Aryl Glycosides Research Articles

Characterization of a novel GH30 non-specific endoxylanase AcXyn30B from Acetivibrio clariflavus.

The xylanolytic enzymes Clocl_1795 and Clocl_2746 from glycoside hydrolase (GH) family 30 are highly abundant in the hemicellulolytic system of Acetivibrio clariflavus (Hungateiclostridium, Clostridium clariflavum). Clocl_1795 has been shown to be a xylobiohydrolase AcXbh30A releasing xylobiose from the non-reducing end of xylan and xylooligosaccharides. In this work, biochemical characterization of Clocl_2746 is presented. The protein, designated AcXyn30B, shows low sequence similarity to other GH30 members and phylogenetic analysis revealed that AcXyn30B and related proteins form a separate clade that is proposed to be a new subfamily GH30_12. AcXyn30B exhibits similar specific activity on glucuronoxylan, arabinoxylan, and aryl glycosides of linear xylooligosaccharides suggesting that it is a non-specific xylanase. From polymeric substrates, it releases the fragments of degrees of polymerization (DP) 2-6. Hydrolysis of different xylooligosaccharides indicates that AcXyn30B requires at least four occupied catalytic subsites for effective cleavage. The ability of the enzyme to hydrolyze a wide range of substrates is interesting for biotechnological applications. In addition to subfamilies GH30_7, GH30_8, and GH30_10, the newly proposed subfamily GH30_12 further widens the spectrum of GH30 subfamilies containing xylanolytic enzymes. KEY POINTS: Bacterial GH30 endoxylanase from A. clariflavus (AcXyn30B) has been characterized AcXyn30B is non-specific xylanase hydrolyzing various xylans and xylooligosaccharides Phylogenetic analysis placed AcXyn30B in a new GH30_12 subfamily.

Characterization of a novel cold-adapted GH1 β-glucosidase from Psychrobacillus glaciei and its application in the hydrolysis of soybean isoflavone glycosides

The novel β-glucosidase gene (pgbgl1) of glycoside hydrolase (GH) family 1 from the psychrotrophic bacterium Psychrobacillus glaciei sp. PB01 was successfully expressed in Escherichia coli BL21 (DE3). The deduced PgBgl1 contained 447 amino acid residues with a calculated molecular mass of 51.4 kDa. PgBgl1 showed its maximum activity at pH 7.0 and 40 °C, and still retained over 10% activity at 0 °C, suggesting that the recombinant PgBgl1 is a cold-adapted enzyme. The substrate specificity, Km, Vmax, and Kcat/Km for the p-Nitrophenyl-β-D-glucopyranoside (pNPG) as the substrate were 1063.89 U/mg, 0.36 mM, 1208.31 U/mg and 3871.92/s, respectively. Furthermore, PgBgl1 demonstrated remarkable stimulation of monosaccharides such as glucose, xylose, and galactose, as well as NaCl. PgBgl1 also demonstrated a high capacity to convert the primary soybean isoflavone glycosides (daidzin, genistin, and glycitin) into their respective aglycones. Overall, PgBgl1 exhibited high catalytic activity towards aryl glycosides, suggesting promising application prospects in the food, animal feed, and pharmaceutical industries.

Visible light induced palladium-catalyzed Suzuki–Miyaura cross-coupling of glycosyl chlorides to form C-aryl glycosides

A powerful method is developed utilizing excited-state palladium-catalyzed Suzuki–Miyaura reaction to synthesize C-aryl glycosides. It can be applied to a wide range of aryl and heteroaryl boronic ester substrates as well as glycosyl chlorides.

