The effect of the beta-D-xyloside naroparcil on circulating plasma glycosaminoglycans. An explanation for its known antithrombotic activity in the rabbit

Molecular Mechanisms in Pathophysiology of Mucopolysaccharidosis and Prospects for Innovative Therapy

Mucopolysaccharidoses (MPSs) are a group of inborn errors of the metabolism caused by a deficiency in the lysosomal enzymes required to break down molecules called glycosaminoglycans (GAGs). These GAGs accumulate over time in various tissues and disrupt multiple biological systems, including catabolism of other substances, autophagy, and mitochondrial function. These pathological changes ultimately increase oxidative stress and activate innate immunity and inflammation. We have described the pathophysiology of MPS and activated inflammation in this paper, starting with accumulating the primary storage materials, GAGs. At the initial stage of GAG accumulation, affected tissues/cells are reversibly affected but progress irreversibly to: (1) disruption of substrate degradation with pathogenic changes in lysosomal function, (2) cellular dysfunction, secondary/tertiary accumulation (toxins such as GM2 or GM3 ganglioside, etc.), and inflammatory process, and (3) progressive tissue/organ damage and cell death (e.g., skeletal dysplasia, CNS impairment, etc.). For current and future treatment, several potential treatments for MPS that can penetrate the blood-brain barrier and bone have been proposed and/or are in clinical trials, including targeting peptides and molecular Trojan horses such as monoclonal antibodies attached to enzymes via receptor-mediated transport. Gene therapy trials with AAV, ex vivo LV, and Sleeping Beauty transposon system for MPS are proposed and/or underway as innovative therapeutic options. In addition, possible immunomodulatory reagents that can suppress MPS symptoms have been summarized in this review.

Intimal Hyperplasia of Arteriovenous Fistula

Intimal hyperplasia (IH), a crucial histopathological injury, forms the basis of vascular stenosis and thrombogenesis. In addition, it is common in maladies such as stenosis at the anastomosis of arteriovenous fistula and restenosis after angioplasty. Various cellular and noncellular components play critical parts in the advancement of IH. This article reviews the distinctive components of IH, such as endothelial dysfunction, multiplication, and movement of vascular smooth muscle cells. Finally, in addition to synthesis of large amounts of extracellular matrix and inflammatory responses, which have frequently been studied in recent years, we offer a premise for clinical treatment with vascular smooth muscle cells.

Azide-Functionalized Naphthoxyloside as a Tool for Glycosaminoglycan Investigations

We present a xylosylated naphthoxyloside carrying a terminal azide functionality that can be used for conjugation using click chemistry. We show that this naphthoxyloside serves as a substrate for β4GalT7 and induces the formation of soluble glycosaminoglycan (GAG) chains with physiologically relevant lengths and sulfation patterns. Finally, we demonstrate its usefulness by conjugation to the Alexa Fluor 647 and TAMRA fluorophores and coupling to a surface plasmon resonance chip for interaction studies with the hepatocyte growth factor known to interact with the GAG heparan sulfate.

Palladium-Catalyzed ortho-C(sp2)-H Silylation of Aromatic Ketones Using an Aminooxyamide Auxiliary

A palladium-catalyzed direct and selective ortho-C(sp²)-H silylation of aromatic ketones has been achieved using an aminooxyamide auxiliary. The reaction tolerates various orth-, meta-, and para- substituents on the aromatic ring and can be applied to thiophenyl and vinyl ketones. The ortho-C(sp²)-H bond was monosilylated selectively in comparison with other aromatic C-H bonds, benzyl or allylic C(sp³)-H bonds, and acidic α-C(sp³)-H bonds. The aminooxyamide auxiliary can be easily installed and readily removed after the silylation reaction. The resulting ortho-silyl aromatic ketone derivatives are potentially useful building blocks for organic synthesis.

Visible-Light-Driven Selective Air-Oxygenation of C-H Bond via CeCl3 Catalysis in Water

Visible-light-induced C-H aerobic oxidation is an important chemical transformation that can be applied for the synthesis of aromatic ketones. High-cost catalysts and toxic solvents were generally needed in the present methodologies. Here, an efficient aqueous C-H aerobic oxidation protocol was reported. Through CeCl₃ -mediated photocatalysis, a series of aromatic ketones were produced in moderate to excellent yields. With air as the oxidant, this reaction could be performed under mild conditions in water and demonstrated high activity and functional group tolerance. This method is economical, highly efficient, and environmentally friendly, and it will provide inspiration for the development of aqueous photochemical synthesis reactions.

