Comparative conformational studies of 3,4,6-tri-O-acetyl-1,5-anhydro-2-deoxyhex-1-enitols at the DFT level

Andrzej Nowacki , Beata Liberek

Abstract

B3LYP and M06–2X optimization and MP2 single point calculations are reported for the 4H5 and 5H4 conformations of 3,4,6-tri-O-acetyl-D-allal, 3,4,6-tri-O-acetyl-D-galactal, 3,4,6-tri-O-acetyl-D-glucal, and 3,4,6-tri-Oacetyl- D-gulal. Significant discrepancies in predictions of relative energies and conformers' population for B3LYP and M06–2X optimized geometries are observed. Generally, B3LYP overestimates the conformers' energies with respect to MP2, whereas M06–2X slightly underestimates the conformers' energies. B3LYP failed to estimate the 4H5⇄5H4 conformational equilibrium for 3,4,6-tri-O-acetyl-D-galactal and 3,4,6-tri-O-acetyl-D-glucal. The M06–2X functional showed good agreement with experimental results for all glycals studied. The 4H5⇄5H4 conformational equilibrium for 3,4,6-tri-O-acetyl-D-allal and 3,4,6-tri-O-acetyl-D-gulal is governed by the vinylogous anomeric effect (VAE), whereas competition between the VAE and quasi 1,3-diaxial interactions influence this equilibrium for 3,4,6-tri-O-acetyl-D-galactal and 3,4,6-tri-O-acetyl-D-glucal. The orientation of the 4- OAc group influences the strength of the quasi 1,3-diaxial interactions between the 3-OAc and 5-CH2OAc groups. AIM analysis shows weak bonding interaction between the 3-OAc and 5-CH2OAc groups.
Author Andrzej Nowacki PG
Andrzej Nowacki,,
- Laboratory of Glycochemistry
, Beata Liberek PG
Beata Liberek,,
- Laboratory of Glycochemistry
Journal seriesCarbohydrate Research, ISSN 0008-6215
Issue year2018
Vol462
Pages13-27
Publication size in sheets0.7
Keywords in Englishglycal, conformation, allylic effect, vinylogous anomeric effect, quasi 1,3-diaxial interactions, B3LYP, M06-2X
DOIDOI:10.1016/j.carres.2018.03.013
URL https://doi.org/10.1016/j.carres.2018.03.013
Languageen angielski
Score (nominal)25
ScoreMinisterial score = 25.0, 04-05-2018, ArticleFromJournal
Ministerial score (2013-2016) = 25.0, 04-05-2018, ArticleFromJournal
Publication indicators WoS Impact Factor: 2016 = 2.096 (2) - 2016=1.963 (5)
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