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At least 19 recordsLinked to original sources
PubMed2005

De novo enantioselective syntheses of galacto-sugars and deoxy sugars via the iterative dihydroxylation of dienoate.

An efficient route to various sugar lactones has been developed. Key to the overall transformation is the sequential osmium-catalyzed dihydroxylation of 2,4-dienoates. The simplest (one-step/racemic) example of this reaction occurs when the dihydroxylation is performed with aqueous NMO in MeOH. When the first dihydroxylation is performed using the AD-mix procedure, an enantioselective variant results. When a matched AD-mix procedure is used for the second dihydroxylation, an exceedingly diastereo- and enantioselective synthesis of galacto-1,4-lactone results. [Reaction: see text]

Deoxy Sugars↗
PubMed1977

Photochemical conversion of sugar dimethylthiocarbamates into deoxy sugars.

Protected sugar derivatives having one free hydroxyl group may be deoxygenated at the alcoholic position by ultraviolet irradiation of the corresponding dimethylthiocarbamic esters; a concomitant process leads also to the original alcohol. Thus, on photolysis, the 6-dimethylthiocarbamate (1) of 1,2:3,4-di-O-isopropylidene-alpha-D-galactopyranose (3) gives 6-deoxy-1,2:3,4-di-O-isopropylidene-alpha-D-galactopyranose (2) together with 3. Likewise, the 4-dimethylthiocarbamate (6) of 1,6-anhydro-2,3-O-isopropylidene-beta-D-mannopyranose (8) gives a mixture of the 4-deoxy derivative 7 and the alcohol 8. 3-Deoxy-1,2:5,6-di-O-isopropylidene-alpha-D-ribo-hexofuranose (10) was obtained by irradiation of 3-O-(dimethylthiocarbamoyl)-1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose (9), and was accompanied by 1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose (11). The 3-deoxy-3-iodo analog (14) of 11 underwent conversion into 10 by photolysis, and the deoxy sugar 10 was also prepared from 3,3'-dithiobis(1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose) (12) by the action of Raney nickel. Photolysis of the 2-dimethylthiocarbamate (16) of methyl 3,4-O-isopropylidene-beta-L-arabinopyranoside (18 gave the 2-deoxy derivative (17), together with the parent alcohol 18, and the same pair of products was obtained by the action of tributylstannane on the 2-(methylthio)thiocarbonyl derivative (19) of 18, although the dimethylthiocarbamate 16 was unreactive toward tributylstannane.

Arabinose↗
PubMed1976

Transglycosylic reactions of nucleotides of deoxy sugars. Biosynthesis of deoxy analogues of alpha,alpha'-trehalose.

The biosynthesis of alpha,alpha'-trehalose was investigated in a reaction catalyzed with yeast UDP-Glc :glucose-6-phosphate 1-glucosyl transferase. It was revealed that the hydroxyls at positions C-2, C-3, C-4 and C-6 are not essential for preserving its substrate properties in this reaction. The affinity of the enzyme and the rate of hexose incorporation into trehalose decreases in following sequence: UDP-glucose, UDP-2-deoxy-D-glucose, UDP-6-deoxy-d-glucose, UDP-4-deoxy-D-glucose and UDP-3-deoxy-D-glucose.

Deoxy Sugars↗
PubMed1977

Determination of the linkages of disaccharides containing a 2-acetamido-2-deoxy sugar unit by solvent effects in circular dichroism.

The circular dichroism spectra of 2-acetamido-2-deoxy sugars in 1,1,1,3,3,3-hexafluoro-2-propanol (F6Pr-2-ol) solutions show a positive band in the n-pi region (209 nm) in contrast to a negative c.d. band in water solution. This difference is interpreted as an indication of a change in the average orientation of the hydroxyl groups adjacent to the amide group. C.d. spectra of 2-acetamido-2-deoxy sugars having a methyl group at O-1 and O-3 confirm this interpretation and suggest that the c.d. spectrum of a disaccharide in F6Pr-2-ol reflects strongly the disaccharide linkage. Large differences in the c.d. spectra of (1 leads to 4) and (1 leads to 6)-linked disaccharides in this solvent lead to rules for distinguishing the linkages of the disaccharides.

Acetylgalactosamine↗
PubMed2002

[Determination of the D- and L-configurations of amino deoxy sugars by (S)-TBMB carboxylic acid, a fluorescent chiral derivatization reagent].

D- and L- amino sugars were coupled with (S)-TBMB (S)-TBMB = (S)-2-tert-butyl-2-methyl-1, 3-benzodioxole carbonyl chloride, a fluorescent chiral reagent, followed by per-O-acetylation. The reactions yielded diastereomeric per-O-acetylated N-(S)-TBMB carbonyl amino sugars. Their (1)HNMR signals, especially the strong singlet peaks of tert-Bu and Me groups were diagnostic for the determination of the D-, L- configurations of amino sugar. Furthermore, a simple and highly sensitive method for the determination of the D-, L- configuration of amino deoxy sugars was developed based on the same fluorescent labeling method and reverse phase HPLC. The total time in analysis is less than two hours and the detection limit of the method is 0.2 picomolar.

