1-hydroxy Sugars Research Articles

Surfactant-mediated thioglycosylation of 1-hydroxy sugars in water.

Thioglycosides are an important class of sugars, since they can be used as non-ionic biosurfactants, biomimetic glycosides, and building blocks for carbohydrate synthesis. Previously, Brønsted- or Lewis-acid-catalyzed dehydrative glycosylations between a 1-hydroxy sugar and a thiol have been reported to yield open-chain dithioacetal sugars as the major products instead of the desired thioglycosides. These dithioacetal sugars are by-products derived from the endocyclic bond cleavage of the thioglycosides. Herein, we report dehydrative glycosylation in water mediated by a Brønsted acid-surfactant combined catalyst (BASC). Glycosylations between 1-hydroxy furanosyl/pyranosyl sugars and primary, secondary, and tertiary aliphatic/aromatic thiols in the presence of dodecyl benzenesulfonic acid (DBSA) provided the thioglycoside products in moderate to good yields. Microwave irradiation led to improvements in the yields and a shortening of the reaction time. Remarkably, open-chain dithioacetal sugars were not detected in the DBSA-mediated glycosylations in water. This method is a simple, convenient, and rapid approach to produce a library of thioglycosides without the requirement of anhydrous conditions. Moreover, this work also provides an excellent example of complementary reactivity profiles of glycosylation in organic solvents and water.

A recyclable heavy fluorous tag carrying an allyl alcohol pendant group: design and evaluation toward applications in synthetic carbohydrate chemistry

Toward applications in synthetic carbohydrate chemistry, we converted our previous acid-resistant heavy fluorous tag [(Rf)3C–CH2–OH, 1] to allyl alcohol derivatives [(Rf)3C–CH2–O–(CH2)n–CHCH–CH2–OH, 3 (n=1) or 4 (n=3)] by means of olefin cross metathesis. They were then subjected to β-glycosylation reactions by using a series of glycosyl donors, including glycosyl bromide and trichloroacetimidates. The terminal OH group in 3 and 4 was found to be β-glycosylated in moderate yield when 2,3,4,6-tetra-O-benzoyl-d-galactosyl trichloroacetimidate was used as the glycosyl donor. Upon a detachment reaction using Pd(PPh3)4, the initial heavy fluorous tag 1 was recovered in high yield (>90%) together with 1-hydroxy sugar, indicating that not only the allyl ether linkage in the glycosides but also the internal di-alkyl ether linkage in 4 be cleaved by the action of the Pd-catalyst enabling long-range olefin transmigration. Potential utility was demonstrated by using the tetra-O-benzoyl-β-d-galactosylated derivative of 3 in a series of deprotection, protection and glycosylation reactions, which were conductible in high yields without using chromatographic purification process. These findings prompt us to propose a general scheme in which the acid-resistant heavy fluorous compound 1 is applied as a recyclable tag in synthetic carbohydrate chemistry.

Sequential one-pot glycosylation with glycosyl N-trichloroacetylcarbamate and trichloroacetate including dehydrative approach using 1-hydroxy sugars

An efficient sequential one-pot glycosylation has been developed with glycosyl trichlorocarbamate and trichloroacetate activated by the same Lewis acid and enabled by a change in reaction temperature. The αα-selective glycosylation was achieved using glucose, galactose, and mannose substrates after investigation into the reactivities of the two types of glycosyl donors. Sequential one-pot dehydrative glycosylation, including in situ preparation of glycosyl donors followed by generation of two glycosyl bonds, provided three types of trisaccharide.

A novel glycosylation of inactive glycosyl donors using an ionic liquid containing a protic acid under reduced pressure conditions

The glycosylation of inactive glycosyl donors, such as methyl glycosides and 1-hydroxy sugars with nearly stoichiometric amounts of various alcohols (1.1 equiv) in an ionic liquid containing a protic acid (acid-IL) under reduced pressure conditions proceeded effectively to give the corresponding glycosides in good to high yields. Furthermore, the acid-IL could be reused for additional glycosylations without the loss of efficiency.

ChemInform Abstract: Diphosphonium Salts as Effective Reagents for Stereoselective Synthesis of 1,2-cis-Ribofuranosides.