On the origin of the electronic and magnetic circular dichroism of naphthyl C-glycosides: Anomeric configuration

Aryl C-glycosides, in which the glycosidic bond is changed to a carbon–carbon bond, are an important family of biologically-active compounds. They often serve as secondary metabolites or exhibit antibiotic and cytostatic activities. Their stability to hydrolysis has made them attractive targets for new drugs. Their conformational behavior often strongly influences the resulting function. Their detailed structural and conformational description is thus highly desirable.This work studies the structure of three different naphthyl C-glycosides using UV–vis absorption as well as electronic and magnetic circular dichroism. It also describes their conformational preferences using a combination of molecular dynamics and DFT calculations. The reliability of these preferences has been verified by simulations of spectral properties and a comparison with their measured spectra. In particular, ECD spectroscopy has been shown to distinguish easily between α- and β-pseudoanomers of aryl C-glycosides. Computer simulations and spectral decomposition have revealed how the resulting ECD patterns of the naphthyl glycosides studied are influenced by different conformer populations. In conclusion, reliable ECD patterns cannot be calculated by separating the naphthyl rotation from other conformational motions. MCD patterns have been similar for all the naphthyl C-glycosides studied. No clear diagnostic features have been found for either the pseudoanomeric configuration or the preferred hydroxymethyl rotamer. Nevertheless, the work has demonstrated the potential of MCD for the study of aryl glycosides interacting with proteins.

Synthesis, crystal structure, DFT calculation and confirmation of absolute configuration of empagliflozin

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by long-term disruptions in metabolism. In the course of drug development over the past decades, sodium-glucose cotransporter 2 (SGLT2) has emerged as a novel therapeutic target for treating T2DM. Empagliflozin, a significant pharmacologically active aryl glycoside, functions as a sodium-glucose cotransporter 2 (SGLT2) inhibitor and has been extensively used for blood glucose control in patients with both T2DM and diagnosed cardiovascular disease (CVD). In this study, empagliflozin was synthesized through a six-step reaction and subjected to single-crystal growth, with its structure analyzed via X-ray diffraction. Subsequently, comprehensive computational predictions of empagliflozin's structural properties were carried out using DFT theory, encompassing infrared, nuclear magnetic resonance, Raman spectra, and ECD measurements. The results were subjected to a combined analysis with experimental data, bearing significant implications for the spectral analysis and absolute configuration determination of empagliflozin. In order to gain insights into the reasons behind the formation of empagliflozin crystals, a single crystal structure analysis was performed. Additionally, DFT calculations were employed to investigate various physicochemical properties of empagliflozin, including RDG, ELF, FMOs, MEP, etc. This study aimed to provide insights into the physicochemical properties of empagliflozin and its various non-covalent interactions. The findings are anticipated to provide valuable insights for subsequent structure optimization and drug discovery endeavors.

Efficient Synthesis of Natural Product Inspired Naphthoquinone-Fused Glycohybrids and Their In Silico Docking Studies

AbstractNaphthoquinones, a diverse group of natural compounds with a 1,4-naphthoquinone core structure, have gained attention for their pharmacological properties. The anticancer activity of these compounds is attributed to their ability to accept electrons, leading to the generation of reactive oxygen species that cause DNA damage and cell death. In recent studies, hydroxy-1,4-naphthoquinone derivatives, including daunorubicin, have shown promising inhibitory effects against several human cancers, such as acute myeloid leukemia, chronic myelogenous leukemia, and Kaposi’s sarcoma. To further explore their potential as anticancer agents, this research article focuses on the design and synthesis of natural product inspired naphthoquinone-based glycohybrids. These glycohybrids are designed based on the structures of bioactive aryl glycosides and quinones, aiming to enhance their binding affinity and specificity towards cancer-related protein targets. The interactions between the synthesized glycohybrids and target proteins through computational docking simulations has been studied and better binding affinity was found.

Synthesis of C-Aryl Glycosides by C-H Functionalization.

