Theoretical study on the anomeric effect in α-substituted tetrahydropyrans and piperidines

Martins, Francisco A.; Silla, Josué M.; Freitas, Matheus P.

doi:10.1016/j.carres.2017.09.007

Cited by 20 publications

(21 citation statements)

References 29 publications

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“…At this stage, the attribution of all the signals of the intricate 1 H spectrum displayed in Figure a is a very delicate task. Unexpectedly, the addition of CHCl 3 [5 mL for 3.5 mmol (0.4 g) of initially added DVG] at 0 °C on the resulting oil (crude product) obtained after evaporation of diethyl ether provokes the selective precipitation of the diastereoisomer 1 of L 6 L 6 resulting from the meso ‐DVG (Figure ) , . Its NMR spectrum allows attribution of all protons of this isomer (Figure b) by comparison with previous data from Burton and Pomin .…”

Section: Resultsmentioning

confidence: 54%

cRh‐Catalyzed Hydroformylation of Divinylglycol: An Effective Way to Access 2,7‐Dioxadecalin‐3,8‐diol

et al. 2019

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Section: Resultsmentioning

confidence: 54%

cRh‐Catalyzed Hydroformylation of Divinylglycol: An Effective Way to Access 2,7‐Dioxadecalin‐3,8‐diol

et al. 2019

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“…This is similar to the case of some α-substituted tetrahydropyrans and piperidines. 14 In order to investigate the role of overall electron delocalization in the conformational stabilities, an energy-partitioning scheme named NEDA (natural energy decomposition analysis) was carried out and the contributions from hyperconjugation and Lewis-type (steric and electrostatic) interactions to the overall conformational energies through the NBO framework are given in Table 3. Accordingly, the G–g+/cl/g– conformer of α- d -glucose is less stabilized by non-Lewis-type interactions than the remaining α-anomers, but it is more destabilized because of Lewis-type interactions than the cc β-anomers.…”

Section: Resultsmentioning

confidence: 99%

“…The most remarkable interaction affecting the stereochemistry of this class of compounds is the anomeric effect, according to which the α-anomer of a pyranoside ring is surprisingly stable if only traditional steric effects are taken into consideration. 13,14 The gauche effect is also important for the conformational preferences in cyclic sugars because these systems bear vicinal electronegative groups that tend to be arranged in a gauche orientation because of hyperconjugative interactions. 15 Nevertheless, another interesting and controversial conformational finding in d -glucose is the counterclockwise (cc) preference for the orientation of the hydroxyl groups.…”

Section: Introductionmentioning

confidence: 99%

Revisiting the Case of an Intramolecular Hydrogen Bond Network Forming Four- and Five-Membered Rings in d-Glucose

Martins

Freitas

2018

ACS Omega

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The conformational behavior of cyclic monosaccharides has been widely studied over the past years, but there is no general agreement about which effects are in fact responsible for the observed conformational preferences. A recent microwave spectroscopy study determined the conformational equilibrium of d -glucose in the gas phase with a preference for a counterclockwise arrangement of the hydroxyl groups. Nevertheless, the effects that control this orientation are still uncertain because the role of intramolecular hydrogen bonds (IHBs), electrostatic and steric repulsions is not clear. This work reports a density functional theory approach based on the conformational energies of d -glucose and of some derivatives in which the anomeric hydroxyl is replaced with hydrogen (H, small and not prone to participate in proton transfer), fluorine (F, small, electronegative, and as capable as OH of forming hydrogen bonds as a proton acceptor), and chlorine (Cl, big and not anticipated to be involved in effective hydrogen bond formation) to obtain insights into the effects of the substituent at the anomeric carbon on the arrangement of the hydroxyl groups in d -glucose. The nature of the substituents at this position is crucial to determine the orientation of the remaining hydroxyl groups. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses, in addition to NMR chemical shift calculations, have been provided to support the conformational energy outcomes. Overall, the results agree with the lack of IHBs forming four- and five-membered rings in d -glucose and emphasize that steric and electrostatic repulsions involving the hydroxyl groups in the clockwise orientation are driving forces of the conformational behavior.

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“…[77,81] Theoretical studies on the conformational behavior of 2-fluoropiperidines have been conducted as well (Figure 12 A). [82,83] There are four possible conformers for 2-fluoropiperidine 64, where the axial-equatorial conformer (64 ax,eq ) is calculated to be the lowest energy conformer in both gas phase and DMSO. [82] This is owing to the existence of endocyclic nitrogen, an electron donor, which enables an effective nn!s* CÀF hyperconjugative interaction, that is, endo-anomeric effect, and hence sufficiently stabilizes the axial-equatorial conformer 64 ax,eq .…”

Section: Fluorine Orientation In Five-membered Ringsmentioning

confidence: 99%

Fluorinated Rings: Conformation and Application

Mondal

Agbaria

Nairoukh

2021

Chemistry A European J

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The introduction of fluorine atoms into molecules and materials across many fields of academic and industrial research is now commonplace, owing to their unique properties. A particularly interesting feature is the impact of fluorine substitution on the relative orientation of a C−F bond when incorporated into organic molecules. In this Review, we will be discussing the conformational behavior of fluorinated aliphatic carbo‐ and heterocyclic systems. The conformational preference of each system is associated with various interactions introduced by fluorine substitution such as charge‐dipole, dipole‐dipole, and hyperconjugative interactions. The contribution of each interaction on the stabilization of the fluorinated alicyclic system, which manifests itself in low conformations, will be discussed in detail. The novelty of this feature will be demonstrated by presenting the most recent applications.

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Theoretical study on the anomeric effect in α-substituted tetrahydropyrans and piperidines

Cited by 20 publications

References 29 publications

cRh‐Catalyzed Hydroformylation of Divinylglycol: An Effective Way to Access 2,7‐Dioxadecalin‐3,8‐diol

cRh‐Catalyzed Hydroformylation of Divinylglycol: An Effective Way to Access 2,7‐Dioxadecalin‐3,8‐diol

Revisiting the Case of an Intramolecular Hydrogen Bond Network Forming Four- and Five-Membered Rings in d-Glucose

Fluorinated Rings: Conformation and Application

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