Total Syntheses and Anti-inflammatory Activities of Syringin and Its Natural Analogues

Syringin (1), a natural bioactive glucoside isolated from the root of Acanthopanax senticosus (Rupr. Maxim.) Harms, possesses significant anti-inflammatory activity. In this study, we have accomplished the total syntheses of syringin (1), along with its natural analogues 2-12, from a common starting material, syringaldehyde (13), in 4-8 steps with an overall yields of 11.8-61.3%. The anti-inflammatory activities of these compounds were determined against NO production in the LPS-stimulated RAW264.7 cells. Among them, compounds 1-5, 7, and 9 exhibited different levels of anti-inflammatory activity.

Concise Total Synthesis of Peyssonnoside A

Peyssonnoside A is a marine-derived sulfated diterpenoid glucoside with a unique 5/6/3/6 tetracyclic skeleton with a highly substituted cyclopropane ring deeply embedded into the structure. Herein, we report the first total synthesis of this natural product in a concise, efficient, scalable, and highly diastereoselective fashion. The aglucone peyssonnosol was synthesized in 21% overall yield after 15 steps, featuring a Simmons-Smith cyclopropanation and Mukaiyama hydration, fully controlled by the spatial structure of the substrates.

First Total Synthesis of Gaylussacin and Its Stilbene Derivatives

Gaylussacin (1), a stilbene glucoside, has been isolated from Pentarhizidium orientale and is used in Korean folk medicine. Although it was first isolated in 1972, the synthesis of gaylussacin has never been reported. Herein, we report the first total synthesis of gaylussacin in six steps with an overall yield of 23.8%, as well as the synthesis of its derivatives. Structurally, gaylussacin contains a carboxylic acid and a glycoside along with a free phenol on the same benzene ring, making selective functionalization for the synthesis of 1 difficult. Heck cross-coupling was employed as a key step to introduce the stilbene moiety. Glycosylation followed by global deprotection provided natural product 1.

Ab Initio Molecular Dynamics Simulations of the SN1/SN2 Mechanistic Continuum in Glycosylation Reactions

We report a computational approach to evaluate the reaction mechanisms of glycosylation using ab initio molecular dynamics (AIMD) simulations in explicit solvent. The reaction pathways are simulated via free energy calculations based on metadynamics and trajectory simulations using Born-Oppenheimer molecular dynamics. We applied this approach to investigate the mechanisms of the glycosylation of glucosyl α-trichloroacetimidate with three acceptors (EtOH, i-PrOH, and t-BuOH) in three solvents (ACN, DCM, and MTBE). The reactants and the solvents are treated explicitly using density functional theory. We show that the profile of the free energy surface, the synchronicity of the transition state structure, and the time gap between leaving group dissociation and nucleophile association can be used as three complementary indicators to describe the glycosylation mechanism within the SN1/SN2 continuum for a given reaction. This approach provides a reliable means to rationalize and predict reaction mechanisms and to estimate lifetimes of oxocarbenium intermediates and their dependence on the glycosyl donor, acceptor, and solvent environment.

Development of a deep-red fluorescent glucose-conjugated bioprobe for in vivo tumor targeting

A C1-type d-glucose-conjugated fluorescent probe Glu-1-O-DCSN was synthesized and showed deep-red emission at 685 nm with a Stokes shift of up to 150 nm in DMSO. In in vitro live cell imaging, Glu-1-O-DCSN exhibited similar and competitive uptake behaviours to d-glucose and was selectively located in mitochondria. Furthermore, Glu-1-O-DCSN was successfully employed for in vivo hypermetabolic tumor targeting.

Synthesis and Comparative Structure-Activity Study of Carbohydrate-Based Phenolic Compounds as α-Glucosidase Inhibitors and Antioxidants

Twenty-one natural and unnatural phenolic compounds containing a carbohydrate moiety were synthesized and their structure-activity relationship (SAR) was evaluated for α-glucosidase inhibition and antioxidative activity. Varying the position of the galloyl unit on the 1,5-anhydro-d-glucitol (1,5-AG) core resulted in changes in the α-glucosidase inhibitory activity and notably, particularly strong activity was demonstrated when the galloyl unit was present at the C-2 position. Furthermore, increasing the number of the galloyl units significantly affected the α-glucosidase inhibition, and 2,3,4,6-tetra-galloyl-1,5-AG (54) and 2,3,4,6-tetra-galloyl-d-glucopyranose (61) exhibited excellent activities, which were more than 13-fold higher than the α-glucosidase inhibitory activity of acertannin (37). Moreover, a comparative structure-activity study suggested that a hemiacetal hydroxyl functionality in the carbohydrate core and a biaryl bond of the 4,6-O-hexahydroxydiphenoyl (HHDP) group, which are components of ellagitannins including tellimagrandin I, are not necessary for the α-glucosidase inhibitory activity. Lastly, the antioxidant activity increased proportionally with the number of galloyl units.

Organocatalyzed preparation of 1,4,5-trisubstituted-glycosyl-1,2,3-triazole derivatives

Organocatalytic coupling of glycosyl azides with enolates of active ketones and esters through azide-enolate [3 + 2] cycloaddition in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) furnished 1,4,5-trisubstituted-glycosyl-1,2,3-triazole derivatives in excellent yield. The reaction condition is simple and can be scaled-up. Graphical abstract Coupling of glycosyl azides with active ketones through azide-enolate [3 + 2] cycloaddition in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) furnished 1,4,5-trisubstituted-glycosyl-1,2,3-triazole derivatives in excellent yield.

