SYNTHESIS AND CONFORMATIONAL-ANALYSIS OF (6R)-[6-H-2(1)]-1,2/3,4-DI-O-ISOPROPYLIDENE-ALPHA-D-GALACTOPYRANOSE - NMR AND MOLECULAR MODELING STUDIES

The conformation preferences of 1,2:3,4-di-O-isopropylidine-alpha-D-galactopyranose have been determined using NMR and molecular modeling (conformational searching) techniques. The pyranose ring assumes a skew-boat conformation. Coupling constants for the C-6 side chain and hydroxyl proton indicate that the predominant conformation places the oxygen anti to C-4 (gt conformation) with the hydroxyl aligned toward the pyranose oxygen in deuteriochloroform. A similar orientation of the C-5-C-6 bond was observed in water and toluene. In DMSO the C-6 oxygen is anti to the pyranose oxygen (tg conformation) with the hydroxyl hydrogen anti to C-5. A similar orientation of the C-5-C-6 bond was observed in methanol.