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.
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.
Roslund
Mattias U
MU
Department of Organic Chemistry, Abo Akademi University, Biskopsgatan 8, FIN-20500 Abo, Finland. mattias.roslund@abo.fi
Klika
Karel D
KD
Lehtilä
Reko L
RL
Tähtinen
Petri
P
Sillanpää
Reijo
R
Leino
Reko
R
D003460:Crystallization; D018360:Crystallography, X-Ray; D005690:Galactose / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011522:Protons; D012996:Solutions
D011522:Protons; D012996:Solutions; D005690:Galactose