First Anti-ToCV Activity Evaluation of Glucopyranoside Derivatives Containing a Dithioacetal Moiety through a Novel ToCVCP-Oriented Screening Method

Tomato chlorosis virus (ToCV) is a newly reported plant virus that has rapidly spread to all parts of the world, resulting in a serious decline in tomato quality and yield due to the lack of effective control agents. In this study, the ToCV coat protein (ToCVCP) was expressed and purified in Escherichia coli, and a series of novel glucopyranoside derivatives containing a dithioacetal moiety was designed and synthesized. The binding affinity of these compounds to ToCVCP was determined using microscale thermophoresis. Results revealed that compounds 6b and 8a interacted with ToCVCP with K_d values of 0.12 and 0.21 μM, respectively. Quantitative reverse transcription polymerase chain reaction was used to evaluate the anti-ToCV activity of 6b and 8a in vivo, and both significantly reduced the expression level of ToCVCP gene in tomato compared with commercial antivirus agents. This study provides an efficient and convenient screening method for anti-ToCV agents and reliable support for the development of novel agrochemicals for ToCV.

Synthesis and Biological Evaluation of the Novel Growth Inhibitor Streptol Glucoside, Isolated from an Obligate Plant Symbiont

The plant Psychotria kirkii hosts an obligatory bacterial symbiont, Candidatus Burkholderia kirkii, in nodules on their leaves. Recently, a glucosylated derivative of (+)-streptol, (+)-streptol glucoside, was isolated from the nodulated leaves and was found to possess a plant growth inhibitory activity. To establish a structure-activity relationship study, a convergent strategy was developed to obtain several pseudosugars from a single synthetic precursor. Furthermore, the glucosylation of streptol was investigated in detail and conditions affording specifically the α or β glucosidic anomer were identified. Although (+)-streptol was the most active compound, its concentration in P. kirkii plant leaves extract was approximately ten-fold lower than that of (+)-streptol glucoside. These results provide compelling evidence that the glucosylation of (+)-streptol protects the plant host against the growth inhibitory effect of the compound, which might constitute a molecular cornerstone for this successful plant-bacteria symbiosis.

Investigation of the H-bond-mediated aglycone delivery reaction in application to the synthesis of β-glucosides

In an attempt to refine the H-bond-mediated Aglycone Delivery (HAD) glycosylation reaction reported herein is the synthesis of β-glucosides using an ethylthio glucoside donor equipped with the remote 6-O-picoloyl substituent. Upon examining various aliphatic, aromatic, and carbohydrate acceptors, it was determined that both electronic and steric factors may greatly affect the stereoselectivity of the HAD reaction with this donor.

Enzymatic synthesis of α-flavone glucoside via regioselective transglucosylation by amylosucrase from Deinococcus geothermalis

α-Flavone glycosides have beneficial properties for applications in the pharmaceutical, cosmetic, and food industries. However, their chemical syntheses are often limited by a low efficiency or scarcity of substrates. In this study, α-flavone glucosides were enzymatically synthesized by amylosucrase from Deinococcus geothermalis (DGAS) using sucrose and various flavones as a donor for glucosyl units and acceptors, respectively. Luteolin was the most effective acceptor in the transglucosylation reaction using DGAS among nine flavone materials (apigenin, chrysin, 6,7-dihydroxyflavone, homoorientin, 7-hydroxyflavone, isorhoifolin, luteolin, luteolin-3′,7-diglucoside, and orientin). The highest production yield of luteolin glucoside was 86%, with a 7:1 molar ratio of donor to acceptor molecules, in 50 mM Tris-HCl buffer (pH 7) at 37°C for 24 h using 2 U of DGAS. The synthesized luteolin glucoside was identified as luteolin-4′-O-α-D-glucopyranoside with a glucose molecule linked to the C-4′ position on the B-ring of luteolin via an α-glucosidic bond, as determined by ¹H and ¹³C nuclear magnetic resonance. This result clearly confirmed that the glucosylated luteolin was successfully synthesized by DGAS and it can be applied as a functional ingredient. Furthermore, this approach using DGAS has the potential to be utilized for the synthesis of various glucosylated products using different types of polyphenols to enhance their functionalities.

Monosaccharide inhibitors targeting carbohydrate esterase family 4 de-N-acetylases

The Carbohydrate Esterase family 4 contains virulence factors which modify peptidoglycan and biofilm-related exopolysaccharides. Despite the importance of this family of enzymes, a potent mechanism-based inhibition strategy has yet to emerge. Based on the postulated tridentate binding mode of the tetrahedral de-N-acetylation intermediate, GlcNAc derivatives bearing metal chelating groups at the 2 and 3 positions were synthesized. These scaffolds include 2-C phosphonate, 2-C sulfonamide, 2-thionoacetamide warheads as well as derivatives bearing thiol, amine and azide substitutions at the 3-position. The inhibitors were assayed against a representative peptidoglycan deacetylase, Pgda from Streptococcus pneumonia, and a representative biofilm-related exopolysaccharide deacetylase, PgaB from Escherichia coli. Of the inhibitors evaluated, the 3-thio derivatives showed weak to moderate inhibition of Pgda. The strongest inhibitor was benzyl 2,3-dideoxy-2-thionoacetamide-3-thio-β-d-glucoside, whose inhibitory potency showed an unexpected dependence on metal concentration and was found to have a partial mixed inhibition mode (K_i = 2.9 ± 0.6 μM).

