FeCl3-promoted and ultrasound-assisted synthesis of resveratrol O-derived glycoside analogs

Ferric Chloride Promoted Glycosidation of Alkyl Thioglycosides

Reported herein is a new reaction for glycosylation with thioglycosides in the presence of iron(III) chloride. Previously, FeCl3 was used for the activation of thioglycosides as a Lewis acid co-promoter paired with NIS. In the reported process, although 5.0 equiv of FeCl3 are needed to activate thioglycosides most efficiently, no additives were used, and the reactions with reactive glycosyl donors smoothly proceeded to completion in 1 h at 0 °C. This work showcases a new direction in developing glycosylation methods using greener and earth-abundant activators.

Synthesis and Characterization of a Novel Resveratrol Xylobioside Obtained Using a Mutagenic Variant of a GH10 Endoxylanase

Resveratrol is a natural polyphenol with antioxidant activity and numerous health benefits. However, in vivo application of this compound is still a challenge due to its poor aqueous solubility and rapid metabolism, which leads to an extremely low bioavailability in the target tissues. In this work, rXynSOS-E236G glycosynthase, designed from a GH10 endoxylanase of the fungus Talaromyces amestolkiae, was used to glycosylate resveratrol by using xylobiosyl-fluoride as a sugar donor. The major product from this reaction was identified by NMR as 3-O-ꞵ-d-xylobiosyl resveratrol, together with other glycosides produced in a lower amount as 4'-O-ꞵ-d-xylobiosyl resveratrol and 3-O-ꞵ-d-xylotetraosyl resveratrol. The application of response surface methodology made it possible to optimize the reaction, producing 35% of 3-O-ꞵ-d-xylobiosyl resveratrol. Since other minor glycosides are obtained in addition to this compound, the transformation of the phenolic substrate amounted to 70%. Xylobiosylation decreased the antioxidant capacity of resveratrol by 2.21-fold, but, in return, produced a staggering 4,866-fold improvement in solubility, facilitating the delivery of large amounts of the molecule and its transit to the colon. A preliminary study has also shown that the colonic microbiota is capable of releasing resveratrol from 3-O-ꞵ-d-xylobiosyl resveratrol. These results support the potential of mutagenic variants of glycosyl hydrolases to synthesize highly soluble resveratrol glycosides, which could, in turn, improve the bioavailability and bioactive properties of this polyphenol.

Ultrasound-Accelerated, Concise, and Highly Efficient Synthesis of 2-Oxazoline Derivatives Using Heterogenous Calcium Ferrite Nanoparticles and Their DFT Studies

A rapid and operationally simple approach for synthesising biologically relevant 2-oxazoline derivatives has been developed through highly efficient ultrasound-promoted coupling reactions of thioamides and amino alcohols using calcium ferrite nanoparticles as heterogeneous catalysts. The major advantage of using ultrasound irradiation lies in the drastic reduction of reaction time as compared with conventional stirring. Furthermore, quantum chemical investigations for the synthesised 2-oxazoline derivatives have been carried out at the DFT/B3LYP/6-311 + G (d, p) level of theory to predict the optimized geometry. The molecular properties such as bond lengths, bond orders, Milliken charges, frontier molecular orbitals, global reactivity descriptors, molecular electrostatic potential map, and thermodynamic parameters of all the compounds have also been reported at the same level of theory.

Thiazolidinediones: An In-Depth Study of Their Synthesis and Application to Medicinal Chemistry in the Treatment of Diabetes Mellitus

2,4-Thiazolidinedione (TZD) is a privileged and highly utilised scaffold for the development of pharmaceutically active compounds. This sulfur-containing heterocycle is a versatile pharmacophore that confers a diverse range of pharmacological activities. TZD has been shown to exhibit biological action towards a vast range of targets interesting to medicinal chemists. In this review, we attempt to provide insight into both the historical conventional and the use of novel methodologies to synthesise the TZD core framework. Further to this, synthetic procedures utilised to substitute the TZD molecule at the activated methylene C5 and N3 position are reviewed. Finally, research into developing clinical agents, which act as modulators of peroxisome proliferator-activated receptors gamma (PPARγ), protein tyrosine phosphatase 1B (PTP1B) and aldose reductase 2 (ALR2), are discussed. These are the three most targeted receptors for the treatment of diabetes mellitus (DM).

Ultrasound-assisted one-pot green synthesis of new N- substituted-5-arylidene-thiazolidine-2,4-dione-isoxazoline derivatives using NaCl/Oxone/Na3PO4 in aqueous media

A rapid and green method for the synthesis of novel N-thiazolidine-2,4-dione isoxazoline derivatives 5 from N-allyl-5-arylidenethiazolidine-2,4-diones 3 as dipolarophiles with arylnitrile oxides via 1,3-dipolar cycloaddition reaction. The corresponding N-allyl substituted dipolarophiles were prepared by one-pot method from thiazolidine-2,4-dione with aldehydes using Knoevenagel condensation followed by N-allylation of thiazolidine-2,4-dione in NaOH aqueous solution under sonication. In addition, the isoxazoline derivatives 5 were synthesized by regioselective and chemoselective 1,3-dipolar cycloaddition using inexpensive and mild NaCl/Oxone/Na₃PO₄ as a Cl source, oxidant and/or catalyst under ultrasonic irradiation in EtOH/H₂O (v/v, 2:1) as green solvent. All synthesized products are furnished in good yields in the short reaction time, and then their structures were confirmed by NMR, mass spectrometry and X-ray crystallography analysis.

