Unprotected Carbohydrates Research Articles

Base-modified nucleosides from carbohydrate derived oxazolidinethiones: a five-step process

Starting from unprotected carbohydrates, base-modified nucleosides could be reached in four steps through the condensation of anthranilic acid with a suitably protected sugar-derived 2-alkylthio-1,3-oxazoline.

CHEMOENZYMATIC SYNTHESIS OF SURFACTANTS FROM CARBOHYDRATES, AMINO ACIDS, AND FATTY ACIDS

The chemoenzymatic synthesis of new surfactants is reported; they were prepared from unprotected carbohydrates, amino acids, and fatty acids. This study pointed out the factors that govern the possibility to enzymatically bind the carbohydrate to the amino acid.

Ready protease-catalyzed synthesis of carbohydrate–amino acid conjugates

The protease-catalyzed synthesis of amino acid est-carbohydrate conjugates as glycopeptide analogues has been achieved in a highly regioselective and carbohydrate-specific manner using amino acid vinyl ester acyl donors and minimally or completely unprotected carbohydrate acyl acceptors, which together probed active sites of proteases to reveal yield efficiencies that are modulated by the carbohydrate C-2 substitutent, and that may be exploited to allow selective one-pot syntheses.

One-step synthesis of biotinyl photoprobes from unprotected carbohydrates

A simple and versatile approach for the preparation of carbohydrate photoprobes has been developed. By a single-step reaction at 37 degrees C, a biotinylated carbene-generating unit was introduced to the reducing end of unprotected carbohydrates. Micromole quantities of N-acetyllactosamine, Lewis X trisaccharide, and sialyl Lewis X tetrasaccharide were easily converted to their biotinylated photoreactive analogues, which enabled the nonradioisotopic chemiluminescent detection of the photolabeled products. Thus, a sequence of lectin photoaffinity labeling, from the probe synthesis to the detection of labeled protein, was readily accomplished within one week. Our strategy may be applicable to any aldehyde-bearing ligand.

Short synthetic glycopeptides successfully induce antibody responses to carcinoma‐associated Tn antigen

Glycopeptides containing a tumor-associated carbohydrate antigen (mono-, tri- or hexa-Tn antigen) as a B-cell epitope and a CD4+ T-cell epitope (PV: poliovirus or TT: tetanus toxin) were prepared for immunological studies. Several Tn antigen residues [FmocSer/Thr (alpha-GalNAc)-OH] were successively incorporated into the peptide sequence with unprotected carbohydrate groups. The tri- and hexa-Tn glycopeptides were recognized by MLS128, a Tn-specific monoclonal antibody. The position of the tri-Tn motif in the peptide sequence and the peptide backbone itself do not alter its antigenicity. As demonstrated by both ELISA and FACS analysis, the glycopeptides induced high titers of anti-Tn antibodies in mice, in the absence of a carrier molecule. In addition, the generated antibodies recognized the native Tn antigen on cancer cells. The antibody response obtained with a D-(Tn3)-PV glycopeptide containing three alpha-GalNAc-D-serine residues is similar that obtained with the Tn6-PV glycopeptide. These results demonstrate that short synthetic glycopeptides are able to induce anticancer antibody responses.

Chemo-Enzymatic Synthesis of New Non Ionic Surfactants from Unprotected Carbohydrates

ABSTRACT The synthesis of new non ionic surfactants is reported. They were prepared from unprotected carbohydrates, amino acids, and fatty alcohols. These modules were linked by enzymatic esterification and transesterification reactions catalysed by lipases and proteases in organic media.

ChemInform Abstract: Selective Phosphitylation of the Primary Hydroxyl Group in Unprotected Carbohydrates and Nucleosides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Selective phosphitylation of the primary hydroxyl group in unprotected carbohydrates and nucleosides.

[reaction: see text] Carbohydrates and nucleosides containing a phosphate at the less-hindered primary hydroxyl group are often prepared using a protection/deprotection strategy. Herein we report that the phosphoramidite method can be used to selectively incorporate phosphorus at the primary hydroxyl group of O-unprotected carbohydrates and nucleosides; in situ oxidation of the resulting phosphite triester yields the phosphate triester.

