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Treating partially protected sugar hemiacetals with triphosgene in THF results in the formation of glycosyl chlorides. The method is compatible with acid-sensitive isopropylidene protecting groups in the hemiacetal substrates. (C) 2000 Elsevier Science Lt

C-Aryl glycosides are of high value as drug candidates. Here a novel and cost-effective nickel catalyzedortho-CAr-H glycosylation reaction with high regioselectivity and excellent α-selectivity is described. This method shows great functional group compatibility with various glycosides, showing its synthetic potential. Mechanistic studies indicate that C-H activation could be the rate-determining step.

A general method has been developed for the formation of glycosyl chlorides and bromides from picolinic esters under mild and neutral conditions. Benchtop stable picolinic esters are activated by a copper(II) halide species to afford the corresponding products in high yields with a traceless leaving group. Rare β glycosyl chlorides are accessible via this route through neighboring group participation. Additionally, glycosyl chlorides with labile protecting groups previously not easily accessible can be prepared.

The present invention relates to a synthetic saccharide of general formula (I) that is related to Clostridium difficile PS-II cell-surface polysaccharide and conjugate thereof. Said synthetic saccharide, said conjugate and pharmaceutical composition containing said synthetic saccharide or said conjugate are useful for prevention and/or treatment of diseases associated with Clostridium difficile. Furthermore, the synthetic saccharide of general formula (I) is useful as marker in immunological assays for detection of antibodies against Clostridium difficile bacteria.

A straightforward and scalable method for the synthesis of protected 2-hydroxyglycals is described. The approach is based on the chlorination of carbohydrate-derived hemiacetals, followed by an elimination reaction to establish the glycal moiety. 1,2-dehy

The invention discloses a method for preparing halogenated sugar under mild conditions. The method comprises the following steps that an easily-prepared thioglycoside donor and a halogen simple substance or halogen intercompound undergo a reaction at room temperature to obtain the halogenated sugar (chlorine, bromine and iodine). The halogen simple substance or the halogen intercompound is commercial easily available iodine elementary substance, iodine bromide and iodine chloride. The method is suitable for various pyranoses and furanoses. The method has no limitation on a protecting group ofthe thioglycoside donor, and the protecting group can be an electron withdrawing group such as acetyl, benzoyl and the like, and can also be an electron donating group such as benzyl, silicon base andthe like. Meanwhile, the reaction can occur in various organic solvents such as dichloromethane, acetonitrile and methylbenzene. The preparation method of the halogenated sugar is simple, reaction conditions are mild, raw materials are easy to obtain, the application range is wide, the halogenated sugar is compatible with acid-labile groups such as isopropylidene ketal and silicon groups, and a pure product can be obtained by removing a solvent from the halogenated sugar which is not stable in the separation process.

A gold-catalyzed glucosylation method using an o-ethynylphenyl β-D-1-thioglucoside as donor is described. The reaction proceeds in a mostly SN2 pathway. A series of α-D-glucosides are obtained in good yields and with up to 19:1 α-selectivity.

The stereoselective synthesis of glycosyl chlorides using catalytic Appel conditions is described. Good yields of α-glycosyl chlorides were obtained using a range of glycosyl hemiacetals, oxalyl chloride and 5 mol% Ph3PO. For 2-deoxysugars treatment of the corresponding hemiacetals with oxalyl chloride without phosphine oxide catalyst also gave good yields of glycosyl chloride. The method is operationaly simple and the 5 mol% phosphine oxide by-product can be removed easily. Alternatively a one-pot, multi-catalyst glycosylation can be carried out to transform the glycosyl hemiacetal directly to a glycoside.

Stereocontrolled chemical glycosylation remains a major challenge despite vast efforts reported over many decades and so far still mainly relies on trial and error. Now it is shown that the relative reactivity value (RRV) of thioglycosides is an indicator for revealing stereoselectivities according to four types of acceptors. Mechanistic studies show that the reaction is dominated by two distinct intermediates: glycosyl triflates and glycosyl halides from N-halosuccinimide (NXS)/TfOH. The formation of glycosyl halide is highly correlated with the production of α-glycoside. These findings enable glycosylation reactions to be foreseen by using RRVs as an α/β-selectivity indicator and guidelines and rules to be developed for stereocontrolled glycosylation.