A straightforward and versatile FeCl3 catalyzed Friedel–Crafts C-glycosylation process. Application to the synthesis of new functionalized C-nucleosides

Rapid and straightforward access to C-nucleosides using an inexpensive FeCl₃ catalyst.

Iron(iii) chloride-catalyzed activation of glycosyl chlorides

Glycosyl chlorides have historically been activated using harsh conditions and/or toxic stoichiometric promoters. More recently, the Ye and the Jacobsen groups showed that glycosyl chlorides can be activated under organocatalytic conditions. However, those reactions are slow, require specialized catalysts and high temperatures, but still provide only moderate yields. Presented herein is a simple method for the activation of glycosyl chlorides using abundant and inexpensive ferric chloride in catalytic amounts. Our preliminary results indicate that both benzylated and benzoylated glycosyl chlorides can be activated with 20 mol% of FeCl3.

Modular synthesis of new C-aryl-nucleosides and their anti-CML activity

The C-aryl-ribosyles are of utmost interest for the development of antiviral and anticancer agents. Even if several synthetic pathways have been disclosed for the preparation of these nucleosides, a direct, few steps and modular approaches are still lacking. In line with our previous efforts, we report herein a one step - eco-friendly β-ribosylation of aryles and heteroaryles through a direct Friedel-Craft ribosylation mediated by bismuth triflate, Bi(OTf)₃. The resulting carbohydrates have been functionalized by cross-coupling reactions, leading to a series of new C-aryl-nucleosides (32 compounds). Among them, we observed that 5d exerts promising anti-proliferative effects against two human Chronic Myeloid Leukemia (CML) cell lines, both sensitive (K562-S) or resistant (K562-R) to imatinib, the "gold standard of care" used in this pathology. Moreover, we demonstrated that 5d kills CML cells by a non-conventional mechanism of cell death.

Ultrasound-assisted facile one-pot sequential synthesis of novel sulfonamide-isoxazoles using cerium (IV) ammonium nitrate (CAN) as an efficient oxidant in aqueous medium

A series of novel 3,5-disubstituted isoxazoles have been synthesized, using a new, green, and versatile "one-pot three-steps" methodology. The key step is an oxidative 1,3-dipolar cycloaddition under ultrasonic irradiation, occurring in aqueous media, and mediated by cerium (IV) ammonium nitrate (CAN). CAN is a one-electron oxidant, highly soluble in water, slightly toxic and inexpensive, that allows the in situ conversion of the intermediate aldoximes into nitrile oxide. The syntheses are highly regioselective, as illustrated by the structures of the final compounds, which have been fully assessed by spectral analyses (¹H and ¹³C NMR, MS). This study illustrates the potency of the ultrasound activation to synthesize a set of highly functionalized heterocycles, with potential applications in biology, in short reaction times and following an eco-friendly process.

Structure activity relationship and optimization of N-(3-(2-aminothiazol-4-yl)aryl)benzenesulfonamides as anti-cancer compounds against sensitive and resistant cells

We recently described a new family of bioactive molecules with interesting anti-cancer activities: the N-(4-(3-aminophenyl)thiazol-2-yl)acetamides. The lead compound of the series (1) displays significant anti-proliferative and cytotoxic activities against a panel of cancer cell lines, either sensitive or resistant to standard treatments. This molecule also shows a good pharmacological profile and high in vivo potency towards mice xenografts, without signs of toxicity on the animals. In the present article, we disclose the structure-activity relationships of this lead compound, which have provided clear information about the replacement of the acetamide function and the substitution pattern of the benzenesulfonamide ring. An improved high-yielding synthetic procedure towards these compounds has also been developed. Our drug design resulted in potency enhancement of 1, our new optimized lead compound being 19. These findings are of great interest to further improve this scaffold for the development of future clinical candidates.

Synthesis and anti-cancer activities of new sulfonamides 4-substituted-triazolyl nucleosides

Nucleoside analogues are among the most known drugs commonly used in antiviral and anticancer chemotherapies. Among them, those featuring a five-membered ring nucleobase are of utmost interest such as the anti-cancer agent AICAR or the anti-viral drug ribavirin. Despite its low activity in vitro in different cell lines, AICAR is under clinical development for several pathologies, thanks to its original mode of action. Indeed, AICAR induced autophagy cell death and is able, following this mechanism, to circumvent resistance to apoptotic drugs including kinase inhibitors currently on the market. To improve the activity of AICAR, we report herein an efficient synthesis of new series of sulfonamide-4-substituted-1,2,3-triazolyl nucleosides using a Cu-catalyzed 1,3-dipolar cycloaddition. All these molecules have been fully characterized and evaluated against two aggressive tumor cell lines, RCC4 and MDA-MB-231. Among them, nucleoside analogue 5i belonging to the ribose series was found to be 19 to 66-fold more active than AICAR. Western blot analyses on RCC4 cells showed that 5i displayed an interesting mode of action by inducing both apoptosis and autophagy cell death, making therefore this class of molecules highly promising for further hit-to-lead optimization.

Efficient and selective azidation of per-O-acetylated sugars using ultrasound activation: application to the one-pot synthesis of 1,2,3-triazole glycosides

A new protocol was developed for the selective transformation of acetyl-sugars to triazolyl nucleosides using in situ generated SO₂(N₃)₂, iron/copper cocatalysis and ultrasound activation.