Ab Initio Examination of Anomeric Effects in Tetrahydropyrans, 1,3-Dioxanes, and Glucose

Salzner, Ulrike; Schleyer, Paul v. R.

doi:10.1021/jo00087a035

Cited by 229 publications

(179 citation statements)

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“…These facts are congruent with our results of relative energy minima and with those previously described. 9,10 In a second contribution, Fuchs et al 20 studied 259 compounds containing the O-C-O moiety, which led them to conclude that conformers with an arrangement like eq-3 do not contribute to the rotational population, this time in agreement with our population results. Table 2 displays the energies of the hypothetical Lewis molecules.…”

supporting

confidence: 84%

“…All conformers are minima with no imaginary frequencies. It is worth noticing at this point that in Salzner and Schleyer's paper, 9 only four minima, conformers ax-1, ax-2, eq-2, and eq-3, of the six expected for the rotation of the methoxy group were described excluding from their calculations, at HF/6-31G(d) level, conformers ax-3 and eq-1. On the other hand, in the absence of symmetry in 1, and with evident computational limitations, Wiberg et al 10 considered that at HF/3-21G level it was acceptable to take into account only one minimum energy conformer for the axial configuration, ax-2, and two for the equatorial configuration, eq-2 and eq-3.…”

Section: A Energetic Considerationsmentioning

confidence: 97%

“…The term anomeric effect was introduced in 1958 by Lemieux 5 and refers to the tendency of an electronegative substituent at C 2 of a pyranoid ring (see Scheme 1) to adopt the axial rather than the equatorial orientation, in contrast with expectations based exclusively on steric [8][9][10] Recently, the study of the contributions of the electronic delocalization to the anomeric effect showed that the observed axial/equatorial conformational preference is not solely of stereoelectronic origin 11 since the stereoelectronic interactions present in the axial conformer are as important as the ones in the equatorial arrangement. The anomeric effect in 2-MeO-oxane was found to be 1.7 kcal/mol, from the difference of ∆G o for the axial/equatorial equilibrium of 1, 0.9 kcal/mol, and the A Value for the methoxy group, -0.8 kcal/mol (2, Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Toward the origin of the conformational preference of 2-methoxyoxane, a model useful to study the anomeric effect

Martínez¹,

Cortés²,

Leal³

et al. 2003

Arkivoc

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The potential energy curves resulting from the C 2 -O exo bond rotation of 2-OMeOxane were calculated. One minimum was found for the axial conformer at MP2/6-31G(d,p); B3LYP/6-31G(d,p); and HF/6-31G(d,p) levels, and two minima in the equatorial conformer. The difference in the entropy of mixing between both conformers has a positive value, close to zero, which means that the entropy is higher for the equatorial conformer. The Scheme of rotation of the methoxy group at position 2 of oxane with six conformers, usually employed to describe this conformational process, is inadequate.

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supporting

confidence: 84%

Section: A Energetic Considerationsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Toward the origin of the conformational preference of 2-methoxyoxane, a model useful to study the anomeric effect

Martínez¹,

Cortés²,

Leal³

et al. 2003

Arkivoc

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“…As one of the most important monosaccharides in nature, ␣-Dglucose plays vital roles in the life processes of both plants and animals. The gas-phase and solution-phase properties of ␣-D-glucose have been active areas for experimental [41][42][43] as well as theoretical studies [42][43][44][45][46][47][48][49][50] for many years. Unambiguous nomenclature has been developed to describe the various conformers of neutral and deprotonated ␣-D-glucose [45,50]; this nomenclature is elaborated upon in the Appendix of this report.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of the role of multiple hydrogen bonding in offering stability to negative ion adducts in electrospray mass spectrometry

