Glycosyl Disulfides Research Articles

Direct Synthesis of Unsymmetrical Glycosyl Disulfides from Glycosyl Bromides

AbstractA significantly fast one step reaction condition has been developed for the synthesis of unsymmetrical anomeric glycosyl disulfide derivatives in excellent yield by the treatment of anomeric glycosyl bromides with a combination of carbon disulfide (CS2) and sodium sulfide nonahydrate (Na2S ⋅ 9H2O) in the presence of symmetrical alkyl, aryl and glycosyl disulfides at room temperature. Exclusive formation of anomerically beta‐disulfides was observed under the reaction conditions. Most of the reactions are high yielding and suitable for scale‐up synthesis.

Preparation of glycosyl disulfides and sulfides via the formation of glycosyl Bunte salts as thiol surrogates

A convenient odourless reaction condition has been developed for the preparation of symmetrical glycosyl disulfide derivatives and aryl glycosyl disulfide derivatives from corresponding glycosyl iodides via in situ formation of glycosyl Bunte salts as thiol surrogates. The reaction has been further extended towards the preparation of glycosyl sulfides derivatives from corresponding Bunte salt in the presence of sodium sulphide. Most of the reactions were high yielding and suitable for scaling up.

Glycosyl disulfides: importance, synthesis and application to chemical and biological systems.

The disulfide bond plays an important role in the formation and stabilisation of higher order structures of peptides and proteins, while in recent years interest in this functional group has been extended to carbohydrate chemistry. Rarely found in nature, glycosyl disulfides have attracted significant attention as glycomimetics, with wide biological applications including lectin binding, as key components of dynamic libraries to study carbohydrate structures, the study of metabolic and enzymatic studies, and even as potential drug molecules. This interest has been accompanied and fuelled by the continuous development of new methods to construct the disulfide bond at the anomeric centre. Glycosyl disulfides have also been exploited as versatile intermediates in carbohydrate synthesis, particularly as glycosyl donors. This review focuses on the importance of the disulfide bond in glycobiology and in chemistry, evaluating the different methods available to synthesise glycosyl disulfides. Furthermore, we review the role of glycosyl disulfides as intermediates and/or glycosyl donors for the synthesis of neoglycoproteins and oligosaccharides, before finally considering examples of how this important class of carbohydrates have made an impact in biological and therapeutic contexts.

The Oxidation of S‐Acetyl by Nitrite: Mechanism and Application

AbstractStraightforward S‐S bond formation via the oxidation of S‐acetyl group by nitrite was observed and the mechanism was explored in this study. The observed reaction was found to be initiated via a S‐nitrosylation followed by the S‐S bond formation that accompanies nitrite oxide (NO) release. The reaction approach was further analyzed by quantum chemical studies, surpporting a mechanism of first generating nitrous ester. Unlike S‐nitrosylation between thiols and nitrite proceeding at a strong alkaline condition due to the formation of hydroxyl anion, the S‐nitrosylation between S‐acetyl and nitrite proceed at a condition close to neutrality due to the formation of acetate instead. Using this reaction, per‐O‐acetylated glycosyl disulfides were obtained in high yields at mild condition. Furthermore, per‐O‐acetylated glycosyl 1‐thiols were also efficiently prepared starting from per‐acetylated 1‐thio‐glycoses in a one‐pot reaction including the oxidation of S‐acetyl group by nitrite and the reduction of disulfides.

Straightforward S-S Bond Formation via the Oxidation of S-Acetyl by Iodine in the Presence of N-Iodosuccinimide.

Straightforward S-S bond formation via the oxidation of S-acetyl group by iodine was reported here. The reaction was further applied in the synthesis of per-O-acetylated glycosyl disulfides. These studies demonstrated great improvement in reaction rate, yield, and general convenience in the presence of N-iodosuccinimide. Furthermore, selectively deacetylated glycosyl thiols were obtained in high yields when these per-O-acetylated glycosyl disulfides were reduced with tris(2-carboxyethyl)-phosphine (TCEP). Our method supplied an efficient way to obtain both per-O-acetylated glycosyl disulfides and per-O-acetylated glycosyl thiols in which the sulfur group was located at any position.

Novel strategies for the synthesis of unsymmetrical glycosyl disulfides.

Novel strategies for the efficient synthesis of unsymmetrical glycosyl disulfides are reported. Glycosyl disulfides are increasingly important as glycomimetics and molecular probes in glycobiology. Sialosyl disulfides are synthesised directly from the chlorosialoside Neu5Ac2Cl, proceeding via a thiol-disulfide exchange reaction between the sialosyl thiolate and symmetrical disulfides. This methodology was adapted and found to be successfully applicable to the synthesis of unsymmetrical glucosyl disulfides under mild conditions.

Synthesis of mixed glycosyl disulfides/selenenylsulfides using benzyltriethylammonium tetrathiomolybdate as a sulfur transfer reagent

An easy and mild method has been developed for the synthesis of mixed glycosyl disulfides/selenenylsulfides from glycosyl halides and diaryl/dialkyl dichalcogenides in the presence of benzyltriethylammonium tetrathiomolybdate [(BnEt3N)2MoS4]. The salient feature of this method is the sulfur transfer from [BnEt3N]2MoS4 to form glycosyl disulfides which with excess tetrathiomolybdate further undergo exchange reaction with other dichalcogenides in a one-pot operation.

