta)-C(gamma) bonds. An AdoMet conformation in which the positively charged sulfonium sulfur is near an electronegative oxygen in the ribose ring is common. Comparisons of NMR results for AdoMet with those for the uncharged S-adenosylhomocysteine and 5'-methylthioadenosine, and the anionic ATP, indicate that the solution conformations are not dictated mainly by molecular charge. In 20 reported structures of AdoMet.protein complexes, both anti and syn glycosidic torsional angles are found. The methionyl group typically adopts an extended conformation in complexes with enzymes that transfer the methyl group from the sulfonium center, but is more folded in complexes with proteins that do not catalyze reactions involving the sulfur and which can use the sulfonium sulfur solely as a binding site. The conformational energies of AdoMet in these crystal structures are comparable to those found for AdoMet in solution. The sulfonium sulfur is in van der Waals contact with a protein heteroatom in the structures of four proteins, which reflects an energetically favorable contact. Interactions of the sulfonium with aromatic rings are rarely observed.
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Affiliation(s)
- George D Markham
- The Institute for Cancer Research, Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, Pennsylvania 19111, USA.
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32
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Bock CW, Trachtman M, Murphy C, Muschert B, Mains GJ. Ab initio molecular orbital study of boron, aluminum, gallium .mu.-hydrido-bridged hexahydrides. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100159a041] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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33
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Cremer D, Kraka E, Gauss J, Bock CW. Theoretical determination of molecular structure and conformation. 19. Configurational changes of bridged annulenes: inversion at an ether oxygen atom. J Am Chem Soc 2002. [DOI: 10.1021/ja00276a014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Dobbs KD, Trachtman M, Bock CW, Cowley AH. Gallane-arsine, H3Ga.cntdot.AsH3: prediction of a stable Ga-As bonded species. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100376a006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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35
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George P, Glusker JP, Bock CW. Ab initio study of protonated radical species that may be involved in the enzyme-coenzyme B12 catalyzed dehydration of 1,2-dihydroxyethane. J Am Chem Soc 2002. [DOI: 10.1021/ja00145a032] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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36
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George P, Bock CW, Glusker JP. Semiempirical and ab initio molecular orbital studies on the mechanism of the acid-catalyzed isomerization benzene oxide .fwdarw. phenol. 1. Structure of protonated benzene oxide. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100384a034] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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37
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George P, Bock CW, Trachtman M. An ab initio study of the planar hydrogen maleate ion with full geometry optimization. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100234a002] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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38
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Markham GD, Bock CW. Interaction of the Sulfides CH3SCH3 and CH3SCH2CO2- with Water Molecules. An ab Initio Molecular Orbital Study. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100025a012] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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39
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Bock CW, Roberts C, O'Malley K, Trachtman M, Mains GJ. An ab initio molecular orbital study of the structures, stabilities, and spectra of tris[tetrahydroborato(1-)]boron, tris[tetrahydroborato(1-)]aluminum, and tris[tetrahydroaluminato(1-)]aluminum. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100191a026] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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40
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Bock CW, George P, Glusker JP. Ab initio molecular orbital studies on C2H5O+ and C2H4FO+: oxonium ion, carbocation, protonated aldehyde, and related transition-state structures. J Org Chem 2002. [DOI: 10.1021/jo00073a049] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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41
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Bock CW, Trachtman M. An ab initio molecular orbital study of the thermal decomposition mechanisms of ethylarsine and ethylgallane. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100199a040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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42
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Redington RL, Bock CW. MO study of singlets, triplets, and tunneling in tropolone. 1. Geometries, tunneling, and vibrations in the ground electronic state. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100178a011] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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43
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Cremer D, Schmidt T, Bock CW. Theoretical determination of molecular structure and conformation. 14. Is bicyclo[6.2.0]decapentaene aromatic or antiaromatic? J Org Chem 2002. [DOI: 10.1021/jo00215a018] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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De Mare GR, Panchenko YN, Bock CW. An MP2/6-31G*//MP2/6-31G* vibrational analysis of s-trans- and s-cis-acryloyl fluoride, CH2=CH-CF=O. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100056a008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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48
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Bock CW, George P, Trachtman M. Comparative molecular orbital study of the singlet state of o-benzyne and molecules with similar structural elements. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j150652a005] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Borisenko KB, Bock CW, Hargittai I. Intramolecular Hydrogen Bonding and Molecular Geometry of 2-Nitrophenol from a Joint Gas-Phase Electron Diffraction and ab Initio Molecular Orbital Investigation. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100056a012] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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50
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