Design, synthesis and biological evaluation of nitric oxide releasing derivatives of dapagliflozin as potential anti-diabetic and anti-thrombotic agents

The cardiovascular complications were highly prevalent in type 2 diabetes mellitus (T2DM), even at the early stage of T2DM or the state of intensive glycemic control. Therefore, there is an urgent need for the intervention of cardiovascular complications in T2DM. Herein, the new hybrids of NO donor and SGLT2 inhibitor were design to achieve dual effects of anti-hyperglycemic and anti-thrombosis. As expected, the preferred hybrid 2 exhibited moderate SGLT2 inhibitory effects and anti-platelet aggregation activities, and its anti-platelet effect mediated by NO was also confirmed in the presence of NO scavenger. Moreover, compound 2 revealed significantly hypoglycemic effects and excretion of urinary glucose during an oral glucose tolerance test in mice. Potent and multifunctional hybrid, such as compound 2, is expected as a potential candidate for the intervention of cardiovascular complications in T2DM.

Enzymatic Synthesis of a Novel Pterostilbene α-Glucoside by the Combination of Cyclodextrin Glucanotransferase and Amyloglucosidase

The synthesis of a novel α-glucosylated derivative of pterostilbene was performed by a transglycosylation reaction using starch as glucosyl donor, catalyzed by cyclodextrin glucanotransferase (CGTase) from Thermoanaerobacter sp. The reaction was carried out in a buffer containing 20% (v/v) DMSO to enhance the solubility of pterostilbene. Due to the formation of several polyglucosylated products with CGTase, the yield of monoglucoside was increased by the treatment with a recombinant amyloglucosidase (STA1) from Saccharomyces cerevisiae (var. diastaticus). This enzyme was not able to hydrolyze the linkage between the glucose and pterostilbene. The monoglucoside was isolated and characterized by combining ESI-MS and 2D-NMR methods. Pterostilbene α-d-glucopyranoside is a novel compound. The α-glucosylation of pterostilbene enhanced its solubility in water to approximately 0.1 g/L. The α-glucosylation caused a slight loss of antioxidant activity towards ABTS˙⁺ radicals. Pterostilbene α-d-glucopyranoside was less toxic than pterostilbene for human SH-S5Y5 neurons, MRC5 fibroblasts and HT-29 colon cancer cells, and similar for RAW 264.7 macrophages.

Potential Antitumor Activity of 2-O-α-d-Glucopyranosyl-6-O-(2-Pentylheptanoyl)-l-Ascorbic Acid

Intravenous administration of high-dose ascorbic acid (AA) has been reported as a treatment for cancer patients. However, cancer patients with renal failure cannot receive this therapy because high-dose AA infusion can have side effects. To solve this problem, we evaluated the antitumor activity of a lipophilic stable AA derivative, 2-O-α-d-glucopyranosyl-6-O-(2-pentylheptanoyl)-l-ascorbic acid (6-bOcta-AA-2G). Intravenous administration of 6-bOcta-AA-2G suppressed tumor growth in colon-26 tumor-bearing mice more strongly than did AA, even at 1/10 of the molar amount of AA. Experiments on the biodistribution and clearance of 6-bOcta-AA-2G and its metabolites in tumor-bearing mice showed that 6-bOcta-AA-2G was hydrolyzed to 6-O-(2-propylpentanoyl)-l-ascorbic acid (6-bOcta-AA) slowly to yield AA, and the results suggested that this characteristic metabolic pattern is responsible for making the antitumor activity of 6-bOcta-AA-2G stronger than that of AA and that the active form of 6-bOcta-AA-2G showing antitumor activity is 6-bOcta-AA. In in vitro experiments, the oxidized form of 6-bOcta-AA as well as 6-bOcta-AA showed significant cytotoxicity, while the oxidized forms of ascorbic acid showed no cytotoxicity at all, suggesting that the antitumor activity mechanism of 6-bOcta-AA-2G is different from that of AA and that the antitumor activity is due to the reduced and oxidized form of 6-bOcta-AA. The findings suggest that 6-bOcta-AA-2G is a potent candidate as an alternative drug to intravenous high-dose AA.

Stereospecific synthesis of methyl 2-amino-2-deoxy-(6S)-deuterio-α,β-d-glucopyranoside and methyl 2,6-diamino-2,6-dideoxy-(6R)-deuterio-α,β-d-glucopyranoside: Side chain conformations of the 2-amino-2-deoxy and 2,6-diamino-2,6-dideoxyglucopyranosides

The stereospecifically labeled 6-monodeuterio methyl 2,6-diamino-2,6-dideoxy-α- and β- d-glucopyranosides were synthesized with a view to determining their side chain conformations. NMR studies in D₂O at pH 5 and pH 11 reveal both anomers to adopt very predominantly the gt conformation consistent with the gauche conformation of 2-aminoethanol and its acetate salt. In contrast, as also revealed with the help of stereospecifically-labelled monodeuterio isotopomers, the methyl 2-amino-2-deoxy-α- and β- d-glucopyranosides are an approximately 1:1 mixture of gg and gt conformers as is found in glucopyranose itself.

A Sustainable One-Pot, Two-Enzyme Synthesis of Naturally Occurring Arylalkyl Glucosides

A sustainable, convenient, scalable, one-pot, two-enzyme method for the glucosylation of arylalkyl alcohols was developed. The reaction scheme is based on a transrutinosylation catalyzed by a rutinosidase from A. niger using the cheap commercially available natural flavonoid rutin as glycosyl donor, followed by selective "trimming" of the rutinoside unit catalyzed by a rhamnosidase from A. terreus. The process was validated with the syntheses of several natural bioactive glucosides, which could be isolated in up to 75 % yield without silica-gel chromatography.