In recent years, the synthesis of C-aryl glycosides hrough C-H functionalization has attracted extensive attention of organic synthesis chemists due to its steps and atomic economy. In this concept, we systematically summarizes the synthesis of C-aryl glycosides with diverse regioselectivity and diastereoselectivity from the perspective of C-H arylation of glycosides and C-H glycosylation of arenes. It can be found that a series of recently developed C-H glycosylation reactions have higher site-selectivity and diastereomeric selectivity than Friedel-Crafts glycosylation reaction. The reaction conditions are milder, which can be compatible with acid-sensitive protective groups, such as acetals or ketals, and the deprotection is more convenient. It can be seen that there are few reports on remote C-H glycosylation of aromatic hydrocarbons, which is a new field and needs further research. In addition, C-H glycosylation has a lot of shortcomings, which need to be further explored: a) the precise regulation of stereoselectivity in the reaction process also needs further optimization; b) the research on the reaction mechanism is almost limited to DFT calculation, and there is no exact experimental evidence. For key parts, such as the specific reaction mechanism between cyclo-metal intermediates and glycosyl donors in ortho-CAr -H glycosylation is still unclear; c) due to the fact that aryl glycoside compounds contain bare hydroxyl groups in practical applications, it is an urgent problem to realize the compatibility of glycoside substrates containing naked hydroxyl groups or to remove the protective groups on hydroxyl groups by a mild and efficient method after the reaction; d) In this rapidly developing field, we need to study a greener, more economical and more practical C-H glycosylation of arenes in the future, which will be conducive to the synthesis of C-aryl glycosides with more biological application significance.

Phase-Transfer Catalyzed Microfluidic Glycosylation: A Small Change in Concentration Results in a Dramatic Increase in Stereoselectivity

Phase-transfer catalysis (PTC) is widely used in glycochemistry for the preparation of aryl glycosides by the glycosylation reaction. While investigating the possibility of synthesis of 4-(3-chloropropoxy)phenyl sialoside (Neu5Ac-OCPP) from N-acetylsialyl chloride with O-acetyl groups (1), we have recently discovered a strong dependence of the PTC glycosylation outcome on the mixing mode: under batch conditions, only α-anomer of Neu5Ac-OCPP was obtained, albeit in low yield (13%), while under microfluidic conditions the yield of Neu5Ac-OCPP increased to 36%, although stereoselectivity decreased (α/β ≤ 6.2). Here, we report that the outcome of this reaction, performed under microfluidic conditions using a Comet X-01 micromixer (at 2 μL/min flow rate), non-linearly depends on the concentration of N-acetylsialyl chloride 1 (5–200 mmol/L). The target Neu5Ac-OCPP was obtained in a noticeably higher yield (up to 66%) accompanied by enhanced stereoselectivity (α/β = 17:1–32:1) in the high concentration range (C > 50 mmol/L), whereas the yield (10–36%) and especially, stereoselectivity (α/β = 0.9:1–6.2:1) were lower in the low concentration range (C ≤ 50 mmol/L). This dramatic stepwise increase in stereoselectivity above critical concentration (50 mmol/L) is apparently related to the changes in the presentation of molecules on the surface of supramers of glycosyl donor, which exist in different concentration ranges.

Visible-light-induced electron donor–acceptor (EDA) complex-initiated synthesis of non-anomeric S-aryl glycosides

A visible-light-induced protocol for the preparation of S-aryl thioglycosides has been reported.

Synthesis of C‐Aryl Glycosides via Ru‐Catalyzed Remote C−H Glycosylation of 8‐Aminoquinoline Amides

AbstractC‐Aryl glycoside is a class of structural motifs with important medicinal value. Herein, a remote C−H glycosylation strategy enabled by Ruthenium(II)‐catalyzed with mostly α‐stereoselectivity is described. This approach exhibits great functional group compatibility with various glycosides and arylamides. A series of experiments provided strong evidence for the free radical mechanism and reversible C−H activation process, and a possible mechanism was proposed.magnified image

Ruthenium‐Catalyzed Stereo‐ and Site‐Selective ortho‐ and meta‐C−H Glycosylation and Mechanistic Studies

AbstractC‐aryl glycosides are popular basic skeletons in biochemistry and pharmaceutical chemistry. Herein, ruthenium‐catalyzed highly stereo‐ and site‐selective ortho‐ and meta‐CAr−H glycosylation is described. A series of C‐aryl pyranosides and furanosides were synthesized by this method. The strategy showed good substrate scope, and various N‐heterocyclic directing groups were compatible with the reaction system. A mechanistic study suggested that the key pathway of ortho‐CAr−H glycosylation might involve oxidative addition/reduction elimination, whereas aryl meta‐C−H glycosylation was mediated by σ‐activation. Density functional theory calculations also showed that the high stereoselectivity of meta‐CAr−H glycosylation was due to steric hindrance.