Ozonolytic depolymerization of polysaccharides in aqueous solution

The selective oxidation of β- d-glycosidic linkages of polysaccharides by ozone has great utility as a general method for depolymerization of polysaccharides. Here we describe a ‘one-step’ method whereby polysaccharides dissolved in water or basic solutions are depolymerized by ozonolysis. The oxidation of glycosidic linkages of unprotected carbohydrates by ozone is complicated by several side reactions. We describe here optimized conditions for carrying out ozonolysis degradation. We also characterize the major pathways for unwanted degradation by various side reactions. In the preferred oxidation pathway, the aldosidic linkage is oxidized to an aldonic ester function that hydrolyzes under the basic conditions employed to give a free aldonate, with cleavage of the polysaccharide chain. Nonselective degradation pathways include oxidative degradation by radical species that oxidize glycosyl residues to formic, acetic, and oxalic acids. The nonselective degradation caused by acids is minimized by basic buffers. The products of polysaccharide depolymerization form a size distribution around a nominal molecular weight, and the average molecular weight of the products can be controlled by the rate or amount of ozone passed through the reaction mixture. The ozonolysis method described herein provides a convenient, inexpensive, and controllable means for generating small polysaccharides or large oligosaccharide fragments.

ビスマスやスズ化合物を用いる有機合成 含水溶媒中や水中での有機合成反応を中心として

This article presents organic synthesis by using bismuth and tin compounds, especially synthetic organic reaction in aqueous media : (1) A Grignard-type addition of allyl unit to carbonyl compounds containing a carboxyl group by using bismuth trichloride-metallic zinc-allyl bromide. (2) Allylation of aldehydes by using allylic alcohols in the presence of metallic bismuth. (3) A novel aqueous BarbierGrignard-type allylation of aldehydes in a metallic magnesium/bismuth trichloride bimetal system. (4) Allylation of carbonyl compounds by using allyl Grignard reagent and various metallic salts in aqueous media. (5) Allylation of aldehydes by using allyltin compounds in aqueous media. (6) Asymmetric allylation of carbonyl compounds by using tetraallyltin. (7) Bismuth mediated allylation of unprotected carbohydrates. (8) Ether synthesis by using a catalytic amount of bismuth trichloride and triethylsilane. (9) Asymmetric cyanation of aldehydes promoted by a catalytic amount of chiral bismuth compound. (10) Reduction of aldehydes by using tributyltin hydride in methanol or water.

A convenient synthesis of alkyl d-glycofuranosiduronic acids and alkyl d-glycofuranosides from unprotected carbohydrates

O-Glycosylation of a variety of long chain alcohols with totally unprotected uronic acids ( d-glucuronic and d-galacturonic acids) and neutral carbohydrates ( d-glucose, d-galactose, d-mannose and d-glucofuranurono-6,3-lactone), performed in heterogeneous media and promoted by Lewis acids (ferric chloride or boron trifluoride diethyl etherate), afforded alkyl d-glycofuranosiduronic acids and alkyl d-glycofuranosides, respectively, in high yields. Both chemoselectivity and anomeric stereoselectivity were enhanced by complexing agents, i.e. calcium or barium chloride.

SYNTHESIS OF DITHIO-, THIO-AND CARBAMOYL ESTER DERIVATIVES OF MONOSACCHARIDES AND ITOLS

Regiospecific carbamoylation of O-isopropylidene protected monosaccharides and itols gave a large range of novel carbamoyl, thiocarbamoyl and dithiocarbamoyl esters. These fully, partially and unprotected carbohydrates possess both modulable hydrophilic character and potential biological properties. Some carbamoyl esters showed, by NMR spectroscopy, characteristics of Z-E isomerism; the rotational energy barrier was higher for the thiocarbamates than for the corresponding carbamates.