1,2-cis-Ribofuranosides are stereoselectively synthesized in high yields directly from 1-hydroxy sugars and alcohols or trimethylsilylated nucleophiles by the use of diphosphonium salts as a condensation reagent.

Improved catalytic and stereoselective glycosylation with glycosyl N-trichloroacetylcarbamate: application to various 1-hydroxy sugars

Efficient catalytic and stereoselective glycosylation was achieved by activating a glycosyl N-trichloroacetylcarbamate with a catalytic amount of Lewis acid in the presence of a glycosyl acceptor and 5 Ǻ molecular sieves. Catalytic one-pot dehydrative glycosylation of a 1-hydroxy carbohydrate was achieved stereoselectively by reaction with trichloroacetyl isocyanate, followed by activation with a catalytic amount of activators.

Formation of O-Glycosidic Linkages from 1-Hydroxy Sugars by Bismuth(III) Triflate-Catalyzed Dehydrative Glycosidation

This paper describes the direct formation of various O-glycosidic linkages from 1-hydroxy sugars by bismuth(III) triflate-catalyzed dehydrative glycosidation. The condensation reactions of 1 -hydroxy sugars with some primary alcohols in the presence of only 5 mol% bismuth(III) triflate at reflux temperature for 15 min in dichloromethane afforded O-glycosides in good yields. An 1,6-anhydro-β-D-glucopyranosidic linkage was formed by the intramolecular condensation of the corresponding 1-hydroxy sugar performed with similar reaction conditions using 5 mol% bismuth(III) triflate. A reaction using 10 mol% bismuth(III) triflate at room temperature in dichloromethane promoted the self- or cross-condensations of 1-hydroxy sugars to produce several kinds of 1,1'-disaccharides. This paper reports some important properties of bismuth(III) triflate catalyzed dehydrative glycosidation using 1-hydroxy sugars to form various O-glycosidic linkages.

Tandem Catalysis Strategy for Direct Glycosylation of 1-Hydroxy Sugars. Methoxyacetic Acid as an Effective Catalytic Mediator

1-Hydroxy sugars were dehydratively coupled with a variety of alcohols including thiophenol in the presence of a catalytic amount of ytterbium(III) triflate [Yb(OTf) 3 ] and methoxyacetic acid to give the corresponding glycosides in good to excellent yields, and in some cases, with high stereoselectivities. The reaction proceeds through selective esterification of 1-hydroxy sugars with methoxyacetic acid in the presence of free alcohols as glycosyl acceptors. The mechanism of methoxyacetic acid-mediated tandem catalysis with Yb(OTf) 3 is discussed.

Surfactant-Type Brønsted Acid Catalyzed Dehydrative Nucleophilic Substitutions of Alcohols in Water

A protocol for the dehydrative nucleophilic substitution of benzyl alcohols with a variety of carbon- and heteroatom-centered nucleophiles using dodecylbenzenesulfonic acid (DBSA) as a surfactant-type Brønsted acid catalyst in water has been developed. The reaction system can be applied to the stereoselective C-glycosylation of 1-hydroxy sugars in water. [reaction: see text].

Dehydrative Glycosylation in Water Using a Brønsted Acid–Surfactant-Combined Catalyst

Abstract Brønsted acid–surfactant-combined catalyst, dodecylbenzenesulfonic acid (DBSA), was used in catalytic dehydrative glycosylation reactions in water. 1-Hydroxy sugars, such as O-benzyl-protected furanose and pyranose, reacted with alcohols and a nitrogen nucleophile in the presence of a catalytic amount of DBSA to afford the desired adducts in good yields. Detailed study of the glycosylation of 2-deoxy-d-ribofuranose showed that hydrophobicity of the substrates was important to attain higher yields. Regarding the α/β selectivities, d-ribose and d-mannose derivatives gave the products in high β- and α-selectivities, respectively.

Glycosyl trichloroacetylcarbamate: a new glycosyl donor for O-glycosylation

Glycosyl trichloroacetylcarbamates, readily obtained by reacting 1-hydroxy sugars with trichloroacetylisocyanate, have been found as excellent glycosyl donors, and the corresponding O-glycosides are formed in good to excellent yields with a fairly good degree of selectivity.