S-Geranyl-2-thiouridine wobble nucleosides of bacterial tRNAs; chemical and enzymatic synthesis of S-geranylated-RNAs and their physicochemical characterization

Recently, highly lipophilic S-geranylated derivatives of 5-methylaminomethyl-2-thiouridine (mnm5geS2U) and 5-carboxymethylaminomethyl-2-thiouridine (cmnm5geS2U) were found at the first (wobble) anticodon position in bacterial tRNAs specific for Lys, Glu and Gln. The function and cellular biogenesis of these unique tRNAs remain poorly understood. Here, we present one direct and two post-synthetic chemical routes for preparing model geS2U-RNAs. Our experimental data demonstrate that geS2U-RNAs are more lipophilic than their parent S2U-RNAs as well as non-modified U-RNAs. Thermodynamic studies revealed that the S-geranyl-2-thiouridine-containing RNA has higher affinity toward complementary RNA strand with G opposite the modified unit than with A. Recombinant tRNA selenouridine synthase (SelU) exhibits sulfur-specific geranylation activity toward model S2U-RNA, which is composed of the anticodon-stem-loop (ASL) from the human tRNALys3 sequence. In addition, the presence of magnesium ions is required to achieve appreciable geranylation efficiencies.

Synthesis and Biological Evaluation of Iodoglucoazomycin (I-GAZ), an Azomycin-Glucose Adduct with Putative Applications in Diagnostic Imaging and Radiotherapy of Hypoxic Tumors

Iodoglucoazomycin (I-GAZ; N-(2-iodo-3-(6-O-glucosyl)propyl)-2-nitroimidazole), a non-glycosidic nitroimidazole-6-O-glucose adduct, was synthesized, radioiodinated, and evaluated as a substrate of glucose transporter 1 (GLUT1) for radiotheranostic (therapy+diagnostic) management of hypoxic tumors. Nucleophilic iodination of the nosylate synthon of I-GAZ followed by deprotection afforded I-GAZ in 74 % overall yield. I-GAZ was radioiodinated via 'exchange' labeling using [(123/131) I]iodide (50-70 % RCY) and then purified by Sep-Pak™ (>96 % RCP). [(131) I]I-GAZ was stable in 2 % ethanolic solution in sterile water for 14 days when stored at 5 °C. In cell culture, I-GAZ was found to be nontoxic to EMT-6 cells at concentrations <0.5 mm, and weakly radiosensitizing (SER 1.1 at 10 % survival of EMT-6 cells; 1.2 at 0.1 % survival in MCF-7 cells). The hypoxic/normoxic uptake ratio of [(123) I]I-GAZ in EMT-6 cells was 1.46 at 2 h, and under normoxic conditions the uptake of [(123) I]I-GAZ by EMT-6 cells was unaltered in the presence of 5 mm glucose. The biodistribution of [(131) I]I-GAZ in EMT-6 tumor-bearing Balb/c mice demonstrated rapid clearance from blood and extensive renal and hepatic excretion. Tumor/blood and tumor/muscle ratios reached ∼3 and 8, respectively, at 4 h post-injection. Regression analysis of the first order polynomial plots of the blood and tumor radioactivity concentrations supported a perfusion-excretion model with low hypoxia-dependent binding. [(131) I]I-GAZ was found to be stable in vivo, and did not deiodinate.

General and Stereocontrolled Approach to the Chemical Synthesis of Naturally Occurring Cyanogenic Glucosides

An effective method for the chemical synthesis of cyanogenic glucosides has been developed as demonstrated by the synthesis of dhurrin, taxiphyllin, prunasin, sambunigrin, heterodendrin, and epiheterodendrin. O-Trimethylsilylated cyanohydrins were prepared and subjected directly to glucosylation using a fully acetylated glucopyranosyl fluoride donor with boron trifluoride-diethyl etherate as promoter to afford a chromatographically separable epimeric mixture of the corresponding acetylated cyanogenic glucosides. The isolated epimers were deprotected using a triflic acid/MeOH/ion-exchange resin system without any epimerization of the cyanohydrin function. The method is stereocontrolled and provides an efficient approach to chemical synthesis of other naturally occurring cyanogenic glucosides including those with a more complex aglycone structure.

Mechanism of Glycosylation of Anomeric Sulfonium Ions

Anomeric sulfonium ions are attractive glycosyl donors for the stereoselective installation of 1,2-cis glycosides. Although these donors are receiving increasing attention, their mechanism of glycosylation remains controversial. We have investigated the reaction mechanism of glycosylation of a donor modified at C-2 with a (1S)-phenyl-2-(phenylsulfanyl)ethyl chiral auxiliary. Preactivation of this donor results in the formation of a bicyclic β-sulfonium ion that after addition of an alcohol undergoes 1,2-cis-glycosylation. To probe the importance of the thiophenyl moiety, analogs were prepared in which this moiety was replaced by an anisoyl or benzyl moiety. Furthermore, the auxiliaries were installed as S- and R-stereoisomers. It was found that the nature of the heteroatom and chirality of the auxiliary greatly influenced the anomeric outcome and only the one containing a thiophenyl moiety and having S-configuration gave consistently α-anomeric products. The sulfonium ions are sufficiently stable at a temperature at which glycosylations proceed indicating that they are viable glycosylation agents. Time-course NMR experiments with the latter donor showed that the initial rates of glycosylations increase with increases in acceptor concentration and the rate curves could be fitted to a second order rate equation. Collectively, these observations support a mechanism by which a sulfonium ion intermediate is formed as a trans-decalin ring system that can undergo glycosylation through a bimolecular mechanism. DFT calculations have provided further insight into the reaction path of glycosylation and indicate that initially a hydrogen-bonded complex is formed between sulfonium ion and acceptor that undergoes SN2-like glycosylation to give an α-anomeric product.

A new method testing the orthogonality of different protecting groups

A new test was elaborated to identify a new set of orthogonal protecting groups. With the developed method eight different protecting groups were tested under various deprotection conditions and the complex reaction mixtures were analysed by HPLC. The developed method allows for quick identification of orthogonality using simple model structures.