Pd-Catalysed direct C(sp2)-H fluorination of aromatic ketones: concise access to anacetrapib

The Pd-cataylsed direct ortho-C(sp2)-H fluorination of aromatic ketones has been developed for the first time. The reaction features good regioselectivity and simple operations, constituting an alternative shortcut to access fluorinated ketones. A concise synthesis of anacetrapib has also been achieved by using late-stage C-H fluorination as a key step.

Merging CF3SO2Na photocatalysis with palladium catalysis to enable decarboxylative cross-coupling for the synthesis of aromatic ketones at room temperature

By merging CF₃SO₂Na-mediated photocatalysis with palladium catalysis, an efficient decarboxylative coupling strategy of α-keto acids and aryl boronic acids has been developed for the synthesis of aromatic ketones.

Odiparcil, a potential glycosaminoglycans clearance therapy in mucopolysaccharidosis VI-Evidence from in vitro and in vivo models

Mucopolysaccharidoses are a class of lysosomal storage diseases, characterized by enzymatic deficiency in the degradation of specific glycosaminoglycans (GAG). Pathological accumulation of excess GAG leads to multiple clinical symptoms with systemic character, most severely affecting bones, muscles and connective tissues. Current therapies include periodic intravenous infusion of supplementary recombinant enzyme (Enzyme Replacement Therapy–ERT) or bone marrow transplantation. However, ERT has limited efficacy due to poor penetration in some organs and tissues. Here, we investigated the potential of the β-D-xyloside derivative odiparcil as an oral GAG clearance therapy for Maroteaux–Lamy syndrome (Mucopolysaccharidosis type VI, MPS VI). In vitro, in bovine aortic endothelial cells, odiparcil stimulated the secretion of sulphated GAG into culture media, mainly of chondroitin sulphate (CS) /dermatan sulphate (DS) type. Efficacy of odiparcil in reducing intracellular GAG content was investigated in skin fibroblasts from MPS VI patients where odiparcil was shown to reduce efficiently the accumulation of intracellular CS with an EC₅₀ in the range of 1 μM. In vivo, in wild type rats, after oral administrations, odiparcil was well distributed, achieving μM concentrations in MPS VI disease-relevant tissues and organs (bone, cartilage, heart and cornea). In MPS VI Arylsulphatase B deficient mice (Arsb^-), after chronic oral administration, odiparcil consistently stimulated the urinary excretion of sulphated GAG throughout the treatment period and significantly reduced tissue GAG accumulation in liver and kidney. Furthermore, odiparcil diminished the pathological cartilage thickening observed in trachea and femoral growth plates of MPS VI mice. The therapeutic efficacy of odiparcil was similar in models of early (treatment starting in juvenile, 4 weeks old mice) or established disease (treatment starting in adult, 3 months old mice). Our data demonstrate that odiparcil effectively diverts the synthesis of cellular glycosaminoglycans into secreted soluble species and this effect can be used for reducing cellular and tissue GAG accumulation in MPS VI models. Therefore, our data reveal the potential of odiparcil as an oral GAG clearance therapy for MPS VI patients.

Lemon juice catalyzed C-C bond formation via C-H activation of methylarene: a sustainable synthesis of chromenopyrimidines

An economical and proficient approach has been developed for the synthesis of chromenopyrimidines via three-component reaction of thiobarbituric acid/barbituric acid, methylarenes and dimedone/1,3-cyclohexanedione by using lemon juice as a natural, biodegradable catalyst and TBHP as an oxidant. This transformation involves metal-free C-C bond formation via C-H activation of methylarenes under mild reaction conditions.

Nickel-catalyzed regioselective C–H acylation of chelating arenes: a new catalytic system for C–C bond formation via a radical process and its mechanistic explorations

An unprecedented acylation at the ortho C–H bond of chelating arenes via the Ni(ii)-catalyzed cross dehydrogenative coupling strategy has been developed here.

