PREPARATION OF α AND Β ANOMERS OF VARIOUS ISOMERIC METHYL O-D-GALACTOPYRANOSYL-D-GALACTOPYRANOSIDES. STANDARDS FOR INTERPRETATION OF 13C-N.M.R. SPECTRA OF D-GALACTOPYRANANS

Article abstract of DOI:10.1016/S0008-6215(00)80790-9

The four isomer of methyl O-β-D-galactopyranosyl-β-D-galactopyranoside were prepared by condensation of 2,3,4,6-tetra-O-acetyl-α-galactopyranosyl bromide with appropriate, partially O-substitued derivatives of methyl β-D-galactopyranoside.Reaction of 3,4,6-tri-O-acetyl-1,2-O-(1-ethoxyethylidene)-α-D-galactopyranose with the same acceptors, in the presence of mercuric bromide, led to the formation of α and β linkages.Thus, it was possible to assign 13C-n.m.r. resonances of α and β anomers of methyl O-D-galactopyranosyl-β-D-galactopyranosides.In terms of application of these shift values and those of related D-galactobioses to the structual analysis of D-galactopyranans by shift comparisons, some generalizations can be made.For β-D-galactopyranans, the resonances glycosyloxylated carbon atoms of methyl O-β-D-galactopyranosyl-β-D-galactopyranosides are sensitive to structure and appear to have typical values, whereas limited variation was observed with shift of C-1' signals.On the other hand, for assigning structures to D-galactopyranans containing α linkages, the C-1' shifts (at higher field) of methyl O-α-D-galactopyranosyl-β-D-galactopyranosidesc are sensitive to linkage position, whereas those of glycosyloxylated carbon atoms vary only a little.