[SEARCHING FOR NEW SYNTHETIC DIURETICS]

This study was aimed at estimation of the diuretic and saluretic activity of 4-nitrophenyl-O-β-D-glucopyranoside and its aglicon 4-nitrophenol in rats. Test animals daily received 4-nitrophenyl-O-β-D-glucopyranoside (group 1) and 4-nitrophenol (group 2) intragastrically in 2 mL of distilled water in a dose of 18 µmol/kg from 1st to 7th day and 54 µmol/kg from 8th to 14th days. During the experiment, the most pronounced diuretic activity was observed for 4-nitrophenyl-O-β-D-glucopyranoside in a dose of 54 µmol/kg, which increased the diuresis in rats 2.5 times as compared to the control value.

Synthesis of the allelochemical alliarinoside present in garlic mustard (Alliaria petiolata), an invasive plant species in North America

The allelochemical alliarinoside present in garlic mustard (Alliaria petiolata), an invasive plant species in North America, was chemically synthesized using an efficient and practical synthetic strategy based on a simple reaction sequence. Commercially available 1,2,3,4,6-penta-O-acetyl-β-D-glucopyranose was converted into prop-2-enyl 2',3',4',6'-tetra-O-acetyl-β-D-glucopyranoside and subjected to epoxidation. In a one-pot reaction, ring-opening of the epoxide using TMSCN under solvent free conditions followed by treatment of the formed trimethylsilyloxy nitrile with pyridine and phosphoryl chloride, afforded the acetylated β-unsaturated nitriles (Z)-4-(2',3',4',6'-tetra-O-β-D-glucopyranosyloxy)but-2-enenitrile and its isomer (E)-4-(2',3',4',6'-tetra-O-β-D-glucopyranosyloxy)but-2-enenitrile. Deacetylation of Z- and/or E-isomers afforded the target molecules alliarinoside and its isomer.

Enzymatic Synthesis of 2-Chloro-4-nitrophenyl 4,6-O-3-Ketobutylideneβ-Maltopentaoside, a Substrate forα-Amylase

A transglycosylation reaction with 2-chloro-4-nitrophenyl beta-maltoside as an acceptor was done with 4,6-O-3-ketobutylidene maltopentaose and Bacillus macerans cyclodextrin glucanotransferase in an aqueous solution containing 50% n-propanol, and there were two main transglycosylation products. They were identified as 2-chloro-4-nitrophenyl 4,6-O-3-ketobutylidene beta-maltopentaoside and 2-chloro-4-nitrophenyl 4,6-O-3-ketobutylidene beta-maltohexaoside, and their yields were 30% and 21% respectively on the basis of the decrease of 4,6-O-3-ketobutylidene maltopentaose. For the production of 2-chloro-4-nitrophenyl 4,6-O-3-ketobutylidene beta-maltopentaoside at high substrates concentrations, the addition of n-propanol in this reaction not only increased the solubility of 2-chloro-4-nitrophenyl beta-maltoside sufficiently but also suppressed side reactions.

Synthesis of most polyene natural product motifs using just 12 building blocks and one coupling reaction

The inherent modularity of polypeptides, oligonucleotides and oligosaccharides has been harnessed to achieve generalized synthesis platforms. Importantly, like these other targets, most small-molecule natural products are biosynthesized via iterative coupling of bifunctional building blocks. This suggests that many small molecules also possess inherent modularity commensurate with systematic building block-based construction. Supporting this hypothesis, here we report that the polyene motifs found in >75% of all known polyene natural products can be synthesized using just 12 building blocks and one coupling reaction. Using the same general retrosynthetic algorithm and reaction conditions, this platform enabled both the synthesis of a wide range of polyene frameworks that covered all of this natural-product chemical space and the first total syntheses of the polyene natural products asnipyrone B, physarigin A and neurosporaxanthin b-D-glucopyranoside. Collectively, these results suggest the potential for a more generalized approach to making small molecules in the laboratory.

Enzymatic Synthesis of α-Anomer-SelectiveD-Glucosides Using Maltose Phosphorylase

A maltose phosphorylase (EC 2.4.1.8; MPase) showed novel acceptor specificity and transferred the glucosyl moiety of maltose not only to sugars but also to various acceptors having alcoholic OH groups. Salicyl alcohol acted as acceptor for MPase from Enterococcus hirae, and the product, salicyl-O-alpha-D-glucopyranoside (alpha-SalGlc) was identified. The yield based on supplied salicyl alcohol was 86% (mol/mol).

Characterization of Dimers of Hydroquinone Glucosides Produced by Peroxidase-Catalyzed Polymerization

4'-Hydroxyphenyl alpha-glucoside and 4'-hydroxyphenyl beta-glucoside were polymerized with horseradish peroxidase. The isolated dimers were found to have linkages at C3' of the hydroxyphenyl moieties and proved to be fluorescent. Low accumulation of oligomers was attributed to increasing electrochemical reactivity with polymerization degrees, which were expected from the levels of highest occupied molecular orbital.

[Research progress of alternative production approaches of salidroside]

Salidroside, one of the active components of Rhodiola plants, is a phenolic glycoside with significant biological activities. The investigation and development of alternative production approaches of salidroside is of high academic and application values due to the limited resource of Rhodiola plants, and from which the low yield of salidroside. This review summarized the research progress and perspective of the alternative production approaches of salidroside including both chemosynthetic and biosynthetic methods and pathways.