Cai

Concha

Murray

et al. 2002

J. Am. Soc. Mass Spectrom.

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An experimental approach, electrospray mass spectrometry (ES-MS), and a theoretical approach employing computer modeling, have been used to characterize the interaction between small inorganic anions and neutral analyte molecules that form anionic adduct species in negative mode ES mass spectrometry. Certain anionic adducts of small saccharides (e.g., ␣-D-glucose, sucrose) have shown exceptional stability in ES mass spectra even when internal energies are raised at high "cone" voltages. Computer modeling studies reveal that multiple hydrogen bonding strengthens the interaction between these neutral molecules and the attaching anion. The equilibrium structures and stabilization energies of these anionic adducts have been evaluated by semi-empirical, ab initio, and density functional theory (DFT) methods. Chloride anion is found to be capable of forming "bridging" hydrogen bonds between monosaccharide rings of polysaccharides resulting in the stabilization of chloride adducts, thus reducing the tendency for the glycosidic bond to decompose. Moreover, the tendency for various hydroxyl hydrogens on saccharide molecules to dissociate in the form of HA ( [5][6][7][8], have been used to generate anionic adducts for ES-MS studies. The formation and decomposition of chloride adducts have been further investigated from a thermodynamic standpoint [9 -12]. However, the conditions that favor the formation and survival of anionic adducts have not been extensively defined and are not fully understood. Moreover, the interactions between neutral analyte molecules and the attaching small inorganic anions have not been fully characterized.Various mass spectrometry methods have been applied to probe the interactions between ions and neutral analyte molecules [13][14][15]. These methods typically evaluate enthalpies of ion-molecule reactions or unimolecular dissociations of ionic adducts to derive gasphase thermodynamic properties such as bond energies and ion affinities. In some cases, the nature of the ion-molecule interaction could be further elucidated by determining the difference in the entropy changes for competing decomposition pathways [16,17]. To date, the vast majority of ion-molecule interaction studies performed by mass spectrometry focus on positive ion studies of cationic adduct species, especially protonated molecules [14] and alkali metal adducts [18 -21]. Dication adduct species, such as alkaline earth metal [22] and transition metal [23] adducts of oligosaccharides have also been explored. Small inorganic anions attaching to neutral analyte molecules, on the other hand, have received far less research attention. However, a few studies employing anion attachment in negative ion ES-MS have appeared, such as reports on iodide attachment to acetone [24], chloride attachment to saccharides [1, 10 -12], and cyanide attachment (including covalent) to fullerenes [6,8]. In order to gain insight into the exact nature of the interactions between neutral analyte molecules and attaching small inorganic anions that are responsi...

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“…Thus, important features such as the oxygen lone pairs are captured, which are considered an important factor in determining energies of stable conformations of glucose. 32,45,46 The QM studies employ implicit solvent and include only the cation, as supported by the aforementioned experimental studies. The MD studies include the anion and cation as well as explicit water.…”

Section: ■ Introductionmentioning

confidence: 99%

Sodium Ion Interactions with Aqueous Glucose: Insights from Quantum Mechanics, Molecular Dynamics, and Experiment

Mayes

Tian

Nolte³

et al. 2013

J. Phys. Chem. B

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In the last several decades, significant efforts have been conducted to understand the fundamental reactivity of glucose derived from plant biomass in various chemical environments for conversion to renewable fuels and chemicals. For reactions of glucose in water, it is known that inorganic salts naturally present in biomass alter the product distribution in various deconstruction processes. However, the molecular-level interactions of alkali metal ions and glucose are unknown. These interactions are of physiological interest as well, for example, as they relate to cation-glucose cotransport. Here, we employ quantum mechanics (QM) to understand the interaction of a prevalent alkali metal, sodium, with glucose from a structural and thermodynamic perspective. The effect on B-glucose is subtle: a sodium ion perturbs bond lengths and atomic partial charges less than rotating a hydroxymethyl group. In contrast, the presence of a sodium ion significantly perturbs the partial charges of Î±-glucose anomeric and ring oxygens. Molecular dynamics (MD) simulations provide dynamic sampling in explicit water, and both the QM and the MD results show that sodium ions associate at many positions with respect to glucose with reasonably equivalent propensity. This promiscuous binding nature of Na + suggests that computational studies of glucose reactions in the presence of inorganic salts need to ensure thorough sampling of the cation positions, in addition to sampling glucose rotamers. The effect of NaCl on the relative populations of the anomers is experimentally quantified with light polarimetry. These results support the computational findings that Na + interacts similarly with a-and B-glucose. ABSTRACT: In the last several decades, significant efforts have been conducted to understand the fundamental reactivity of glucose derived from plant biomass in various chemical environments for conversion to renewable fuels and chemicals. For reactions of glucose in water, it is known that inorganic salts naturally present in biomass alter the product distribution in various deconstruction processes. However, the molecular-level interactions of alkali metal ions and glucose are unknown. These interactions are of physiological interest as well, for example, as they relate to cation-glucose cotransport. Here, we employ quantum mechanics (QM) to understand the interaction of a prevalent alkali metal, sodium, with glucose from a structural and thermodynamic perspective. The effect on β-glucose is subtle: a sodium ion perturbs bond lengths and atomic partial charges less than rotating a hydroxymethyl group. In contrast, the presence of a sodium ion significantly perturbs the partial charges of α-glucose anomeric and ring oxygens. Molecular dynamics (MD) simulations provide dynamic sampling in explicit water, and both the QM and the MD results show that sodium ions associate at many positions with respect to glucose with reasonably equivalent propensity. This promiscuous binding nature of Na + suggests that computational studies of g...

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Ab Initio Examination of Anomeric Effects in Tetrahydropyrans, 1,3-Dioxanes, and Glucose

Cited by 229 publications

References 1 publication

Toward the origin of the conformational preference of 2-methoxyoxane, a model useful to study the anomeric effect

Toward the origin of the conformational preference of 2-methoxyoxane, a model useful to study the anomeric effect

Evaluation of the role of multiple hydrogen bonding in offering stability to negative ion adducts in electrospray mass spectrometry

Sodium Ion Interactions with Aqueous Glucose: Insights from Quantum Mechanics, Molecular Dynamics, and Experiment

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