Synthesis of 5-O-α- and -β-D-glucopyranosyl-D-glucofuranose and 5-O-α-D-glucopyranosyl-D-fructopyranose (leucrose)

Reaction of 1,2-O-cyclopentylidene-α-D-glucofuranurono-6,3-lactone (2) with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide (1) gave 1,2-O-cyclopentylidene- 5-O-(2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl)-α-D-glucofuranurono-6,3-lactone (3, 45%) and 1,2-O-cyclopentylidene-5-O-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-α-D-glucofuranurono-6,3-lactone (4, 38%). Reduction of 3 and 4 with lithium aluminium hydride, followed by removal of the cyclopentylidene group, afforded 5-O-α-(9) and -β-D-glucopyranosyl-D-glucofuranose (12), respectively. Base-catalysed isomerization of 9 yielded crystalline 5-O-α-D-glucopyranosyl-D-fructopyranose (leucrose, 53%)

Synthesis of 5-O-β-D-galactofuranosyl-D-galactofuranose

Conversion of benzyl alpha beta-D-galactofuranoside into the 5,6-O-[α-(dimethyl-amino)benzylidene] derivative, followed by acetylation of HO-2 and HO-3, and selective ring opening or the acetal, gave benzyl 2,3-di-O-acetyl-6-O-benzoyl-α β-D-galactofuranoside (4). The title disaccharide was synthesised from 4 by reaction with 3,4,6-tri-O-acetyl-α-D-galactofuranose 1,2-(methyl orthoacetate) followed by removal of protecting group

Acid-catalysed hydrolysis of 1,2-O-alkylidene-α-D-glucofuranoses

The rates of acid-catalysed hydrolysis of 1,2-O-alkylidene-alpha-D-glucofuranoses indicate that, for oligosaccharide synthesis, cyclopentylidene and cycloheptylidene acetals are better protecting groups than the isopropylidene residue. Hydrolysis was impeded by a nitrate group at position 5 and more so by one at position 3. The hydrolyses were accompanied by a positive drift in optical rotation, except for the 5-O-substituted compounds where the formation of D-glucopyranose derivatives cannot occur

A facile preparation of alkyl α-glycosides of the methyl ester of N-acetyl-D-neuraminic acid

The reaction of methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-2-chloro-2,3,5-trideoxy-β-D-glycero-D-galacto-2-nonulopyranosonate with primary and secondary alcohols in the presence of silver salicylate affords, after O-deacetylation, stereo-specifically the corresponding methyl (alkyl 5-acetamido-3,5-dideoxy-α-D-glycero-D-galacto-2-nonulopyranosid)onates. The preparation of methyl(neopentyl 5-acetamido-3,5-dideoxy-α-D-glycero-D-galacto-2-nonulopyranosid)onate in benzene solution shows that this glycosylation can be carried out in an inert solvent

The synthesis of 5-O-(2-acetamido-2-deoxy-α-D-glucopyranosyl)-β-D-glucofuranose

Condensation of dimeric 3,4,6-tri-O-acetyl-2-deoxy-2-nitroso-α-D-glucopyranosyl chloride (1) with 1,2-O-isopropylidene-α-D-glucofuranurono-6,3-lactone (2) gave 1,2-O-isopropylidene-5-O-(3,4,6-tri-O-acetyl-2-deoxy-2-hydroxyimino-α-D-arabino-hexopyranosyl)-α-D-glucofuranurono-6,3-lactone (3). Benzoylation of the hydroxyimino group with benzoyl cyanide in acetonitrile gave 1,2-O-isopropylidene-5-O-(3,4,6-tri-O-acetyl-2-benzoyloxyimino-2-deoxy-α-D-arabino-hexopyranosyl)-α-D-glucofuranurono-6,3-lactone (4). Compound 4 was reduced with borane in tetrahydrofuran, yielding 5-O-(2-amino-2-deoxy-α-D-glucopyranosyl)-1,2-O-isopropylidene-α-D-glucofuranose (5), which was isolated as the crystalline N-acetyl derivative (6). After removal of the isopropylidene acetal, the pure, crystalline title compound (10) was obtained

A novel method for the structural and configurational analysis of alkyl 3,4,6-tri-O-acetyl-2-deoxy-2-hydroxyimino-α-D-arabino- and -lyxo-hexopyranosides, using E.P.R. spectroscopy

Alkyl 3,4,6-tri-O-acetyl-2-deoxy-2-hydroxyimino-α-D-arabino- and -lyxo-hexopyranosides were oxidised with lead(IV) acetate in solution, yielding the corresponding Z- and E-isomeric iminoxy radicals ( > C=N---O), which gave very intense and persistent electron paramagnetic resonance (e.p.r.) signals. Applyina previous results for cyclohexane iminoxy radicals and the differences between the spectra of the arabino and lyxo compounds, it has been possible to assign the observed, hydrogen hyperfine structure for both Z- and E-radicals to the hexopyranoid-ring hydrogen atoms at C-1,3,4, and 5 or 6. From Z- and E-oximes, the same Z/E-equilibrium mixture of iminoxy radicals is obtained. Also, conclusions on the conformation of the hexopyranoid ring have been drawn, based on solvent and temperature effects. The specificity and sensitivity ofthe novel e.p.r. method have been used to characterise α-D-oximes in μg-amounts in t.l.c. The presence of other (mainly β) oximes has also been demonstrated