A novel type of highly effective nonionic gemini alkyl O-glucoside surfactants: a versatile strategy of design

A novel type of highly effective gemini alkyl glucosides has been rationally designed and synthesized. The gemini surfactants have been readily prepared by glycosylation of the gemini alkyl chains that are synthesized with regioselective ring-opening of ethylene glycol epoxides by the alkyl alcohols. The new gemini alkyl glucosides exhibit significantly better surface activity than the known results. Then rheological, DLS, and TEM studies have revealed the intriguing self-assembly behavior of the novel gemini surfactants. This study has proved the effectiveness of the design of gemini alkyl glucosides which is modular, extendable, and synthetically simple. The new gemini surfactants have great potential as nano carriers in drug and gene delivery.

Antidiabetic effect of secoisolariciresinol diglucoside in streptozotocin-induced diabetic rats

Diabetes mellitus is a chronic metabolic disorder characterized by hyperglycaemia. Its complications such as neuropathy, cardiopathy, nephropathy, and micro and macro vascular diseases are believed to be due to the increase in oxidative stress and decrease in the level of antioxidants. The aim of this study was to determine the antihyperglycemic activity of synthetic Secoisolariciresinol diglucoside (SDG) in streptozotocin (STZ)-induced diabetic rats. The synthetic SDG in a single-dose (20 mg/kg b.w.) two-day study showed dose-dependent reduction in glucose levels with maximum effect of 64.62% at 48 h post drug treatment (p<0.05), which is comparable to that of the standard drug tolbutamide (20 mg/kg b.w.). In a multi-dose fourteen-day study, lower doses of SDG (5 and 10 mg/kg b.w.) exhibited moderate reduction in glucose levels, lipid profile, restoration of antioxidant enzymes and improvement of the insulin and c-peptide levels which shows the regeneration of β-cell which secretes insulin. Altered levels of lipids and enzymatic antioxidants were also restored by the SDG to the considerable levels in diabetic rats. Results of the present investigation suggest that diabetes is associated with an increase in oxidative stress as shown by increase in serum malondialdehyde (MDA), decreased levels of catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH). Also, diabetes is associated with an increase in serum total cholesterol as well as triglycerides levels and decrease in insulin and c-peptide levels. SDG is effective in retarding the development of diabetic complications. We propose that synthetic SDG exerts anti hyperglycemic effect by preventing the liver from peroxidation damage through inhibition of ROS level mediated increased level of enzymatic and non-enzymatic antioxidants. And, also maintaining tissue function which results in improving the sensitivity and response of target cells in STZ-induced diabetic rats to insulin.

Synthesis of 3,5,3',4'-tetrahydroxy-trans-stilbene-4'-O-beta-D-glucopyranoside by glucosyltransferases from Phytolacca americana

Two glucosyltransferase isozymes from Phytolacca americana, PaGT3 and PaGT2, catalyzed stereo- and regio-selective monoglucosylation of 3,5,3',4'-tetrahydroxy-trans-stilbene to yield 3,5,3',4'-tetrahydroxy-trans-stilbene-4'-O-beta-D-glucopyranoside.

Synthesis, isolation, structure elucidation, and color properties of 10-acetyl-pyranoanthocyanins

Grape anthocyanins reacted with diacetyl, a secondary metabolite of microorganisms involved in winemaking, to form 10-acetyl-pyranoanthocyanins, a type of anthocyanin-derived pigment similar to other vitisin-type pyranoanthocyanins found in red wines. The structures of 10-acetyl-pyranomalvidin-3-β-O-glucoside and 10-acetyl-pyranopeonidin-3-β-O-glucoside were confirmed by spectroscopic methods (UV-vis, MS/MS, and NMR) after their synthesis and isolation. In contrast to other vitisin-type pyranoanthocyanins, the newly described 10-acetyl-pyranoanthocyanins exhibited differentiated color-related properties. They showed an important tendency to occur as colorless hemiacetals at C-10 under wine pH conditions, while co-occurrence of flavylium cation and quinoidal base yielded a broad visible absorbance band around 510-520 nm. Moreover, they easily reacted with bisulfite in acidic aqueous solution (pH 2.0), but the expected bleaching was not observed. Bisulfite bonded to the carbonyl of 10-acetyl substituent instead of the expected C-10 position of the pyranoanthocyanin core, thus giving rise to a red pigment hypsochromically shifted toward orangish nuances (maximum absorbances at 487-491 nm).

2,2,2-Trifluoroethyl 6-thio-β-D-glucopyranoside as a selective tag for cysteines in proteins

A synthetic route to a trifluoromethyl and thiol containing glucose derivative (2,2,2-trifluoroethyl 6-thio-β-d-glucopyranoside) is presented, which is based on microwave-assisted Fischer glycosylation under increased pressure. This water-soluble, neutral thiol-compound can be used to selectively introduce a fluorine probe for ¹⁹F NMR spectroscopy on cysteines in proteins. It can be attached under mild conditions in an aqueous environment without the risk of denaturing the protein. This tag has been applied to determine the redox-state of two cysteine residues in a bacterial transcription activator. Qualitative information about the solvent accessibility can be obtained from F-19 solvent PREs.

[Research progress of sodium-glucose co-transporter 2 inhibitors for treatment of type 2 diabetes]

Sodium-glucose co-transporters are a family of glucose transporter found in the intestinal mucosa of the small intestine (SGLT-2) and the proximal tubule of the nephron (SGLT-1 and SGLT-2). They contribute to renal glucose reabsorption and most of renal glucose (about 90%) is reabsorbed by SGLT-2 located in the proximal renal tubule. Selectively inhibiting activity of SGLT-2 is an innovative therapeutic strategy for treatment of type 2 diabetes by enhancing urinary glucose excretion from the body. Therefore SGLT-2 inhibitors are considered to be potential antidiabetic drugs with an unique mechanism. This review will highlight some recent advances and structure-activity relationships in the discovery and development of SGLT-2 inhibitors including O-glycoside, C-glycoside, C, O-spiro glycoside and non glycosides.