Synthesis of Carbohydrate-Containing Dendrimers. 5. Preparation of Dendrimers Using Unprotected Carbohydrates

Carbohydrate-containing dendrimers have been prepared using completely unprotected carbohydrates employing a convergent growth approach. The facile syntheses of lower generation dendrimers, using the amide bond forming methodology, opens up the possibility of obtaining densely-packed glycodendrimers without the need to resort to protecting group manipulations on the saccharide residues. © 1997 Elsevier Science Ltd.

Manipulation of free carbohydrates via stannylene acetals. Preparation of β-per- O-acyl derivatives of d-mannose, l-rhamnose, [formula omitted], and d-lyxose

A simple and high-yielding method for the preparation of 1- O- β-acyl derivatives of carbohydrates with an axial OH group at C-2 is described. It utilizes the property of unprotected carbohydrates to preferentially form 1,2- O- cis stannylene acetals, when treated with dibutyltin oxide. These acetals can be acylated with retention of configuration at the anomeric position.

ChemInform Abstract: Wittig Chain Extension of Unprotected Carbohydrates: Formation of Carbohydrate‐Derived α,β‐Unsaturated Esters.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Wittig chain extension of unprotected carbohydrates: formation of carbohydrate-derived α,β-unsaturated esters

Unprotected carbohydrates react with Wittig reagents 6 and 7 to give unsaturated esters. This homologation has been used to prepare an intermediate ( 18) previously employed in a synthesis of Kdo ( 19).

An Efficient Synthesis of N-Allylglycosylamides from Unprotected Carbohydrates

Synthetic, multivalent, carbohydrate assemblies are important tools in studying the avidity of many naturally occuring lectins for their ligands. This report details a simple, high-yielding three-step procedure to convert unprotected carbohydrates into N-allylglycosides. This method compliments the reductive amination procedure but allows the reducing-end pyranose ring to remain intact. No carbohydrate protecting groups are needed, and the resulting N-allylglycosylamide can be easily linked to other molecules. Two examples of analogs of silyl Lewisx and sulfo Lewisx have been derivatized by this process.

Synthesis of a Phosphonate Analog of Sialic Acid (Neu5Ac) Using Indium-Mediated Allylation of Unprotected Carbohydrates in Aqueous Media

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTSynthesis of a Phosphonate Analog of Sialic Acid (Neu5Ac) Using Indium-Mediated Allylation of Unprotected Carbohydrates in Aqueous MediaJinming Gao, Valeri Martichonok, and George M. WhitesidesView Author Information Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138 Cite this: J. Org. Chem. 1996, 61, 26, 9538–9540Publication Date (Web):December 27, 1996Publication History Received1 October 1996Published online27 December 1996Published inissue 1 January 1996https://doi.org/10.1021/jo961290yCopyright © 1996 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views437Altmetric-Citations39LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (91 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Indium,Mixtures,Organic compounds,Organic reactions,Organophosphorus compounds Get e-Alerts

Tri- O-acyl 2-deoxy-D-ribofuranose: An effective enzyme-assisted one-pot synthesis from 2-deoxy-D-ribose and transformation into 2′-deoxynucleosides

Regioselective lipase-catalyzed (Novozym 435 ® from Candida antartica) acylations of unprotected 2-deoxy-D-ribose and D-ribose, by use of propionic anhydride, afforded the novel 5- O-monoacylated derivatives 1 and 4, respectively. Subsequent addition of acetic anhydride and pyridine into the reaction mixtures gave the corresponding per- O-acylated pentofuranoses 2 and 5 in almost quantitative overall yields from the unprotected carbohydrates. The versatility of compound 2 as an universal synthon for synthesis of anomeric mixtures of 2′-deoxynucleosides is demonstrated.

A new and direct access to glycono-1,4-lactones from glycopyranoses by regioselective oxidation and subsequent ring restriction

Treatment of partially protected or unprotected carbohydrates with the RhH(PPh 3) 4-benzalacetone system leads exclusively to glycono-1,4-lactones by regioselective oxidation and subsequent ring restriction.