THE CONFIGURATION OF GLYCOSIDIC LINKAGES IN OLIGOSACCHARIDES: VII. 4-O-β-D-GALACTOPYRANOSYL-D-GALACTOSE FROM WHITE BIRCH WOOD

Abstract

Partial acid hydrolysis of an a-cellulose prepared fro111 white birch (Betula papyrifera) wood has led to the isolation of a new disaccharide (1). The disaccharide is now shown to be 4-0-P-D-galactopyranosyl-D-galactose.

Directed and Efficient Syntheses of β(1→4)-Linked Galacto-Oligosaccharides

“…Ϫ Column chromatography was carried out on Fluka silica gel 60 (70Ϫ230 mesh); eluents are given in brackets. Ϫ 1 H and 13 C NMR spectra were recorded on Bruker WM 300, AC 300, and AVANCE 500 spectrometers. The structures of all new compounds were confirmed by COSY, TOCSY, selective TOCSY, and/or decoupling experiments.…”

“…Coupling constants are listed separately if an assignment was possible. In the listings of 1 H and 13 1 H NMR, C-1a, C-1b, etc. for 13 C NMR spectroscopic data.…”

“…Configurational assignments of the intersaccharidic linkages having readily been settled on the basis of 1 H NMR spectroscopic data (supporting information may be derived from the reported 13 C NMR spectroscopic data, which warrants little comment), confirmation of starch-like coiling within the linear oligogalactoside chains, strongly suggested both by analogy considerations (Figure 1) and by various molecular modelling approaches, [20Ϫ24] did not materialise. At present, none of the higher galactooligosaccharides has proved obtainable in crystalline form to allow X-ray structural investigations, either as a free sugar or as a p-methoxyphenyl derivative.…”

“…However, their isolation from pectic cell wall material is exceedingly cumbersome and has rarely provided well defined products Ϫ exceptions being mg quantities of galactobiose, [13] -triose, and -tetraose. [12] Similarly, the generation of oligo-β(1Ǟ4)-galactosides by β-galactosidase-induced galactosyl transfer has, despite its simplicity, not passed the β(1Ǟ4)-galactobiose stage, [32,33] while their chemical synthesis has proven to be a particularly formidable task, since the axially disposed 4-OH of a galactosyl acceptor, necessarily carrying blocking groups at O-6 and O-3, is sterically less accessible for glycosylation than primary or equatorial OHs, aside from its being comparatively unreactive to begin with.…”

SYNTHESIS OF 4-O-β-D-GALACTOPYRANOSYL-D-GALACTOSE

“…The two disaccharides 4-0-P-D-galactopyranosyl-D-galactose (I) and 6-O-@-~-galact~-p y r a n o s y l -~-g a l a c t~~e (11) have been isolated fro111 the partial hydrolysis products of polysaccharides (1,2). The disaccharide (11) had earlier been synthesized by the condensation of acetobromo-D-galactose with 1,2;3,4-di-0-isopropylidene-D-galactose followed by acidic hydrolysis of the isopropylidene residues (3).…”