Highly efficient synthesis and antitumor activity of monosaccharide saponins mimicking components of Chinese folk medicine Cordyceps sinensis

Ergosterol 3-O-β-D-glucopyranoside (1a) and ergosterol 3-O-β-D-galactopyranoside (1b) were highly efficiently synthesized and evaluated for their inhibitory activities against two tumor cell lines. The structures of these compounds were extensively confirmed by (1)H, (13)C NMR, IR, and HRMS. Compounds 1a and 1b exhibited interesting cytotoxic profiles. The antitumor activity of compound 1a was higher than that of 1b.

Synthesis of glucose-fipronil conjugate and its phloem mobility

Phloem-mobile insecticides are preferred to achieve economically useful activity. However, only a few phloem-mobile synthetic insecticides are available. One approach to converting nonmobile insecticides into phloem-mobile types is introducing sugar to the parent compound. To test whether the addition of a glucose group to a non-phloem-mobile insecticide enables conversion into phloem-mobile, N-[3-cyano-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazol-5-yl]-1-(β-D-glucopyranosyl)-1H-1,2,3-triazole-4-methanamine (GTF) was prepared through click chemistry. A phloem-mobility test in Ricinus communis L. seedlings confirmed that GTF was mobile in the sieve tubes. Although GTF exhibited lower insecticidal activity against the third-instar larvae of Pzlutella xylostella than fipronil did, it can be reconverted into fipronil in adult plants of castor bean, thereby offsetting the decrease of insecticidal activity. Therefore, the presence of a glucose core confers phloem mobility to fipronil.

A gram scale synthesis of a multi-13C-labelled anthocyanin, [6,8,10,3',5'-13C5]cyanidin-3-glucoside, for use in oral tracer studies in humans

The major dietary anthocyanin, cyanidin-3-glucoside, was prepared on a 4 g scale from three units of diethyl [2-(13)C]malonate and one unit of [1,3-(13)C(2)]acetone, such that five isotope locations were distributed throughout the molecule to provide a penta-(13)C(5)-labelled anthocyanin, [6,8,10,3',5'-(13)C(5)]cyanidin-3-glucoside chloride, for use in human stable-isotope tracer studies.

Thermo-kinetics of lipase-catalyzed synthesis of 6-O-glucosyldecanoate

Lipase-catalyzed synthesis of 6-O-glucosyldecanoate from d-glucose and decanoic acid was performed in dimethyl sulfoxide (DMSO), a mixture of DMSO and tert-butanol and tert-butanol alone with a decreasing order of polarity. The highest conversion yield (> 65%) of decanoic acid was obtained in the blended solvent of intermediate polarity mainly because it could dissolve relatively large amounts of both the reactants. The reaction obeyed Michaelis-Menten type of kinetics. The affinity of the enzyme towards the limiting substrate (decanoic acid) was not affected by the polarity of the solvent, but increased significantly with temperature. The esterification reaction was endothermic with activation energy in the range of 60-67 kJ mol⁻¹. Based on the Gibbs energy values, in the solvent blend of DMSO and tert-butanol the position of the equilibrium was shifted more towards the products compared to the position in pure solvents. Monoester of glucose was the main product of the reaction.

Asymmetric enzymatic glycosylation of mitoxantrone

Using a uniquely promiscuous engineered glycosyltransferase (GT) derived from the macrolide-inactivating GT OleD, a single-step asymmetric glucosylation of one 'arm' of the drug mitoxantrone was efficiently achieved in high stereo- and regiospecificity. The synthesis, structural elucidation, and anticancer activity of the corresponding mitoxantrone 4'-β-D-glucoside are described.

Glycosylated nordihydroguaiaretic acids as anti-cancer agents

Three perglycosylated nordihydroguaiaretic acids (NDGA) were synthesized through the Huiseng 1,3-dipolar cycloaddition reaction. These sugar-NDGA conjugates containing triazole-linkages possessed good solubility in water. NDGA-(triazol-galactose)(4) (12b) and NDGA-(triazol-glucose)(4) (12c) were found to act as inhibitors against human hepatocellular carcinoma Hep3B cells in culture.

Synthesis of vicenin-1 and 3, 6,8- and 8,6-di-C-beta-D-(glucopyranosyl-xylopyranosyl)-4',5,7-trihydroxyflavones using two direct C-glycosylations of naringenin and phloroacetophenone with unprotected D-glucose and D-xylose in aqueous solution as the key reactions

Vicenin-3 was synthesized from naringenin via a short five-step reaction, which included two regioselective direct C-glycosylations with d-glucose and d-xylose (yields: 22% and 30%, respectively) as the key reactions for a total yield of 4.4%. Vicenin-1 was also synthesized from phloroacetophenone via a 10-step reaction, including the same glycosylation described above, for a total yield of 2.7% with a vicenin-3 yield of 1.7%.

Tuning the helicity of self-assembled structure of a sugar-based organogelator by the proper choice of cooling rate

A novel sugar-appended low-molecular-mass gelator, 4''-butoxy-4-hydroxy-p-terphenyl-beta-D-glucoside (BHTG), was synthesized. It formed thermally reversible gels in a variety of aqueous and organic solvents. Three-dimensional networks made up of helical ribbons were observed in the mixture of H(2)O/1,4-dioxane (40/60 v/v). The handedness of the ribbons depended on the rate of gel formation. Fast-cooling process led to right-handed ribbons, while slow-cooling process led to left-handed ones. A combinatory analyses of microscopic, spectroscopic, and diffraction techniques revealed that BHTG formed a twisted interdigitated bilayer structure with a d spacing of 3.1 nm in gels through a kinetically controlled nucleation-growth process. There were two kinds of molecular orientations of BHTG in the nuclei, clockwise and anticlockwise, which dictated the growth of ribbons. One was metastable and formed first during the cooling process of gel formation. It was able to gradually transform into the more stable latter one with further decreasing temperature. Fast-cooling process did not leave enough time for the nuclei to evolve from metastable to stable state and the ribbons grown from them exhibited right-handedness. However, the metastable nuclei transformed into the stable one when cooled slowly and directed the molecules of BHTG to grow into left-handed aggregates.

