NMR spectra of peracetylated methyl D-hexopyranosides and their 2-acetamido-2-deoxy derivatives in the presence of an europium shift reagent

Fluorinated carbohydrates as potential plasma membrane modifiers and inhibitors. Synthesis of 2-acetamido-2,6-dideoxy-6-fluoro-D-galactose

Reaction of benzyl 2-acetamido-3,4-di-O-benzyl-2-deoxy-6-O-mesyl-alpha-D-galactopyran oside with cesium floride gave benzyl 2-acetamido-3,6-anhydro-4-O-benzyl-2-deoxy-alpha-D-galactopyranoside instead of the desired 6-fluoro derivative. Acetonation of benzyl 2-acetamido-2-deoxy-6-O-mesyl-alpha-D-galactopyranoside gave the corresponding 3,4-O-isopropylidene derivative. The 6-O-mesyl group was displaced by fluorine with cesium fluoride in boiling 1,2-ethanediol, and hydrolysis and subsequent N-acetylation gave the target compound. In another procedure, treatment of 2-acetamido-1,3,4-tri-O-acetyl-2-deoxy-alpha-D-galactose with N-(diethylamino)sulfur trifluoride gave 2-acetamido-1,3,4-tri-O-acetyl-2,6-dideoxy-6-fluoro-D-galactose which, on acid hydrolysis followed by N-acetylation, gave 2-acetamido-2,6-dideoxy-6-fluoro-D-galactose.

The assignment of carbonyl resonances in 13C-n.m.r. spectra of peracetylated mono- and oligo-saccharides containing D-glucose and D-mannose: an alternative method for structural determination of complex carbohydrates

In the present study, proton homonuclear (COSY) and 13C-1H heteronuclear shift-correlation, n.m.r. spectroscopies have been used to assign the carbonyl carbon resonances of peracetylated D-gluco- and D-mannopyranose monosaccharides and oligosaccharides containing residues of parent D-glucopyranose monomers. Chemical shifts of these assigned resonances, particularly those arising from acetyl groups near to aglycon substitution sites, were found to be sensitive to the position and configuration of glycosidic linkages present. In addition, evidence is presented that indicates that the shifts of these carbonyl carbon resonances depend on long-range interactions with other peracetylated pyranose monomers resulting from folding of the oligosaccharide chain. These results suggest that carbonyl carbon resonances of peracetylated carbohydrates may be useful probes of oligosaccharide structure.

Modifications at C-3 and C-4 of 2-amino-2-deoxy-D-glucose

Modifications at C-3 and C-4 of 2-amino-2-deoxy-D-glucose have been developed. A 3,4-double bond was introduced into benzyl 2-acetamido-2-deoxy-3,4-di-O-methylsulfonyl-alpha-D-glucopyranoside by treatment with NaI and Zn. Epoxidation of the double bond with m-chloroperoxybenzoic acid gave an exo-epoxide exclusively. The stereochemistry of the epoxidation product has been confirmed by an alternative synthesis. An analysis of the 1H-n.m.r. spectra indicates that both the 3,4-unsaturated derivatives and the epoxide exist in the OH1 (D) conformation. Nucleophilic reagents (F-, I-) opened the 3,4-epoxide to give 4-substituted derivatives having the D-gulo configuration. Thus, 2-acetamido-1,3,6-tri-O-acetyl-2,4-dideoxy-4-iodo-alpha-D-gulopyranose and 2-acetamido-1,3,6-tri-O-acetyl-3,4-dideoxy-4-fluoro-alpha-D-gulopyranose have been synthesized. Reduction of the double bond in the key intermediate and deprotection gave 2-acetamido-2,3,4-trideoxy-D-glucopyranose. Some of the derivatives were active as inhibitors of growth of mouse, mammary adenocarcinoma cells in culture.