Production of Daidzein and Genistein from Seed and Root Extracts of Korean Wild Soybean (Glycine soja) by Thermostable β-Galactosidase from Thermoproteus uzoniensis

Isoflavone glycosides are commonly biotransformed into isoflavone aglycones due to the superior biological activities of the latter. Wild soybeans contain a higher isoflavone content than domesticated soybeans due to their high level of genetic diversity. In this study, we cloned and characterized a thermostable β-galactosidase from the extreme thermophile Thermoproteus uzoniensis for potential application in isoflavone conversion in Korean wild soybeans. The purified recombinant enzyme exhibited a maximum specific activity of 1103 μmol/min/mg at pH 5.0 and 90 °C with a half-life of 46 h and exists as a homodimer of 113 kDa. The enzyme exhibited the highest activity for p-nitrophenyl (pNP)-β-D-galactopyranoside among aryl glycosides and it hydrolyzed isoflavone glycosides in the order genistin > daidzin > ononin > glycitin. The enzyme completely hydrolyzed 2.77 mM daidzin and 3.85 mM genistin in the seed extract of wild soybean after 80 and 70 min with productivities of 1.86 and 3.30 mM/h, respectively, and 9.89 mM daidzin and 1.67 mM genistin in the root extract after 180 and 30 min, with the highest productivities of 3.30 and 3.36 mM/h, respectively, compared to other glycosidases. Our results will contribute to the industrial production of isoflavone aglycone using wild soybean and this is the first report on the enzymatic production of isoflavone aglycones from isoflavone glycosides in wild soybeans.

Dynamic Tuning in Synthetic Glycosidase for Selective Hydrolysis of Alkyl and Aryl Glycosides.

Enzymes use sophisticated conformational control to optimize the dynamics of their protein framework for efficient catalysis. Although it is difficult to employ a similar strategy to improve catalysis in a synthetic enzyme, we here report that modulation of the dynamics of the substrate in the active site is readily achievable in a complex between a molecularly imprinted nanoparticle and its acid cofactor, through tuning of the size and shape of the imprinted site. As the alkyl glucoside substrate is bound with increasing strength and held in a more tightly fitted pocket, the acid-catalyzed glycan hydrolysis becomes more difficult. A larger, wider active site, although less able to bind the substrate, affords a higher catalytic activity, likely due to easier alignment of the substrate and the acid cofactor for a general acid catalysis. The substrate selectivity is controlled by both the tightness of the aglycon-binding site and the orientation of the glycan-binding boroxole group.

Black Swan in Phase Transfer Catalysis: Influence of Mixing Mode on the Stereoselectivity of Glycosylation

AbstractPhase transfer catalysis (PTC) is widely used for the preparation of anomerically pure aryl glycosides by glycosylation of phenols with glycosyl halides. Here, we attempted to synthesize 4‐(3‐chloropropoxy)phenyl (CPP) sialoside – a useful Janus glycoside for neoglycoconjugate synthesis. A batch glycosylation reaction under typical PTC conditions (N‐acetylsialyl chloride, 4‐(3‐chloropropoxy)phenol, Bu4NHSO4, AcOEt, 10 % aq Na2CO3) resulted in formation of CPP sialoside as a single anomer, albeit in low yield. Conversely, the PTC glycosylation in flow using Comet X‐01 micromixer doubled the yield of CPP sialoside, which was obtained as a mixture of anomers suggesting the change in the reaction mechanism apparently induced by the change in mixing mode. An increase in flow rate led to further loss of stereoselectivity while the use of T‐shaped mixer increased stereoselectivity. Similar results were obtained for N,N‐diacetylsialyl chloride and two other para‐alkoxy‐substituted phenols suggesting generality of the discovered phenomenon.