Glycosyl chlorides have historically been activated using harsh conditions and/or toxic stoichiometric promoters. More recently, the Ye and the Jacobsen groups showed that glycosyl chlorides can be activated under organocatalytic conditions. However, thos

A general formamide-catalyzed protocol for the efficient transformation of alcohols into alkyl chlorides, which is promoted by substoichiometric amounts (down to 34 mol %) of inexpensive trichlorotriazine (TCT), is introduced. This is the first example of a TCT-mediated dihydroxychlorination of an OH-containing substrate (e.g., alcohols and carboxylic acids) in which all three chlorine atoms of TCT are transferred to the starting material. The consequently enhanced atom economy facilitates a significantly improved waste balance (E-factors down to 4), cost efficiency, and scalability (>50 g). Furthermore, the current procedure is distinguished by high levels of functional-group compatibility and stereoselectivity, as only weakly acidic cyanuric acid is released as exclusive byproduct. Finally, a one-pot protocol for the preparation of amines, azides, ethers, and sulfides enabled the synthesis of the drug rivastigmine with twofold SN2 inversion, which demonstrates the high practical value of the presented method.

A mild and convenient method for the synthesis of α-glycosyl chlorides in high 80–96 % yields within 15–30 min using 2-chloro-1,3-dimethylimidazolinium chloride (DMC) is disclosed. The method has a wide substrate scope and is compatible with labile OH protecting groups, including benzyl, acetyl, benzoyl, isopropylidene, benzylidene, TBDMS (tert-butyldimethylsilyl), and TBDPS (tert-butyldiphenylsilyl) groups. The excellent α selectivity obtained in this reaction is attributed to in-situ isomerization of β-glycosyl chlorides to the more stable α-glycosyl chlorides, as demonstrated by 1H NMR spectroscopic studies. Disarmed sugars with OBz or OAc groups at C-2 were chlorinated at a faster rate but ismomerized (β→α) at a slower rate than armed sugars with an OBn group at C-2. More importantly, the method enables highly desirable one-pot glycosylation reactions to take place, thus allowing efficient syntheses of disaccharides and simple O-glycosylated sugars in high overall yields without the need for separation or purification of the α-glycosyl chloride donors. This method will be especially useful for direct glycosylation reactions using glycosyl chloride donors that are unstable upon separation and purification.

Glycosyl chlorides, useful as glycosyl donors in glycoside synthesis and precursors in organic synthesis, can be easily prepared under solvent-free conditions by exposing a sugar hemiacetal to an equimolar mixture of PPh3 and hexachloroacetone

Gold(III) chloride as catalyst for O-glycosyl trichloroacetimidate activation revealed low affinity to the glycosyl donor but high affinity to the hydroxy group of the acceptor alcohol moiety, thus leading to catalyst-acceptor adduct formation. Charge sep

Base-promoted glycosylation is a recently established stereoselective and regioselective approach for the assembly of di- and oligosaccharides by using partially protected acceptors and glycosyl halide donors. Initial studies were performed on partially methylated acceptor and donor moieties as a model system in order to analyze the key principles of oxyanion reactivities. In this work, extended studies on base-promoted glycosylation are presented by using benzyl protective groups in view of preparative applications. Emphases are placed on the influence of the acceptor anomeric configuration and donor reactivities.

A derivative of diphenylborinic acid promotes catalytic, regioselective Koenigs-Knorr glycosylations of carbohydrate derivatives bearing multiple secondary hydroxyl groups. Robust levels of selectivity for the equatorial OH group of cis-1,2-diol motifs ar

Glycosyl chlorides, with ether or isopropylidene acetal protecting groups, readily available from furanoses or pyranoses, can be conveniently transformed into C-1 alkyl or aryl glycals by reaction with alkyl or aryl organolithium reagents.

A mild and efficient chlorination method for production of glycosyl chlorides is first described which employs inexpensive trichlorotriazine (TCT) and DMF as a chlorination reagent and is compatible with typical acid-labile hydroxyl protecting functions. The scope and limitations, reaction mechanism and its application in the sequential glycosylations are discussed.