Palladium-catalyzed direct mono-aroylation of O-arylmethyl and aryl-substituted acetoxime ethers

An efficient palladium-catalyzed ortho-aroylation of O-arylmethyl and aryl-substituted acetoxime ethers has been developed; this method has high mono-site selectivity and does not require exogenous ligands. Under the direction of a simple exo-acetoxime auxiliary, a broad scope of masked arylmethyl alcohols and phenols as well as various aromatic aldehydes are compatible with this transformation, which probably follows a mechanistic pathway involving a six- or five-membered exo-cyclopalladated intermediate. The strategy can be expediently adopted to prepare synthetically valuable 1H-benzo[d][1,2]oxazines and benzo[d]isoxazoles. The directing group can be easily removed from the products to afford the functionalized diaryl ketones.

Palladium-catalyzed decarboxylative, decarbonylative and dehydrogenative C(sp2)-H acylation at room temperature

Over the past few decades, an impressive array of C-H activation methodology has been developed for organic synthesis. However, due to the inherent inertness of the C-H bonds (e.g. ∼110 kcal mol^-1 for the cleavage of C(aryl)-H bonds) harsh reaction conditions have been realized to overcome high energetic transition states resulting in a limited substrate scope and functional group tolerance. Therefore, the development of mild C-H functionalization protocols is in high demand to exploit the full potential of the C-H activation strategy in the synthesis of a complex molecular framework. Although, electron-rich substrates undergo electrophilic metalation under relatively mild conditions, electron-deficient substrates proceed through a rate-limiting C-H insertion under forcing conditions at high temperature. In addition, a stoichiometric amount of toxic silver salt is frequently used in palladium catalysis to facilitate the C-H activation process which is not acceptable from the environmental and industrial standpoint. We report herein, a Pd(ii)-catalyzed decarboxylative C-H acylation of 2-arylpyridines with α-ketocarboxylic acids under mild conditions. The present protocol does not require stoichiometric silver(i) salts as additives and proceeds smoothly at ambient temperature. A novel decarbonylative C-H acylation reaction has also been accomplished using aryl glyoxals as acyl surrogates. Finally, a practical C-H acylation via a dehydrogenative pathway has been demonstrated using commercially available benzaldehydes and aqueous hydroperoxides. We also disclose that acetonitrile solvent is optimal for the acylation reaction at room temperature and has a prominent role in the reaction outcome. Control experiments suggest that the acylation reaction via decarboxylative, decarbonylative and dehydrogenative proceeds through a radical pathway. Thus we disclose a practical protocol for the sp² C-H acylation reaction.

Synthetic Xylosides: Probing the Glycosaminoglycan Biosynthetic Machinery for Biomedical Applications

Glycosaminoglycans (GAGs) are polysaccharides ubiquitously found on cell surfaces and in the extracellular matrix (ECM). They regulate numerous cellular signaling events involved in many developmental and pathophysiological processes. GAGs are composed of complex sequences of repeating disaccharide units, each of which can carry many different modifications. The tremendous structural variations account for their ability to bind many proteins and thus, for their numerous functions. Although the sequence of GAG biosynthetic events and the enzymes involved mostly were deduced a decade ago, the emergence of tissue or cell specific GAGs from a nontemplate driven process remains an enigma. Current knowledge favors the hypothesis that macromolecular assemblies of GAG biosynthetic enzymes termed "GAGOSOMEs" coordinate polymerization and fine structural modifications in the Golgi apparatus. Distinct GAG structures arise from the differential channeling of substrates through the Golgi apparatus to various GAGOSOMEs. As GAGs perform multiple regulatory roles, it is of great interest to develop molecular strategies to selectively interfere with GAG biosynthesis for therapeutic applications. In this Account, we assess our present knowledge on GAG biosynthesis, the manipulation of GAG biosynthesis using synthetic xylosides, and the unrealized potential of these xylosides in various biomedical applications. Synthetic xylosides are small molecules consisting of a xylose attached to an aglycone group, and they compete with endogenous proteins for precursors and biosynthetic enzymes to assemble GAGs. This competition reduces endogenous proteoglycan-bound GAGs while increasing xyloside-bound free GAGs, mostly chondroitin sulfate (CS) and less heparan sulfate (HS), resulting in a variety of biological consequences. To date, hundreds of xylosides have been published and the importance of the aglycone group in determining the structure of the primed GAG chains is well established. However, the structure-activity relationship has long been cryptic. Nonetheless, xylosides have been designed to increase HS priming, modified to inhibit endogenous GAG production without priming, and engineered to be more biologically relevant. Synthetic xylosides hold great promise in many biomedical applications and as therapeutics. They are small, orally bioavailable, easily excreted, and utilize the host cell biosynthetic machinery to assemble GAGs that are likely nonimmunogenic. Various xylosides have been shown, in different biological systems, to have anticoagulant effects, selectively kill tumor cells, abrogate angiogenic and metastatic pathways, promote angiogenesis and neuronal growth, and affect embryonic development. However, most of these studies utilized the commercially available one or two β-D-xylosides and focused on the impact of endogenous proteoglycan-bound GAG inhibition on biological activity. Nevertheless, the manipulation of cell behavior as a result of stabilizing growth factor signaling with xyloside-primed GAGs is also reckonable but underexplored. Recent advances in the use of molecular modeling and docking simulations to understand the structure-activity relationships of xylosides have opened up the possibility of a more rational aglycone design to achieve a desirable biological outcome through selective priming and inhibitory activities. We envision these advances will encourage more researchers to explore these fascinating xylosides, harness the GAG biosynthetic machinery for a wider range of biomedical applications, and accelerate the successful transition of xyloside-based therapeutics from bench to bedside.