One-pot α-glycosylation pathway via the generation in situ of α-glycopyranosyl imidates in N, N-dimethylformamide

Divergent pathways are disclosed in the activation of 2- O-benzyl-1-hydroxy sugars by a reagent combination of CBr 4 and Ph 3P, all of which afford one-pot α-glycosylation methods. When this reagent is used in CH 2Cl 2, the 1-hydroxy sugar is converted to the α-glycosyl bromide in a conventional way and leads to the one-pot α-glycosylation method based on a halide ion-catalytic mechanism. In either DMF or a mixture of DMF and CHCl 3, however, alternative α-glycosyl species are generated. From the 1H and 13C NMR study of the products, as well as the reactions using Vilsmeier reagents [(CH 3) 2N + CHX]X − (X = Br and Cl), these were identified as cationic α-glycopyranosyl imidates having either Br − or Cl − counter ion. The cationic α-glycosyl imidate (Br −), derived specifically in the presence of DMF, is more reactive than the α-glycosyl bromide and thus is responsible for the accelerated one-pot α-glycosylation. The one-pot α-glycosylation methodology performed in DMF was assessed also with different types of acceptor substrates including tertiary alcohols and an anomeric mixture of 1-OH sugars.

Glycosylation with Glycosyl Benzyl Phthalates as a New Type of Glycosyl Donor.

A glucopyranosyl benzyl phthalate, two mannopyranosyl benzyl phthalates, and a 2-deoxyglucopyranosyl benzyl phthalate, which were prepared from the corresponding 1-hydroxy sugars and benzyl hydrogen phthalate, were found to be efficient glycosyl donors in the glycosylations of various glycosyl acceptors using TMSOTf as a promoter.

Chloramine-T-mediated chemoselective hydrolysis of thioglycosides into glycosyl hemiacetals under neutral conditions

A metal-free, mild, efficient and chemoselective hydrolysis of several thioalkylglycosides ( 1 ) into their corresponding 1-hydroxy sugars ( 2 ) using sodium N-chloro- p-toluenesulfonamide trihydrate (chloramine-T) without affecting other functional groups is reported.

Glycosylation with glycosyl benzyl phthalates as a new type of glycosyl donor.

A glucopyranosyl benzyl phthalate, two mannopyranosyl benzyl phthalates, and a 2-deoxyglucopyranosyl benzyl phthalate, which were prepared from the corresponding 1-hydroxy sugars and benzyl hydrogen phthalate, were found to be efficient glycosyl donors in the glycosylations of various glycosyl acceptors using TMSOTf as a promoter.

Catalytic Glycosylation with Rhodium(III)‐Triphos Catalysts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Catalytic Glycosylation with Rhodium(III)-Triphos Catalysts

The formation of glycosides in high yield from 1-hydroxy sugars using catalytic amounts (0.5mol%) of Rh(III)Cl3(triphos) (1a) or [Rh(III)(MeCN)3(triphos)](TfO)3 (1b) is described. High stereocontrol at the anomeric center is achieved by neighboring group participation. In addition, an application of this new glycosylation procedure for the synthesis of a derivative of the oviposition-deterring pheromone of the cherry fruit fly Rhagoletis cerasi is presented.

Reducing Oligosaccharides via Glycal Assembly: On the Remarkable Stability of Anomeric Hydroxyl Groups to Global Deprotection with Sodium in Liquid Ammonia.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Reducing oligosaccharides via glycal assembly: on the remarkable stability of anomeric hydroxyl groups to global deprotection with sodium in liquid ammonia

Abstract Several partially benzylated 1-hydroxy sugars were rapidly deprotected by sodium/liquid ammonia. The terminal hemiketal linkage of the substrates remained intact under these conditions and does not generate ring-opened alditols. Peracetylated glucose and glucosamine derivatives were obtained in 64–79% isolated yields.

A Useful and Convenient Synthetic Procedure for Hydrolysis of Thioglycosides

Abstract Various thioglycosides 1 are smoothly hydrolyzed chemoselectively to the corresponding 1-hydroxy sugars 2 in good yields at 0–5 °C by employing (NH4)6Mo7O24·4H2O-H2O2 or H2MoO4·H2O-H2O2 to promote oxidation of ammonium bromide in the presence of perchloric acid in CH2Cl2-H2O solvent system. Mild conditions, good yields, no side reactions such as bromination either at the anomeric position or double bond, and even oxidation at the sulfur are some of the major advantages.