Unprotected Sugars Research Articles

Direct azidation of unprotected carbohydrates under Mitsunobu conditions using hydrazoic acid

A single step procedure for the direct and regioselective synthesis of carbohydrate azides from unprotected sugars using hydrazoic acid under Mitsunobu conditions is reported. A series of mono-, di-, or triazido polyhydroxylated systems are described.

Iron(III) Chloride in Ethanol-Water: Highly Efficient Catalytic System for the Synthesis of Garcia Gonzalez Polyhydroxyalkyl- and C-Glycosylfurans

An efficient method has been developed for the synthesis of Garcia Gonzalez polyhydroxyalkyl- and C-glycosylfurans in excellent yields from unprotected sugar aldoses with β-keto esters by Knoevenagel condensation in the presence of anhydrous iron(III) chloride.

Direct Transformation of Unprotected Sugars to Aryl 1-Thio-β-glycosides in Aqueous Media Using 2-Chloro-1,3-dimethylimidazolinium Chloride

Abstract Aryl 1-thioglycosides have directly been synthesized in good yields from the corresponding unprotected sugars and thiols without protection of the hydroxy groups by using 2-chloro-1,3-dimethylimidazolinium chloride (DMC) as dehydrative condensing agent. The reaction proceeded in a mixed solvent of water and acetonitrile under mild reaction conditions, leading to the predominant formation of β-anomers.

First phosphorous d-xylose-derived glycodendrimers

Phosphorous glycodendrimers have been prepared in quantitative yields by grafting xylose-derived moieties on phosphorous dendrimers involving hydrazone units. These dendrimers could be hydrophobic or amphiphilic, respectively, with acetylated or unprotected sugar moieties.

Green glycosylation using ionic liquid to prepare alkyl glycosides for studying carbohydrate–protein interactions by SPR

Several simple glycosides of D-glucose (Glc) and N-acetyl-D-galactosamine (GalNAc) were prepared in a single step glycosylation reaction using unprotected and unactivated sugar donors. The resulting GalNAc glycoside, containing a bifunctional linker, was used to immobilize this glycoconjugate to a self assembled monolayer on a gold biosensor chip. Surface plasmon resonance (SPR) experiments demonstrated that this immobilized glycoconjugate bound to GalNAc specific lectin, Viscum album agglutinin.

One-step conversion of unprotected sugars to β-glycosyl azides using 2-chloroimidazolinium salt in aqueous solution

Various beta-glycosyl azides have been synthesized directly in water by the reaction of unprotected sugars and sodium azide mediated by 2-chloro-1,3-dimethylimidazolinium chloride (DMC).

Aryl C‐Glycosylation Using an Ionic Liquid Containing a Protic Acid.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Oxidative Removal of Heterocyclic Alkyl or Sugar Side Chain by Microwave: A Simple Step to Xanthopterin, 6-Formylpterin, and 3-Hydroxymethyl-2(1H)-quinoxalinone

Abstract One-step microwave-assisted oxidative removal of 3-methyl and 3-sugar side chain in 2(1H)-quinoxalinone system by selenium dioxide and sodium periodate respectively resulting 2(1H)-quinoxalinone has been reported. Similarly xanthopterin (as acetyl derivative 11) was isolated from selenium dioxide oxidation of 7-methylxanthopterin. In the absence of adjacent lactam moiety, sodium periodate efficiently oxidizes 2-acetylaminopterin tetrols 7 and 8 to 2-acetylamino-6-formylpterin (16) and the quinoxaline tetrols 9 and 10 respectively to quinoxaline aldehyde 17. However, all the compounds remained unchanged on refluxing with selenium dioxide. The new quinoxalone compounds 15 and 18 were simply synthesized by manganese dioxide oxidation of the completely unprotected 3-substituted sugar of 2(1H)-quinoxalinone 5 and quinoxaline 10 respectively under microwave condition.

Aryl C-glycosylation using an ionic liquid containing a protic acid

Aryl C-glycosylation of several glycosyl donors, including unprotected sugars, with phenol and naphthol derivatives in an ionic liquid containing a protic acid proceeded effectively and stereoselectively to give the corresponding aryl C-glycosides in good to high yields. Because the ionic liquid was nonvolatile, the reaction could be carried out under reduced pressure; in addition, the ionic liquid could be reused without loss of effectiveness. These features contribute to the significant advantages of this novel aryl C-glycosylation reaction.

Preparation of New Perfluoroalkylated Carbamate Group-containing Glycoside-based Nonionic Surfactants

Abstract The present work describes the synthesis of new perfluoroalkylated carbamate group-containing glycoside-based nonionic surfactants usable as co-surfactants for stabilizing injectable oxygen-carriers PFC emulsions and as potential antithrombotic agents. The key steps of the synthetic route converting F-alkyl oxoesters into new F-alkyl glycosides are: formolysis, conversion to the respective acid chloride, isocyanate formation and glycosidation. The perfluoroalkyl group is connected through a carbamate function to 6-position of the sugar ring, and the glycosidation is performed from unprotected sugar.

