The optimized molecular structures, harmonic vibrational wavenumbers, and the corresponding vibrational assignments of (1S,2S)-tramadol and (1R,2R)-tramadol are computationally examined using the B3LYP density functional theory method together with the standard 6-311++G(d,p) and def2-TVZP basis sets. The optimized structures show that phenolic rings of both 1R,2R and 1S,2S tramadol adopt planar geometry, which are slightly distorted due to the substitution at the metaposition; and the six-membered cyclohexane adopts a slightly distorted chair conformation. The 1S,2S enantiomer is energetically more favorable than 1R,2R with the energy differences of 1.32 and 1.03 kcal/mol obtained at B3LYP/6-311++G (d,p) and B3LYP/Def2-TVZP levels, respectively. The analysis of the binding pocket in the silico molecular docking with the m-opioid receptor shows that it originated two clusters with the 1S,2S enantiomer and one cluster with the 1R,2R enantiomer of tramadol. The results point to a more stable complex of the m-opioid receptor with the 1R,2R enantiomer of tramadol.
K E Y W O R D SDFT, frontier molecular orbital, molecular docking, tramadol, vibrational spectra
Key indicatorsSingle-crystal X-ray study T = 298 K Mean (C-C) = 0.003 Å Disorder in main residue R factor = 0.057 wR factor = 0.118 Data-to-parameter ratio = 17.1 For details of how these key indicators were automatically derived from the article, see Molecules in the title crystal structure, C 20 H 24 O 4 , are linked into chains of R 4 4 (8) rings along [010] and these chains are linked into sheets via weak C-HÁ Á Á(arene) interactions. These sheets are, in turn, linked via weak C-HÁ Á Á(arene) and C-HÁ Á ÁO interactions into a three-dimensional network. The ethyl substituent is disordered over two sites with refined occupancies of 0.700 (5) and 0.300 (5).
Key indicatorsSingle-crystal X-ray study T = 298 K Mean (C-C) = 0.003 Å R factor = 0.045 wR factor = 0.113 Data-to-parameter ratio = 15.0 For details of how these key indicators were automatically derived from the article, see
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