Stable Glycosyl Donors Research Articles

Synthesis of N‐Glycosides by Silver‐Assisted Gold Catalysis

AbstractThe synthesis of N‐glycosides from stable glycosyl donors in a catalytic fashion is still challenging, though they exist ubiquitously in DNA, RNA, glycoproteins, and other biological molecules. Herein, silver‐assisted gold‐catalyzed activation of alkynyl glycosyl carbonate donors is shown to be a versatile approach for the synthesis of purine and pyrimidine nucleosides, asparagine glycosides and quinolin‐2‐one N‐glycosides. Thus synthesized nucleosides were subjected to the oxidation–reduction sequence for the conversion of Ribf‐ into Araf‐ nucleosides, giving access to nucleosides that are otherwise difficult to synthesize. Furthermore, the protocol is demonstrated to be suitable for the synthesis of 2’‐modified nucleosides in a facile manner. Direct attachment of an asparagine‐containing dipeptide to the glucopyranose and subsequent extrapolation to afford the dipeptide disaccharide unit of chloroviruses is yet another facet of this endeavor.

Synthesis of N-Glycosides by Silver-Assisted Gold Catalysis.

The synthesis of N-glycosides from stable glycosyl donors in a catalytic fashion is still challenging, though they exist ubiquitously in DNA, RNA, glycoproteins, and other biological molecules. Herein, silver-assisted gold-catalyzed activation of alkynyl glycosyl carbonate donors is shown to be a versatile approach for the synthesis of purine and pyrimidine nucleosides, asparagine glycosides and quinolin-2-one N-glycosides. Thus synthesized nucleosides were subjected to the oxidation-reduction sequence for the conversion of Ribf- into Araf- nucleosides, giving access to nucleosides that are otherwise difficult to synthesize. Furthermore, the protocol is demonstrated to be suitable for the synthesis of 2'-modified nucleosides in a facile manner. Direct attachment of an asparagine-containing dipeptide to the glucopyranose and subsequent extrapolation to afford the dipeptide disaccharide unit of chloroviruses is yet another facet of this endeavor.

Novel eco-friendly solution for the regioselective acetylation of per-O-TMS carbohydrates

Regioselective acetylation of per-O-TMS carbohydrates was achieved preferentially at the 6 position or 1,6-position under mild conditions involving the eco-friendly solvent acetonitrile, at room temperature, in ambient atmosphere and in a shorter time. Good or moderate yields were obtained via 4-dimethylaminopyridine, without auxiliary equipment. A single α-O-Acetyl acetylation anomer was exclusively defined for the involved substrates. A 6-O-monoacetate derivative was applied and used as a stable glycosyl donor in the disaccharides construction. The methodology was successful for a range of substrates, which include the following: d-lactose, d-trehalose, d-galactose, methyl α-d-galactose, d-glucose, d-mannose, d-xylose, and l-fucose.

Stable Alkynyl Glycosyl Carbonates: Catalytic Anomeric Activation and Synthesis of a Tridecasaccharide Reminiscent of Mycobacterium tuberculosis Cell Wall Lipoarabinomannan

AbstractOligosaccharide synthesis is still a challenging task despite the advent of modern glycosidation techniques. Herein, alkynyl glycosyl carbonates are shown to be stable glycosyl donors that can be activated catalytically by gold and silver salts at 25 °C in just 15 min to produce glycosides in excellent yields. Benzoyl glycosyl carbonate donors are solid compounds with a long shelf life. This operationally simple protocol was found to be highly efficient for the synthesis of nucleosides, amino acids, and phenolic and azido glycoconjugates. Repeated use of the carbonate glycosidation method enabled the highly convergent synthesis of tridecaarabinomannan in a rapid manner.

Stable Alkynyl Glycosyl Carbonates: Catalytic Anomeric Activation and Synthesis of a Tridecasaccharide Reminiscent of Mycobacterium tuberculosis Cell Wall Lipoarabinomannan.

Oligosaccharide synthesis is still a challenging task despite the advent of modern glycosidation techniques. Herein, alkynyl glycosyl carbonates are shown to be stable glycosyl donors that can be activated catalytically by gold and silver salts at 25 °C in just 15 min to produce glycosides in excellent yields. Benzoyl glycosyl carbonate donors are solid compounds with a long shelf life. This operationally simple protocol was found to be highly efficient for the synthesis of nucleosides, amino acids, and phenolic and azido glycoconjugates. Repeated use of the carbonate glycosidation method enabled the highly convergent synthesis of tridecaarabinomannan in a rapid manner.