A compound having SGLT1 and/or SGLT2 inhibitory activity which is usable as an agent for the prevention or treatment of diabetes, postprandial hyperglycemia, impaired glucose tolerance, diabetic complications, obesity, etc. It is a 1-(β-D-glycopyranosyl)-3-substituted nitrogen-containing heterocyclic compound represented by the general formula (I), a prodrug, or a pharmaceutically acceptable salt thereof, or a hydrate or solvate thereof; an SGLT inhibitor containing the same; a pharmaceutical composition containing the same and a medicinal use thereof. In the formula, ring A represents optionally substituted aryl or heteroaryl; Q1 to Q5 independently represent a carbon atom having a hydrogen atom or substituent bonded thereto or a nitrogen atom; E represents a single bond, alkylene, -O-, -S- or -NH-; and R.represents methyl, ethyl, fluoromethyl or hydroxymethyl.

The stereochemical outcome of glycosylation reactions with model thioglycosides and selenoglycosides proved to be dependent on the source of promoter iodonium ion, with iodine giving different results to N-iodosuccinimide (NIS) alone or N-iodosuccinimide/

The synthesis of a variety of new 1-thio-D-glucopyranose derivatives oxidized at the sulfur atom is described, including seven 1-C-sulfonic acids, three sulfonate esters, three sulfinate esters, an S,S′-diglycosyl thiolsulfonate and thiolsulfmate, four S-

Aldopyranose peracetates react with thionyl chloride and BiCl3, generated in situ from a substoichiometric amount of the procatalyst BiOCl, producing the corresponding peracylated aldopyranosyl chlorides in very good to excellent yields (82-97%

The conversion of 1,1′-thio-linked glucopyranosyl α-D-mannopyranosides to 1,2-thio-linked methyl sophorosides or methyl kojibiosides is described. The method involves the 1→2-migration of the thioglucopyranosyl portion of the nonreducing disaccharide with inversion of configuration at C-2 of the mannopyranose ring and concomitant formation of the methyl glucopyranoside. The thioglucosyl migration does not occur when electron-withdrawing benzoate protecting groups are present. The rearrangement occurs with retention of configuration in the migrating thioglucoside but the methyl glycoside is formed as a mixture of α- and β-isomers. This is attributed to a mechanism involving an oxacarbenium-ion intermediate rather than an episulfonium-ion intermediate. The relevance of this work to recent theoretical predictions concerning the relative stability of such intermediates is discussed.

(equation presented) Because of the vast structural diversity encountered in the field of glycobiology, versatile methods for orthogonal oligosaccharide assembly are always of interest. Reported herein is the preparation of glycosyl chloride donors obtained by reaction of the corresponding thioglycoside precursors with chlorosulfonium chloride reagent 4. The crude chlorides thus obtained can be used directly in subsequent glycosylation reactions, and examples of the generality of this approach are provided.

Glycosyl iodides have been prepared and subjected to glycosylation under neutral conditions. The reactions are highly efficient, giving α glycosides even with sterically demanding glycosyl acceptors. Glucosyl iodides react with allyl alcohol slowest and require refluxing conditions. Galactosyl iodides are intermediate in reactivity, providing the allyl glycoside in 3 h at room temperature, whereas glycosylation of fucosyl iodides occurs in less than 1 h under similar conditions. The scope and limitations of the reactions were demonstrated with a variety of acceptors, including an anomeric hydroxyl group, to give trehalose analogs. β-Selective glycosylation of glucosyl iodides, in the absence of C-2 participation, could be achieved by simply changing the solvent from benzene to acetonitrile. Copyright (C) 1999 Elsevier Science Ltd.

The anodic transformation of 2,3:5,6-di-O-isopropylidene-α-D- mannofuranose (4) and 2,3,4,6-tetra-O-benzyl-D-glucopyranose (5) to the corresponding alkoxy phosphonium ions induces dehydroxy substitution of the sugars at the anomeric positions. Their dehyd

p-Methoxyphenyl (pMP) β-D-glycopyranosides (Glc, Gal, GlcNPhth, GalNPhth, GlcNTroc, Galβ4Glc, Galα4Gal) were prepared from the corresponding 1-O-acetyl sugars in 79-90% yield, using boron trifluoride etherate as promoter. Treatment of the pMP glycosides with acyl chlorides or bromides in the presence of various Lewis acids gave the corresponding glycosyl chlorides and bromides in 81-98% yield. Treatment of the acyl-protected pMP glycosides with thiophenol and boron trifluoride etherate gave the corresponding thioglycosides in 80-100% yield and high (> 20:1) β/α selectivity. The stability of pMP glycosides was investigated against a series of reagents.