Amino Sugars↗
PubMed1996

Substrate specificity of native dTDP-D-glucose-4,6-dehydratase: chemo-enzymatic syntheses of artificial and naturally occurring deoxy sugars.

Incubation of dTDP-glucose with the enzyme dTDP-glucose-4,6-dehydratase [EC 4.2.1.46] from wild type E. coli B yielded a mixture of 3- and 4-keto-6-deoxy sugars after work-up. Model experiments with chemically synthesized methyl 6-deoxy-4-keto-glucoside (9) revealed that dTDP-6-deoxy-alpha-D-ribo-hexopyran-3-ulose (3) is formed by keto-enol tautomerization during the isolation procedure from initially formed dTDP-6-deoxy-alpha-D-xylo-hexopyran-4-ulose (2). dTDP-3-deoxyglucose (4) and dTDP-3-azido-3-deoxyglucose (6) were substrates and showed Michaelis-Menten kinetics (4: KM = 200 microM and V(max) = 130 mumol/h mg; 6: KM = 300 microM and V(max) = 90 mumol/h mg). In 100-mg-scale experiments, both non-natural substrates gave the respective 6-deoxy-4-keto compounds, dTDP-3,6-dideoxy-alpha-D-erythro-hexopyran-4-ulose (5) and dTDP-3-azido-3,6-dideoxy-alpha-D-xylo-hexopyran-4-ulose++ + (7), in yields ranging from 24 to 40%.

Deoxy Sugars↗
PubMed1984

Reactivity of hydroxyl and hydroxyl-like radicals discriminated by release of thiobarbituric acid-reactive material from deoxy sugars, nucleosides and benzoate.

Hydroxyl radicals (OH.) can be formed in aqueous solution by a superoxide (O2.-)-generating system in the presence of a ferric salt or in a reaction independent of O2.- by the direct addition of a ferrous salt. OH. damage was detected in the present work by the release of thiobarbituric acid-reactive material from deoxy sugars, nucleosides and benzoate. The carbohydrates deoxyribose, deoxygalactose and deoxyglucose were substantially degraded by the iron(II) salt and the iron(III) salt in the presence of an O2.- -generating system, whereas deoxyinosine, deoxyadenosine and benzoate were not. Addition of EDTA to the reaction systems producing radicals greatly enhanced damage to deoxyribose, deoxyinosine, deoxyadenosine and benzoate, but decreased damage to deoxygalactose and deoxyglucose. Further, OH. scavengers were effective inhibitors only when EDTA was present. Inhibition by catalase and desferrioxamine confirmed that H2O2 and iron salts were essential for these reactions. The results suggest that, in the absence of EDTA, iron ions bind to the carbohydrate detector molecules and bring about a site-specific reaction on the molecule. This reaction is poorly inhibited by most OH. scavengers, but is strongly inhibited by scavengers such as mannitol, glucose and thiourea, which can themselves bind iron ions, albeit weakly. In the presence of EDTA, however, iron is removed from these binding sites to produce OH. in 'free' solution. These can be readily intercepted by the addition of OH. scavengers.

Benzoates↗
PubMed2002

Galacto, gluco, manno, and disaccharide-based C-glycosides of 2-amino-2-deoxy sugars.

[reaction: see text] Starting from readily available precursors, selenoglycosides derived from GalNAc, GlcNAc, and ManNAc were prepared by either a one- or a two-step process. The anomeric selenides underwent facile C-Se homolysis to provide the corresponding anomeric radicals, which were trapped with alkenes to give C-glycosides. This provides a general entry to alpha-C-glycosides based on 2-amino-2-deoxy sugars that is also applicable to disaccharide variants.

Amino Sugars↗
PubMed2004

Benzylidene acetal fragmentation route to 6-deoxy sugars: direct reductive cleavage in the presence of ether protecting groups, permitting the efficient, highly stereocontrolled synthesis of beta-D-rhamnosides from D-mannosyl glycosyl donors. Total synthesis of alpha-D-Gal-(1-->3)-alpha-D-Rha-(1-->3)- beta-D-Rha-(1-->4)-beta-D-Glu-OMe, the repeating unit of the antigenic lipopolysaccharide from Escherichia hermannii ATCC 33650 and 33652.

An approach to the stereocontrolled synthesis of beta-d-rhamnopyranosides is described in which 2,3-O-benzyl or related 4,6-O-[alpha-(2-(2-iodophenyl)ethylthiocarbonyl)benzylidene]-mannosyl thioglycosides are first used to introduce the beta-d-mannopyranoside linkage in high yield and stereoselectivity. Following glycosylation, treatment with tributyltin hydride in toluene at reflux brings about reductive radical fragmentation directly to the 6-deoxy sugar in high yield. A variation of these donors bearing a carboxylated donor on O3 is a highly alpha-selective mannosyl and, after radical fragmentation, alpha-d-rhamnosyl donor. Using this stereoselective glycosylation/radical-fragmentation approach, a concise synthesis of the title tetrasaccharide is realized in which both the beta-d- and alpha-d-rhamnopyranosyl units are obtained in a single step by a double radical fragmentation of the modified benzylidene acetals.

Benzylidene Compounds↗