Controlled Synthesis of O-Glycopolypeptide Polymers and Their Molecular Recognition by Lectins

The facile synthesis of high molecular weight water-soluble O-glycopolypeptide polymers by the ring-opening polymerization of their corresponding N-carboxyanhydride (NCA) in very high yield (overall yield > 70%) is reported. The per-acetylated-O-glycosylated lysine-NCA monomers, synthesized using stable glycosyl donors and a commercially available protected amino acid in very high yield, was polymerized using commercially available amine initiators. The synthesized water-soluble glycopolypeptides were found to be α-helical in aqueous solution. However, we were able to control the secondary conformation of the glycopolypeptides (α-helix vs nonhelical structures) by polymerizing racemic amino acid glyco NCAs. We have also investigated the binding of the glycopolypeptide poly(α-manno-O-lys) with the lectin Con-A using precipitation and hemagglutination assays as well as by isothermal titration calorimetry (ITC). The ITC results clearly show that the binding process is enthalpy driven for both α-helical and nonhelical structures, with negative entropic contribution. Binding stoichiometry for the glycopolypeptide poly(α-manno-O-lys) having a nonhelical structure was slightly higher as compared to the corresponding polypeptide which adopted an α-helical structure.

2-Allylphenyl glycosides as glycosyl donors for sugar coupling

Glycosylations employing 2-allylphenyl glycoside, a new type of stable glycosyl donor, were optimized and explored with a variety of acceptors promoted by ICl/AgOTf. The utility of the protocol was further demonstrated with an efficient synthesis of the disaccharide fragment of bleomycins.

Synthesis of glycopolypeptides by the ring opening polymerization of O-glycosylated-α-amino acid N-carboxyanhydride (NCA)

The novel synthesis of O-glycosylated lysine-NCA from a stable glycosyl donor and a commercially available protected amino acid in very high yield is reported. These O-glycosylated lysine-NCA monomers underwent ring opening polymerization using simple primary amine initiators to form well defined, high molecular weight homoglycopolypeptides and diblock co-glycopolypeptides. The synthesis of azide labelled end functionalized glycopolypeptides and amphiphilic diblock copolypeptides is also reported. This methodology represents an easy and practical route to the synthesis of O-glycosylated polypeptides with 100% glycosylation.

Superarming Common Glycosyl Donors by Simple 2-O-Benzoyl-3,4,6-tri-O-benzyl Protection

A complementary concept for superarming glycosyl donors through the use of common protecting groups was previously discovered with S-benzoxazolyl (SBox) glycosyl donors. As this strategy can be of benefit to existing oligosaccharide methodologies, it has now been expanded to encompass a wide array of common, stable glycosyl donors. The versatility of this developed technique has been further illustrated in application to a sequential chemoselective oligosaccharide synthesis, wherein a superarmed ethyl thioglycoside was incorporated into the conventional armed-disarmed strategy.

Propargyl Glycosides as Stable Glycosyl Donors: Anomeric Activation and Glycoside Syntheses.

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.

Propargyl Glycosides as Stable Glycosyl Donors: Anomeric Activation and Glycoside Syntheses

The advantages of stable glycosyl donors for saccharide coupling are many, and we describe herein the utility of propargyl glycosides for anomeric activation and glycoside synthesis exploiting the alkynophilicity of AuCl3. Various aglycones were reacted with propargyl glycosides, resulting in the formation of an alpha,beta-mixture of glycosides and disaccharides in good yields.

An Efficient Method for Catalytic Stereoselective Synthesis of α-l-Fucopyranosides

Abstract A new efficient method for the catalytic stereoselective synthesis of various α-l-fucosides by using an easily available and stable glycosyl donor, 2,3,4-tri-O-benzyl-l-fucopyranosyl methoxyacetate, is established. Also, trimethylsilyl trifluoroacetate and lithium perchlorate are found to be effective additives in the synthesis of Fucα1-3GlcNAc and Fucα1-4GlcNAc linkages.

ChemInform Abstract: Epoxides Derived from Pyranosyl Dienes: Unusually Stable Glycosyl Donors.

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.

Epoxides derived from pyranosyl dienes: Unusually stable glycosyl donors

A pyranosyl diene appropriately substituted for use in a total synthesis of staurosporine has been synthesized. The mono-epoxides and bis-epoxides obtained from treatment of this diene with dimethyldioxirane are unusually stable.

ChemInform Abstract: Glycoside and Saccharide Synthesis Using N‐Glycosyltriazoles as Hydrolytically Stable Glycosyl Donors.

AbstractDiels‐Alder reaction of the tetra‐O‐pivaloyl‐β‐D‐glucopyranosyl azide (I) with the dialkyl acetylenedicarboxylates (II) in toluene yields the hydrolytically stable N‐glycosyltriazoles (III) which serve as glycosyl donors.

Glycoside and Saccharide Synthesis UsingN-Glycosyl Triazoles as Hydrolytically Stable Glycosyl Donors

Hydrolytically stable N 1-glycosyl triazoles formed from glycosyl azides as anomerically protected precursors are used as the glycosyl donors in the synthesis of steroid glycosides, phenyl glycosides, glycosyl amino acid derivatives and disaccharides after activation with trimethylsilyl trifluoromethanesulfonate.