Glycosyl chlorides with acid-labile protecting groups were prepared from their corresponding alcohols under basic conditions in good yields. The synthesis of a 1,6-C-linked disaccharide was carried out via reaction of a glycosyl chloride with an aldehyde

The reaction of protected monosaccharides or oligosaccharides or protected monosaccharide and oligosaccharide derivatives containing an anomeric hydroxyl group with secondary α-haloenamines affords high yields of protected glycosyl halides, which are valuable intermediates for the introduction of sugar groups in the synthesis of oligosaccharides, glycolipids or glycopeptides.

The synthesis and conformations of 3-O-methylDMJ, 3-O-(α-D-glucopyranosyl)-DMJ (Glcα1,3DMJ), and 3-O-(α-D-mannopyranosyl)-DMJ (Manα1,3DMJ) are described.Manα1,3DMJ and Glcα1,3DMJ are shown to be very powerful inhibitors of an endomannosidase.The potential

Glycoconjugates of some mycotoxins were prepared by the phase-transfer catalyzed glycosylation procedure. With zearalenone a regio- and stereospecific glucosylation gave the natural derivative which proved to be a 'masked mycotoxin'. In the case of ochrat

The tetrasaccharide a-D-Glcp-(1----4)-a-D-Xylp-(1----4)-a-D-Xylp-(1----4)-D- Glcp (1) has been synthesized, as a substrate analogue of alpha amylase, by silver perchlorate-catalyzed glycosylation of benzyl 2,3,6-tri-O-benzyl-4-O-(2,3-di-O-benzyl-a-D-xylopyranosyl)-beta-D- glucopyranoside (30) with 2,3-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-a-D- glucopyranosyl)-a-D-xylopyranosyl chloride or by methyl triflate-promoted condensation of 30 with methyl 2,3-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-a-D-glucopyranosyl)-1-thio- beta-D-xylopyranoside, followed by removal of protecting groups of the resulting tetrasaccharide derivative 40.

Treatment of a variety of protected 2-(trimethylsilyl)ethyl (SE) mono, di and trisaccaride glycosides and hemiacetal sugars with α,α-dichloromethyl methyl ether (DCMME) in the presence of ZnCl2, SnCl4 or FeCl3 in dichloromethane gave their corresponding 1

The anomeric hydroxyl group of various furanose and pyranose hemiacetals can be replaced by a fluorine, chlorine, bromine or iodine atom under neutral conditions using haloenamines.

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Glycosyl halides which are O-acylated or O-alkylated at least in the 2-position are transhalogenated with alkali metal hydrogen difluorides in a polar-aprotic solvent and, if appropriate, the product is anomerized with the addition of less than the stoichiometric amounts of an inorganic fluoride with a Lewis acid character. Depending on the substrate, the glycosyl fluorides with the 1,2-trans or 1,2-cis configuration are obtained.

Twenty-seven mono --> tetrasaccharidic 2-(trimethylsilyl)ethyl (TMSET) glycosides were synthesized by the Koenigs-Knorr-type method in combination with a wide range of standard reagents for glycoside synthesis and protecting-group chemistry.Variously protected TMSET glycosides were treated with BF3*Et2O (0.7-0.8 equiv) and different carboxylic anhydrides (1.1-15 equiv) in toluene at 22-55 deg C, which gave in one step the corresponding protected 1-O-acyl sugars.In the majority of cases, the yields of purified compounds exceeded 90percent and the anomeric configuration of the starting TMSET glyoside was conserved to a large extent (>95percent) in most of the 1-O-acylated products.Unprotected and acetyl-, benzoyl-, benzyl-, dimethyl-tert-butylsilyl-, and phthaloyl-protected mono-->tetrasaccharidic TMSET glycosides were anomerically deblocked by using trifluoroacetic acid in dichloromethane at 0-22 deg C for 10-30 min.The hemiacetal products were isolated in 88-96percent yield; all reagents and byproducts were volatile and easily removed.

