Experimental and theoretical evaluation of trans-3-halo-2-hydroxy-tetrahydropyran conformational preferences. Beyond anomeric interaction

RSC Advances ◽  
2015 ◽  
Vol 5 (45) ◽  
pp. 35412-35420 ◽  
Author(s):  
Thaís M. Barbosa ◽  
Renan V. Viesser ◽  
Raymond J. Abraham ◽  
Roberto Rittner ◽  
Cláudio F. Tormena
Keyword(s):  
Anomeric Effect ◽  
Theoretical Evaluation ◽  
Conformational Preferences

Which analysis will explain the preferences of the substituents in the hydro-halo-tetrahydropyran rings? Is the anomeric effect essential to understand what is going on?

Conformational Preferences of Ethyl 2,3-Dideoxy-3-[(α-D-glucopyranosyl)methyl]-β-L- and -D-arabino-hexopyranosides

2005 ◽  
Vol 70 (12) ◽  
pp. 2086-2100 ◽  
Author(s):  
Ondřej Vích ◽  
Ladislav Kniežo ◽  
Hana Dvořáková ◽  
Ivan Raich ◽  
Štěpán Valenta
Keyword(s):  
The Other ◽  
Glycosidic Bond ◽  
Conformational Behavior ◽  
Anomeric Effect ◽  
Conformational Preference ◽  
Other Hand ◽  
Conformational Preferences

Conformational behavior of two C-disaccharides, containing D-glucopyranose moiety at the non-reducing end and L- or D-2-deoxy-arabino-hexopyranose moiety at the reducing end, has been studied using MM3 calculations and NMR experiments. The obtained results show that the conformational preference around the C-glycosidic bond is the same in both compounds and corresponds with the exo-anomeric effect. On the other hand, both compounds differ markedly in the conformational arrangement around the C-aglycone bond where the population of conformers is controlled by 1,3-diaxial-like interactions.

Experimental and theoretical evaluation on the conformational behavior of l-aspartic acid dimethyl ester and its N-acetylated derivative

RSC Advances ◽  
2015 ◽  
Vol 5 (23) ◽  
pp. 18013-18024 ◽  
Author(s):  
Carolyne B. Braga ◽  
Lucas C. Ducati ◽  
Roberto Rittner
Keyword(s):  
Aspartic Acid ◽  
Dimethyl Ester ◽  
Intramolecular Interactions ◽  
Conformational Behavior ◽  
Theoretical Evaluation ◽  
Acid Dimethyl Ester ◽  
Conformational Preferences

The AspOMe and AcAspOMe conformational preferences and their corresponding intramolecular interactions were studied through spectroscopic and theoretical methodologies.

Concerning the conformational preferences of the 2-cyano derivatives of oxane, thiane, and selenane

2010 ◽  
Vol 88 (8) ◽  
pp. 831-838 ◽  
Author(s):  
Michael H. Benn ◽  
Yan Yan Huang ◽  
Frank Johannsen ◽  
Michael O’Reilly ◽  
Masood Parvez ◽  
...  
Keyword(s):  
Bond Length ◽  
Cyano Group ◽  
Lone Pair ◽  
Nbo Analysis ◽  
Orbital Interaction ◽  
Anomeric Effect ◽  
Model Compounds ◽  
Conformational Preferences ◽  
Lone Pair Electrons ◽  
Derivatives Of

This paper investigates the origin of the anomalous anomeric effect in merosinigrin, a 2-cyanothiane in which the cyano group is axial as expected for the anomeric effect, but in which bond distances are opposite to that expected from the nS→[Formula: see text] orbital interaction, which underlies the classical anomeric effect. The model compounds, 2-cyanooxane, 2-cyanothiane, and 2-cyanoselenane, were synthesized and studied both experimentally and computationally. Both the thia and selena systems displayed an even higher preference for the axial conformation than the oxa system but also exhibited the bond length anomalies found previously in merosinigren. Natural bond order (NBO) analysis of the B3LYP/6–311+G(3df,2p) wave functions of the axial and equatorial forms of the three systems confirmed a weakening of the n→σ* orbital interaction in the O, S, and Se series, and a strengthening of a σ–π*(CN) interaction that explains the bond length reversals observed in the S and Se systems. It also revealed a new mechanism, n→π*, namely, a through-space interaction between the nonbonded lone pair electrons of the heteroatom and the π* orbital of the cyano group, which selects for the axial conformation.

