From methyl mannosides to methyl octosides by a stepwise homologation with Grignard C(1) reagents.

A four-step procedure for homologation of methyl alpha-D-mannofuranoside and alpha-D-mannopyranoside was examined. The reactions consisted in (i) oxidation of the terminal hydroxymethyl group in a protected sugar derivative to an aldehyde; (ii) reaction with allyloxymethylmagnesium chloride (or (phenyldimethyl)silylmethyl-magnesium chloride); (iii) protection of the newly formed secondary alcohol group; (iv) deprotection of the terminal CH(2)OR (or oxidation of the CH(2)SiMe(2)Ph) group. From methyl alpha-D-mannosides, stereoisomeric DalphaD and LalphaD methyl heptosides and from them, methyl octosides of D-threo- and L-erythro-alpha-D-manno configuration were obtained.

Homologation of methyl 2-azido- and 2-acetamido-3,4-di-O-benzyl-2-deoxy-D-hexopyranosides with allyloxymethylmagnesium chloride.

Methyl 2-azido-2-deoxy-hexodialdo-1,5-pyranosides of the alpha-, beta-D-gluco and alpha-D-manno configuration as well as methyl 2-acetamido-2-deoxy-hexodialdo-1,5-pyranosides of the alpha- and beta-D-gluco configuration, protected at positions 3 and 4 with O-benzyl groups were reacted with an excess of allyloxymethylmagnesium or (phenyldimethylsilyl)methylmagnesium chlorides to afford mixtures of C-6 stereoisomeric heptopyranosides. Configuration of the products separated by column chromatography was assigned by 1H NMR data.

Distribution of pyranose and furanose forms of 6-deoxyheptoses in water solution.

On the basis of 1H and 13C NMR spectroscopy studies, the proportion of pyranose and furanose forms of 6-deoxyheptoses in water solution was determined. Water solution of 6-deoxyheptoses contains all possible furanose and pyranose forms (except 6-deoxy-gluco-heptose for which only pyranose was found), although pyranose is dominant.

Synthesis and serological characterization of L-glycero-alpha-D-manno-heptopyranose-containing di- and tri-saccharides of the non-reducing terminus of the Escherichia coli K-12 LPS core oligosaccharide.

Synthesis of the title trisaccharide was accomplished by sugar chain extension starting from the non-reducing terminus: coupling of Glcp NAc with LD-Hepp, then adding Glcp-OAll. An alternative route started from the reducing end: coupling of LD-Hepp with Glcp-OAll, then addition of Glcp NAc. In the synthesis of the title disaccharide a modification of the first approach was employed.

Configuration of heptopyranoside and heptofuranoside side chains: 2-anthroate, a powerful chromophore for exciton coupled CD.

The absolute configuration of the acyclic side chain of heptopyranosides and heptofuranosides was determined by exciton coupled CD, employing the strongly fluorescent 2-anthroate chromophore. The usage of this chromophore offers significant improvements over previous chemical and spectroscopic procedures since its intense fluorescence greatly facilitates the isolation and HPLC purification at the nanogram scale. The large amplitudes of the bisignate spectra allow CD manipulations in the 1 x 10(-7) M range.