Total synthesis of adicardin

The first synthesis of adicardin, a compound with anti-chronic renal failure activity isolated from Hydrangea macrophylla, has been described. The structures of the target compound and intermediates have been validated by MS, NMR, and identical with the natural product.

Absorption of 3(2H)-furanones by human intestinal epithelial Caco-2 cells

A number of 3(2H)-furanones are synthesized by fruits and have been found in cooked foodstuffs, where they impart flavor and odor because of their low perception thresholds. They show genotoxic properties in model studies but are also ranked among the antioxidants and anticarcinogens. This study examined the efficiency of intestinal absorption and metabolic conversion of 3(2H)-furanones by using Caco-2 cell monolayers as an intestinal epithelial cell model. The permeability of each agent was measured in both the apical to basal and basal to apical directions. 2,5-Dimethyl-4-methoxy-3(2H)-furanone (DMMF) showed the highest absorption rate in all experiments, while similar amounts of 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF), 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF), and 4-hydroxy-5-methyl-3(2H)-furanone (HMF) were taken up. HDMF-glucoside was almost not absorbed but was hydrolyzed to a small extent. The transport of 3(2H)-furanones could not be saturated even at levels of 500 microM and occurred in both directions. Because the uptake was only slightly reduced by apical hyperosmolarity, passive diffusion by paracellular transport is proposed.

Dimethylthexylsilyl 2-acetamido-3-O-allyl-2-deoxy-6-O-(4-methoxybenzyl)-beta-D-glucopyranoside, dimethylthexylsilyl 3,4,6-tri-O-benzyl-beta-D-mannopyranosyl-(1-->4)-2-acetamido-3-O-allyl-2-deoxy-6-O-(4-methoxybenzyl)-beta-D-glucopyranoside, and dimethylthexylsilyl 2-O-(benzylsulfonyl)-3,4,6-tri-O-benzyl-beta-D-mannopyranosyl-(1-->4)-2-acetamido-3-O-allyl-2-deoxy-6-O-(4-methoxybenzyl)-beta-D-glucopyranoside: synthesis of authentic samples

Dimethylthexylsilyl 2-acetamido-3-O-allyl-2-deoxy-6-O-(4-methoxybenzyl)-beta-D-glucopyranoside was prepared by reduction of the corresponding 4,6-O-(4-methoxybenzylidene) acetal with sodium cyanoborohydride and trifluoroacetic acid. This alcohol was coupled to 2-O-benzoyl-3,4,6-tri-O-benzyl-alpha-D-glucopyranosyl trichloroacetimidate to give a beta-glucoside that was converted to dimethylthexylsilyl 3,4,6-tri-O-benzyl-beta-D-mannopyranosyl-(1-->4)-2-acetamido-3-O-allyl-2-deoxy-6-O-(4-methoxybenzyl)-beta-D-glucopyranoside by saponification, Dess-Martin oxidation, and sodium borohydride reduction. Sulfonylation then gave dimethylthexylsilyl 2-O-(benzylsulfonyl)-3,4,6-tri-O-benzyl-beta-D-mannopyranosyl-(1-->4)-2-acetamido-3-O-allyl-2-deoxy-6-O-(4-methoxybenzyl)-beta-D-glucopyranoside.

Role of vinylcatechin in the formation of pyranomalvidin-3-glucoside-+-catechin

Reactions between malvidin-3-glucoside (mv3glc) and 8-vinylcatechin were carried out to synthesize pyranomv3glc-(+)-catechin pigment and to study the formation of intermediates. A rapid decrease of mv3glc content concomitant with the formation of more complex structures such as mv3glc-vinylcatechin [precursor of pyranomv3glc-(+)-catechin pigment] and mv3glc-divinylcatechin was observed. On the other hand, 8-vinylcatechin undergoes acid-catalyzed dimerization in model wine solution, giving rise to 8-vinylcatechin dimers. These compounds were also found in the reaction between mv3glc and (+)-catechin mediated by acetaldehyde, which provides evidence for the formation of 8-vinylcatechin and its involvement in the formation of pyranoanthocyanins in aged red wines.

Structure elucidation and NMR spectral assignments of three new lignan glycosides from Akebia trifoliata

Three new lignan glycosides (1-3) were isolated from the stems of Akebia trifoliata. Their structures were elucidated as (7R,8R,7'R,8'R)3,3',5,5'tetramethoxy-4,4'dihydroxy-7,9':7',9-diepoxylignan-4-O-beta-D-glucopyranoside (1), (7S,8S,8'R)-4,4',9-trihydroxy-3,3',5,5'-tetramethoxy-7,9'-epoxylignan-7'-one 9-O-beta-D-glucopyranoside (2), (7R,8R,8'S)-4,4',9-trihydroxy3,3',5,5'-tetramethoxy-7,9'-epoxylignan-7'-one 9-O-beta-D-glucopyranoside (3) by spectral analyses, primarily NMR, MS and CD. The NMR assignments for the compounds were carried out using 1H, 13C, DEPT, COSY, HSQC, HMBC and ROESY NMR experiments.