ChemInform Abstract: Synthesis of Glycosyl Disulfides Containing an α‐Glycosidic Linkage.

AbstractA wide range of symmetrical and unsymmetrical glycosyl disulfides are synthesized with focus on the use of α‐glycosyl thiols.

Synthesis of glycosyl disulfides containing an α-glycosidic linkage

A wide range of symmetrical and unsymmetrical glycosyl disulfides is synthesized with focus on the use of α-glycosyl thiols. Oxidation of α-glycosyl thiols with iodine leads to symmetrical α,α-glycosyl disulfides, while unsymmetrical disulfides are readily synthesized from α- and β-glycosyl thiols under the action of DDQ. Thus, glycosyl disulfides containing at least one α-glycosidic linkage are made available.

Aromatic glycosyl disulfide derivatives: Evaluation of their inhibitory activities against Trypanosoma cruzi

Aromatic oligovalent glycosyl disulfides and some diglycosyl disulfides were tested against three different Trypanosoma cruzi strains. Di-(β-d-galactopyranosyl-dithiomethylene) benzenes 2b and 4b proved to be the most active derivatives against all three strains of cell culture-derived trypomastigotes with IC50 values ranging from 4 to 11μM at 37°C. The inhibitory activities were maintained, although somewhat lowered, at a temperature of 4°C as well. Three further derivatives displayed similar activities against at least one of the three strains. Low cytotoxicities of the active compounds, tested on confluent HeLa, Vero and peritoneal macrophage cell cultures, resulted in significantly higher selectivity indices (SI) than that of the reference drug benznidazole. Remarkably, several molecules of the tested panel strongly inhibited the parasite release from T. cruzi infected HeLa cell cultures suggesting an effect against the intracellular development of T. cruzi amastigotes as well.

Glycosylated Eumelanin Building Blocks by Thioglycosylation of 5,6‐Diacetoxyindole with an Expedient Selenium‐Based Dynamic‐Mixture Methodology

AbstractA series of 3‐thioglycosylated 5,6‐diacetoxyindole derivatives, which are important tools for eumelanin research and application, were prepared through a practical and efficient approach exploiting a dynamic mixture of thioglycoside agents. The strategy is feasible for installing both mono‐ and disaccharide units and relies on the facile in situ conversion of glycosyl disulfides into the corresponding, more reactive, phenylselenenyl sulfides in the presence of diphenyl diselenide, N‐bromosuccinimide (NBS) and tetrabutylammonium bromide (TBAB).

A straightforward synthetic access to symmetrical glycosyl disulfides and biological evaluation thereof

Symmetrical glycosyl disulfides can be prepared within a few hours from per-O-acetylated precursors via a sequential approach entailing short reactions and no purification of any intermediate. The final thiolate-to-disulfide oxidation step is noticeably accelerated by low amounts of phenyl diselenide under air. Applicability of the strategy to non-saccharidic symmetrical alkyl disulfides has also been examined. A preliminary assay of the cytotoxic activity of symmetrical 1,1'- disulfides was performed on two human tumor cell lines, and a noteworthy activity was recorded for a range of these synthetic compounds.

A high-yielding, one-pot preparation of unsymmetrical glycosyl disulfides using 1-chlorobenzotriazole as an in situ trapping/oxidizing agent

A high-yielding, one-pot methodology for preparing unsymmetrical glycosyl disulfides derived from sugar, alkyl/aryl or cysteine thiols is reported using 1-chlorobenzotriazole (BtCl) as the oxidant. The highlight of the method is the low temperature of coupling (−78 °C) as well as the in situ trapping of the sulfenyl intermediate, which ensures that no homodimer of R 1SH (R 1SSR 1) is formed. The coupling efficiency is independent of sugar type, thiol position in the sugar, sugar-protecting groups, and the various products serve to illustrate the rapid synthetic access to a number of model systems in glycobiology.

Efficient one-pot synthesis of glycosyl disulfides

Methodology for the efficient and facile synthesis of glycosyl disulfides is reported. A one-pot procedure employing mild conditions using diethyl azodicarboxylate is described to synthesise a series of glycosyl disulfides in excellent yields.

Glycosyl Disulfides: Novel Glycosylating Reagents with Flexible Aglycon Alteration

[reaction: see text] Glycosyl disulfides have been shown for the first time to be effective glycosyl donors. Glucosylation and galactosylation of a panel of representative alcohol acceptors allowed the formation of 28 simple glycosides, disaccharides, and glycoamino acids in yields of up to 90%. As well as providing a novel class of effective glycosyl donors, the ability to easily alter the nature of the aglycon and the ability to differently activate donors that differ only in their aglycon simply through altering conditions lends glycosyl disulfide donors to their use in latent-active reactivity tuning strategies.

Glycosyldisulfides: a new class of solution and solid phase glycosyl donors

Mixed glycosyl disulfides are not only glycomimetics but also glycosyl donors that may be readily constructed in either armed ether-protected or disarmed ester-protected and in soluble or solid-supported forms from corresponding glycosyl methanethiosulfonates and used in the glycosylation of a variety of representative acceptors.