Mechanisms of glycopyranosyl and 5-thioglycopyranosyl transfer reactions in solution

Bennet, Andrew J.; Kitos, Theresa E.

doi:10.1039/b108446c

Cited by 32 publications

(34 citation statements)

References 107 publications

(139 reference statements)

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“…A notable efficiency of formation of an oxonium ion at m/z 331 is observed in the case of galactosides 3˛and 3 . The extent of consecutive fragmentation of these ions is relatively low as indicated by the high contribution of the oxonium ion to the total intensity of all fragment ions, that is, 66% and 65% in the case 3˛and 3ˇ, respectively.…”

Section: All Six Isomers Produce High Intensities Of [M C Nh 4 ]mentioning

confidence: 97%

Anomeric distinction and oxonium ion formation in acetylated glycosides

Denekamp

Sandlers

2005

J. Mass Spectrom.

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Collision-induced dissociation of ammonium-cationized alpha and beta acetyl pyranosidic isomers were studied and stereochemical dependence of the reactivity towards elimination of acetic acid from the anomeric position was found. It is shown that isomers that contain trans diacetyloxy groups at positions 1 and 2 of the pyranoside are more reactive, allowing anomeric distinction according to the relative abundance of the oxocarbenium product ion of this reaction in the spectrum. The higher reactivity of trans isomers is rationalized by neighboring group assistance that is possible only in the trans configuration. DFT calculations indicate that the lesser energetic reaction path occurs in an ammonium-cationized trans diequatorial 2,3-diacetoxy tetrahydropyran that was used as a model in order to study this process theoretically. It is also found that the configuration at position 4 of the carbohydrate plays a major role in the rate of formation and stability of oxocarbenium ions.

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Section: All Six Isomers Produce High Intensities Of [M C Nh 4 ]mentioning

confidence: 97%

Anomeric distinction and oxonium ion formation in acetylated glycosides

Denekamp

Sandlers

2005

J. Mass Spectrom.

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“…[14,15] for notation details). Upon reviewing previous work it has been concluded [8] that the hydrolysis of methyl Most interestingly, it is found that the oxygen in the pyranose ring becomes "desolvated" upon double bond/oxocarbenium formation, whereas it is engaged in the hydrogen-bonded water network before and after this period. This demonstrates that hydrogen bonding and thus the aqueous solvent play an active role in this reaction implying that microsolvation studies in the gas phase, both theoretical and experimental, might lead to qualitatively different reaction mechanisms compared to solution.…”

Section: Introductionmentioning

confidence: 94%

“…Simple sugars make up a wide variety of substances found in nature, from DNA to cellulose to biological energy storage mechanisms. Consequently, the glycosidic bond has been studied experimentally for a wide variety of compounds, [1][2][3][4][5][6][7][8][9][10][11][12][13] predominantly through hydrolysis, under a myriad of conditions, and is important in the consideration of enzymatic glycosyl-transfer reactions. One of the reasons it has been studied so extensively is because of the rich and often subtle variety of the reactions that take place.…”

Section: Introductionmentioning

confidence: 99%

“…This is similar to the proposed transition states for corresponding hydrolysis of methyl b-d-glucopyranoside. [1,2,8] At the transition state the C 1 -O 1 distance was % 1.9 indicating the degree of bond C 1 the transition state must be regarded as an early one, which is consistent with a late transition state for the back reaction. [2,5,6] The stability range of the oxocarbenium cation can also be roughly inferred from the shape of the free energy profile, see Figure 8, from values of x close to the maximum (where the transition state exists).…”

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confidence: 97%

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Aspects of Glycosidic Bond Formation in Aqueous Solution: Chemical Bonding and the Role of Water

Stubbs

Marx

2005

Chemistry A European J

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A model of the specific acid-catalyzed glycosidic bond formation in liquid water at ambient conditions is studied based on constrained Car-Parrinello ab initio molecular dynamics. Specifically the reaction of alpha-D-glucopyranose and methanol is found to proceed by a D(N)A(N) mechanism. The D(N) step consists of a concerted protonation of the O(1) hydroxyl leaving group; this process results in the breaking of the C(1)-O(1) bond, and oxocarbenium ion formation involving C(1)=O(5). The second step, A(N), is the formation of the C(1)-O(m) glycosidic bond, deprotonation of the methanol hydroxyl group O(m)H(m), and re-formation of the C(1)-O(5) single bond. A focus of this study is the analysis of the electronic structure during this condensed phase reaction relying on both Boys/Wannier localized orbitals and the electron localization function ELF. This analysis allows the clear elucidation of the chemical bonding features of the intermediate bracketed by the D(N) and A(N) steps, which is a non-solvent equilibrated oxocarbenium cation. Most interestingly, it is found that the oxygen in the pyranose ring becomes "desolvated" upon double bond/oxocarbenium formation, whereas it is engaged in the hydrogen-bonded water network before and after this period. This demonstrates that hydrogen bonding and thus the aqueous solvent play an active role in this reaction implying that microsolvation studies in the gas phase, both theoretical and experimental, might lead to qualitatively different reaction mechanisms compared to solution.

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“…It was proposed [22] that an enhanced anomeric effect is smaller for the S-C-F system than for the O-C-F system, leading to a smaller ground state stabilization for the S-C-F system. The mechanism of reactions of substrates containing these ring substituents has been reviewed [23]. …”

Section: Introductionmentioning

confidence: 99%

Nucleophilic Participation in the Solvolyses of (Arylthio)methyl Chlorides and Derivatives: Application of Simple and Extended Forms of the Grunwald-Winstein Equations

Kevill¹,

Park²,

Park³

et al. 2012

COC

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The specific rates of solvolysis of chloromethyl phenyl sulfide [(phenylthio)methyl chloride] and its p-chloro-derivative have been determined at 0.0 °C in a wide range of hydroxylic solvents, including several containing a fluroalcohol. Treatment in terms of a two-term Grunwald-Winstein equation, incorporating terms based on solvent ionizing power (YCl) and solvent nucleophilicity (NT) suggest a mechanism similar to that for the solvolyses of tert-butyl chloride, involving in the rate-determining step a nucleophilic solvation of the incipient carbocation in an ionization process. A previous suggestion, that a third-term governed by the aromatic ring parameter (I) is required, is shown both for the new and for the previously studied related substrates to be an artifact, resulting from an appreciable degree of multicollinearity between I values and a linear combination of NT and YCl values.

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Mechanisms of glycopyranosyl and 5-thioglycopyranosyl transfer reactions in solution

Cited by 32 publications

References 107 publications

Anomeric distinction and oxonium ion formation in acetylated glycosides

Anomeric distinction and oxonium ion formation in acetylated glycosides

Aspects of Glycosidic Bond Formation in Aqueous Solution: Chemical Bonding and the Role of Water

Nucleophilic Participation in the Solvolyses of (Arylthio)methyl Chlorides and Derivatives: Application of Simple and Extended Forms of the Grunwald-Winstein Equations

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