Conformation of the galactose ring adopted in solution and in crystalline form as determined by experimental and DFT 1H NMR and single-crystal X-ray analysis |
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Authors: | Roslund Mattias U Klika Karel D Lehtilä Reko L Tähtinen Petri Sillanpää Reijo Leino Reko |
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Institution: | Department of Organic Chemistry, Abo Akademi University, Biskopsgatan 8, FIN-20500 Abo, Finland. mattias.roslund@abo.fi |
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Abstract: | The solution-state conformations of various galactose derivatives were determined by comparison of the experimental (1)H-(1)H vicinal coupling constants to those calculated using density functional theory (DFT) at the B3LYP/cc-pVTZ//B3LYP/6-31G(d,p) level of theory. The agreement between the experimental and calculated vicinal coupling constants for 1,2:3,4-di-O-isopropylidene-alpha-d-galactopyranose was good, thereby confirming an (O)S(2) skew conformation for it and its derivatives on the basis of their similar observed couplings. Single-crystal X-ray analysis of 1,2:3,4-di-O-isopropylidene-6-O-(3,4,6-tri-O-acetyl-2-deoxy-2-N-phthalimido-beta-d-glucopyranosyl)-alpha-d-galactopyranose and 1,2,3,4,6-penta-O-acetyl-alpha-d-galactopyranose provided (O)S(2) and (4)C(1) conformations, respectively, for the galactose ring in the solid state. The solid-state structures proved to be suitable starting structures for further DFT structure refinement or for immediate calculation of the coupling constants. |
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