Ab initio DFT calculations of the configurational and conformational preferences of 2-phenylsulfinylcyclohexanones — Evidence for "exo-anomeric" interactions

2006 ◽  
Vol 84 (4) ◽  
pp. 685-691 ◽  
Author(s):  
Melissa L Trapp ◽  
John F Wojcik ◽  
Walter W Zajac, Jr. ◽  
B Mario Pinto
Keyword(s):  
Dft Calculations ◽  
Ab Initio ◽  
High Energy ◽  
The Other ◽  
Carbonyl Carbon Atom ◽  
Torsional Angle ◽  
Orbital Interaction ◽  
Anomeric Effect ◽  
Orbital Interactions ◽  
Conformational Preferences

The conformational analysis of 2-phenylsulfinylcyclohexanone by ab initio density functional calculations is described. Six conformations corresponding to axial/equatorial isomers and rotation about the exocyclic C2—S bond in each of the RR or RS diastereomers were calculated and the results were examined in terms of relative energies, electrostatic interactions, orbital interactions, and geometrical variations. The global minimum conformation was the RS isomer that positioned the phenylsulfinyl moiety in an equatorial orientation and the sulfinyl oxygen in an anti orientation with respect to the carbonyl carbon atom. Of the other three low energy conformations, only one had a gauche arrangement of these atoms, and only in one of the four lower energy conformations was evidence found for a S-O(–)···C(+)-O electrostatic interaction. In contrast, the results were consistent with the operation of nS → [Formula: see text] stabilizing orbital interactions. Further support for this hypothesis was obtained from the increased C=O bond lengths in these four conformations relative to the other conformations, and by the torsional angle distortion away from ideal geometry, presumably to maximize the stabilizing orbital interaction. We propose that this conformational preference is a manifestation of a generalized exo-anomeric effect. The longer C2—S bond in the axial isomers was also interpreted in terms of a stabilizing πC=O → [Formula: see text] interaction, analogous to an endo-anomeric interaction. Comparison of the computational results to available experimental data on the conformational equilibrium of each diastereomer in solution suggests which conformers are present in each of the equilibria. The available data for the solid state indicate that the RR and RS isomers both crystallize in high energy conformations, stabilized by intermolecular interactions.Key words: 2-phenylsulfinylcyclohexanones, configurational isomers, conformational preferences, DFT calculations, exo-anomeric effect.

Conformational preferences in glycosylamines. Implications for the exo-anomeric effect

2001 ◽  
Vol 330 (3) ◽  
pp. 421-426 ◽  
Author(s):  
Raymond J. Batchelor ◽  
David F. Green ◽  
Blair D. Johnston ◽  
Brian O. Patrick ◽  
B.Mario Pinto
Keyword(s):  
Anomeric Effect ◽  
Conformational Preferences

The Importance of the Pauli Exchange-Type Repulsions and Hyperconjugative Interactions on the Conformational Properties of Halocarbonyl Isocyanates and Halocarbonyl Azides

2017 ◽  
Vol 70 (1) ◽  
pp. 61 ◽  
Author(s):  
Athena Behrouz ◽  
Davood Nori-Shargh
Keyword(s):  
Electrostatic Interactions ◽  
Basis Set ◽  
Anomeric Effect ◽  
Electrostatic Model ◽  
Open Chain ◽  
Cooperative Effects ◽  
Barrier Heights ◽  
Conformational Preferences ◽  
Conformational Properties ◽  
Cis And Trans

To gain further insight into the origin of the anomeric relationships in planar open-chain (acyclic) compounds, we examined the effects of the hyperconjugative generalized anomeric effect (HC-GAE), Pauli exchange-type repulsion (PETR), the electrostatic model associated with the dipole–dipole interactions (EM-DDI), and the attractive electrostatic interactions (AEI) between the natural atomic charges (NACs) on the conformational properties of halocarbonyl isocyanates [halogen = F (1), Cl (2), Br (3)] and halocarbonyl azides [halogen = F (4), Cl (5), Br (6)] by means of G3MP2, CCSD, MP2, and B3LYP methods with the 6–311+G** basis set on all atoms and natural bond orbital interpretation. Importantly, the deletions of the through bond LPN3→σ*C2–X6 hyperconjugative interactions from the Fock matrices of the cis- and trans-conformations lead to the increase of the cis-conformations’ stability compared with their corresponding trans-conformations going from compound 1 to 3 and from compound 4 to 6, revealing the determining effects on the conformational preferences in compounds 1–3 and 4–6. Essentially, the effects of the through space (LPN3→σ*C4–O5 and LPNα→π*Nβ=Nω, respectively) hyperconjugative interactions on the conformational preferences in the isocyanate (1–3) and azide compounds (4–6) are negligible. The EM-DDI fails to account for the conformational preferences in compounds 2, 3, 5, and 6. Therefore, the generalized anomeric relationships in compounds 1–3 and 4–6 result from the cooperative effects of the HC-GAE and PETR. The variations of the AEIs revealed their opposite effects on the trend observed for the conformational preferences in compounds 1–3 and 4–6. Contrary to the usual assumption, the much larger barrier heights of the rotation around the C2–N3 bonds in the azide compounds (4–6) compared with those in the isocyanate compounds (1–3) result from the exchange components and have no hyperconjugative origin.

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