Stereoselective, total synthesis of O-alpha-D-galactopyranosyl-(1----4) -O-beta-D-galactopyranosyl-(1----4)-O-beta-D-glucopyranosyl-(1----1)-N -tetracosanoyl-[2S,3R,4E (and 4Z)]-sphingenine and O-alpha-D -galactopyranosyl-(1----3)-O-beta-D-galactopyranosyl-(1----4)-O-beta-D -glucopyranosyl-(1----1)-N-tetracosanoyl-(2S,3R,4E)-sphin gen ine was achieved by using O-(2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl) -(1----4)-O-(2,3,6-tri-O-acetyl-beta-D-galactopyranosyl)-(1----4)-2,3,6- tri-O-acetyl-alpha-D-glucopyranosyl trichloroacetimidate, O-(2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl) -(1----4)-O-(2,3,6-tri-O-acetyl-beta-D-galactopyranosyl)-(1----4)-2,3,6- tri-O-acetyl-alpha (and beta)-D-glucopyranosyl fluoride, and O-(2,3,4,6-tetra-O-acetyl-alpha-D -galactopyranosyl)-(1----3)-O-(2,3,6-tri-O-acetyl-beta-D-galactopyran osyl)-(1----4)-2,3,6-tri-O-acetyl-alpha-D-glucopyranosyl trichloroacetimidate.

The stereoselective synthesis of the 1-O-α-D-glucopyranosides and 1-O-α-D-cellobiosides of 3-deoxy-2(R)- and 2(S)-glycerols to determine the complete stereochemistry of rhynchosporoside, which is a host selective phytotoxin from Rhynchosporium secalis, is

The glycosyl trichloroacetimidates 1-α,β, 8-α, 11-α, 13-α, 15-α, and 17-α directly transfer the glycosyl moiety to phosphoric acid mono- and diesters.The acidity of the phosphoric acid derivatives used was sufficient for the activation of the trichloroacetimidates, therefore an additional acidic catalyst was not required.From the β-imidate 1-β α-glycosyl phosphate and from the α-imidates preferentially β-glycosyl phosphates were obtained.Reaction of dibenzyl phosphate (2a) and cetyl phosphate (2c) with 1-α demonstrated that β/α-anomerization iscatalyzed by traces of acid.The glycosyl phosphates 3a-α, 3a-β - 3c-β, 3f-α, 9a-β, and 9c-β were partly or totally deprotected.The structures of the synthezised compounds were assigned by 1H NMR spectroscopy and by comparison with literature data.

The synthesis of 2-O-α-D-galactopyranosyl-D-galactopyranose was accomplished by condensation of 2,3,4,6-tetra-O-benzyl-α-D-galactopyranosyl chloride with 2,2,2-trichloroethyl 3,4,6-tri-O-benzyl-α-D-galactopyranoside in the presence of mercuric cyanide.The

Stereoselective α-glucosylation of partially protected carbohydrates with 2,3,4,6-tetra-O-benzyl-α-D-glucopyranose in dichloromethane, in the presence of a quaternary mixture of 4-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, N,N-dimethylacetamide, and triethylamine gave O-α-D-glucopyranosyl-(1->4)- and -(1->6)-2-acetamido-2-deoxy-D-glucopyranose (N-acetylmaltosamine and N-acetylisomaltosamine).A step-by-step synthesis of O-α-D-glucopyranosyl-(1->4)-O-6)>-D-glucopyranose is described.

The treatment of aldose derivatives that are protected at all but the anomeric hydroxy groups with N-dichloromethylene-N,N-dialkylammonium chlorides (alkyl = Me, Et) provides an improved method of preparing the corresponding glycosyl chlorides.Analogous derivatives containing an unprotected C1-C2 diol give 2-O-(N,N-dialkylcarbamoyl)glycosyl chlorides.

The disaccharide glycoside 8-methoxycarbonyloctyl 4,6-O-cyclohexylidine-2-O-(tetra-O-benzyl-alpha-D-galactopyranosyl)-alpha-D-manno pyranoside (7) was used as a common intermediate to the trisaccharide determinants of both Salmonella serogroups A and D1.

Silver imidazolate together with mercury(II) chloride in dichloromethane is an efficient promoting system for glycosidations using the stable 2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl and α-D-galactopyranosyl chlorides.This glycosidation promotor is usefu

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