Scandium cation-exchanged montmorillonite catalyzed direct C-glycosylation of a 1,3-diketone, dimedone, with unprotected sugars in aqueous solution

The condensation of dimedone with unprotected sugars in aqueous solution in the presence of a catalytic amount of Sc 3+-montmorillonite (Sc 3+-mont) gave 9-hydroxyalkyl-3,3,6,6,-tetramethyl-3,4,5,6,7,9-hexahydro-1 H-xanthene-1,8(2 H)-diones in good yields, while the use of Sc(OTf) 3 instead of Sc 3+-mont gave the hydroxyalkyl-6,7-dihydrobenzofuran-4(5 H)-one derivatives in good yields. Furthermore, Sc 3+-mont could be recycled without inactivation.

A Generalized Procedure for the One‐Pot Preparation of Glycosyl Azides and Thioglycosides Directly from Unprotected Reducing Sugars under Phase‐Transfer Reaction Conditions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Novel glycosylation methods and their application to natural products synthesis

In this short review article, several glycosylation methods that were developed in our laboratories, including stereocontrolled glycosylation using 2,6-anhydro-2,6-dideoxy-2,6-dithio sugars for obtaining 2,6-dideoxy glycosides, C-glycosylation employing unprotected sugars, environmentally benign glycosylation utilizing heterogeneous solid acids and ionic liquids, are recounted. In addition, representative and significant applications of these methods to the synthesis of complex natural products are described.

A Generalized Procedure for the One‐Pot Preparation of Glycosyl Azides and Thioglycosides Directly from Unprotected Reducing Sugars under Phase‐Transfer Reaction Conditions

AbstractPer‐O‐acetylated glycosyl azides and thioglycosides were prepared in excellent yield directly from unprotected reducing sugars through in situ generation of per‐O‐acetylated glycosyl bromides by a generalized one‐pot procedure under phase‐transfer conditions. Stereoselective products were formed with complete inversion at the anomeric centers of the glycosyl bromides to provide a general high‐yielding procedure for the preparation of 1,2‐trans‐glycosyl azides and thioglycosides.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

C‐Glycosidation Using Unprotected Sugars and Synthesis of C‐Glycoside Antibiotics

AbstractFor Abstract see ChemInform Abstract in Full Text.

Modified One‐Pot Protocol for the Preparation of Thioglycosides from Unprotected Aldoses via S‐Glycosyl Isothiouronium Salts*

An efficient one‐pot protocol for the direct preparation of thioglycosides starting from unprotected reducing sugars via S‐glycosyl isothiouronium salts is reported. In this one‐pot methodology, BF3 · OEt2 has been used as a general catalyst for both per‐O‐acetylation of sugars and conversion of sugar per‐O‐acetates into S‐glycosyl isothiouronium salts, which was allowed to react with alkylating agents in the presence of a base to furnish thioglycosides in excellent yield. *C.D.R.I. communication no. 6767. Authors contributed equally to this work.

New Carbohydrate Derivatives of Norfloxacin.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Single-Step Method for the Production of Sugar Hydrazides: Intermediates for the Chemoselective Preparation of Glycoconjugates

The ability to selectively conjugate carbohydrate molecules to a protein is a key step in the preparation of conjugate vaccines, while facile methods for linking carbohydrates to polymers or solid surfaces to produce diagnostic probes and functional microarrays are also sought. Here, we describe a simple, single-step method of producing glycosylhydrazides from unprotected sugars, which were then linked in a controlled manner to a desired carrier, through an appropriate linker. The method was chemoselective and did not require coupling reagents, and the native pyranose form of the reducing end residue was retained. Initially, mono- and disaccharide hydrazides were produced from the corresponding reducing sugars and linked to BSA through a bifunctional linker. Final exemplification of the procedure was demonstrated by the preparation of a LewisY tetrasaccharide protein conjugate, which was recognized by a LewisY monoclonal antibody indicating the preservation of the natural conformation of the tetrasaccharide in the final construct. It is envisaged that this method will have general applicability to a variety of functionally diverse reducing sugars and provide a route to highly defined glycoconjugates, without the need for elaborate synthetic strategies.

One-pot synthesis of per- O-acetylated thioglycosides from unprotected reducing sugars

A sequential per- O-acetylation and thioglycosidation of unprotected reducing sugars using a stoichiometric quantity of acetic anhydride and alkyl- or arylthiols is reported. These reactions, which are catalyzed by BF 3·OEt 2, together constitute an efficient one-pot method for the synthesis of acetylated thioglycosides.

Iodine: A Versatile Reagent in Carbohydrate Chemistry. Part 16. Streamlined Synthesis of Per‐O‐acetylated Sugars, Glycosyl Iodides, or Thioglycosides from Unprotected Reducing Sugars.

AbstractFor Abstract see ChemInform Abstract in Full Text.