Protecting group free glycosylation: one-pot stereocontrolled access to 1,2-trans glycosides and (1→6)-linked disaccharides of 2-acetamido sugars.

Unprotected 2-acetamido sugars may be directly converted into their oxazolines using 2-chloro-1,3-dimethylimidazolinium chloride (DMC), and a suitable base, in aqueous solution. Freeze drying and acid catalysed reaction with an alcohol as solvent produces the corresponding 1,2-trans-glycosides in good yield. Alternatively, dissolution in an aprotic solvent system and acidic activation in the presence of an excess of an unprotected glycoside as a glycosyl acceptor, results in the stereoselective formation of the corresponding 1,2-trans linked disaccharides without any protecting group manipulations. Reactions using aryl glycosides as acceptors are completely regioselective, producing only the (1→6)-linked disaccharides.

Dapagliflozin – structure, synthesis, and new indications

Dapagliflozin is a sodium-glucose co-transporter-2 (SGLT2) inhibitors used in the treatment of patients with type 2 diabetes. An aryl glycoside with significant effect as glucose-lowering agents, Dapagliflozin also has indication for patients with Heart Failure and Chronic Kidney Disease. This review examines the structure, synthesis, analysis, structure activity relationship and uses of the product. The studies behind this drug have opened the doors for the new line of treatment – a drug that reduces blood glucoses, decreases the rate of heart failures, and has a positive effect on patients with chronic kidney disease.

Comprehensive structure–activity relationship (SAR) investigation of C-aryl glycoside derivatives for the development of SGLT1/SGLT2 dual inhibitors

Multi-combined computational approaches were used to explore the SAR and design novel potential SGLT1/SGLT2 dual inhibitors.

Synthesis of Arylated Carbohydrates and Their Application

N- and O-arylated carbohydrates except for aryl glycosides are not found in nature. Therefore, based on their structure, these derivatives are expected as new functional molecules. However, the synthesis of arylated carbohydrates has not been thoroughly investigated and few studies have been reported their application. Hence, our research focused on the elucidation of the arylated carbohydrates function. Various N-arylated carbohydrates were synthesized using the Buchwald-Hartwig reaction, while O-arylated carbohydrates were obtained by employing hypervalent iodine reagents. Based on these compounds, we succeeded in developing novel fluorescently labeled glucose derivatives, aryl-based protecting groups, and a stereoselective glycosylation.

Modular and Stereoselective Synthesis of C-Aryl Glycosides via Catellani Reaction.

In this work, we describe a Catellani-type C-H glycosylation to provide rapid access to various highly decorated α-C-(hetero)aryl glycosides in a modular and stereoselective manner (>90 examples). The termination step is flexible, which is demonstrated by ipso-Heck reaction, hydrogenation, Suzuki coupling, and Sonogashira coupling. Application of this methodology has been showcased by preparing glycoside-pharmacophore conjugates and a dapagliflozin analogue. Notably, the technology developed herein represents an unprecedented example of Catellani-type alkylation involving an SN1 pathway.

Scope of the DMC mediated glycosylation of unprotected sugars with phenols in aqueous solution.

Activation of reducing sugars in aqueous solution using 2-chloro-1,3-dimethylimidazolinium chloride (DMC) and triethylamine in the presence of para-nitrophenol allows direct stereoselective conversion to the corresponding 1,2-trans para-nitrophenyl glycosides without the need for any protecting groups. The reaction is applicable to sulfated and phosphorylated sugars, but not to ketoses or uronic acids or their derivatives. When applied to other phenols the product yield was found to depend on the pKa of the added phenol, and the process was less widely applicable to 2-acetamido sugars. For 2-acetamido substrates an alternative procedure in which the glycosyl oxazoline was pre-formed, the reaction mixture freeze-dried, and the crude product then reacted with an added phenol in a polar aprotic solvent system with microwave irradiation proved to be a useful simplification.