Drugs affecting glycosaminoglycan metabolism

Glycosaminoglycans (GAGs) are charged polysaccharides ubiquitously present at the cell surface and in the extracellular matrix. GAGs are crucial for cellular homeostasis, and their metabolism is altered during pathological processes. However, little consideration has been given to the regulation of the GAG milieu through pharmacological interventions. In this review, we provide a classification of small molecules affecting GAG metabolism based on their mechanism of action. Furthermore, we present evidence to show that clinically approved drugs affect GAG metabolism and that this could contribute to their therapeutic benefit.

Ag-catalyzed C-H/C-C bond functionalization

Silver, known and utilized since ancient times, is a coinage metal, which has been widely used for various organic transformations in the past few decades. Currently, the silver-catalyzed reaction is one of the frontier areas in organic chemistry, and the progress of research in this field is very rapid. Compared with other transition metals, silver has long been believed to have low catalytic efficiency, and most commonly, it is used as either a cocatalyst or a Lewis acid. Interestingly, the discovery of Ag-catalysis has been significantly improved in recent years. Especially, Ag(i) has been demonstrated as an important and versatile catalyst for a variety of organic transformations. However, so far, there has been no systematic review on Ag-catalyzed C-H/C-C bond functionalization. In this review, we will focus on the development of Ag-catalyzed C-H/C-C bond functionalization and the corresponding mechanism.

Palladium-catalyzed decarboxylative ortho-aroylation of N-acetyl-1,2,3,4-tetrahydroquinolines with α-oxoarylacetic acids

A mild and efficient palladium-catalyzed decarboxylative ortho-aroylation of N-acetyl-1,2,3,4-tetrahydroquinolines with α-oxoarylacetic acids via C–H bond activation is described. This protocol provides access to a series of C8-aroyl terahydroquinolines.

β-Xylopyranosides: synthesis and applications

In recent years, β-xylopyranosides have attracted interest due to the development of biomass-derived molecules. This review focuses on general routes for the preparation of β-xylopyranosides by chemical and enzymatic pathways and their main uses.

Silver catalyzed decarboxylative acylation of pyridine-N-oxides using α-oxocarboxylic acids

Silver catalyzed acylation of pyridine-N-oxides by α-oxocarboxylic acid is demonstrated. This decarboxylative acylation using a metal catalyst takes place at 50 °C via a radical process.

Pd-catalysed ortho-C-H Acylation/cross Coupling of 2-arylbenzo[d]thiazoles with Aldehydes Using tert-butyl Hydroperoxide as Oxidant

An efficient palladium-catalysed protocol for direct C–H bond acylation by cross coupling of 2-arylbenzo[d]thiazoles and aldehydes using tert-butyl hydroperoxide as the oxidant is reported. The process provides a useful method for the synthesis of aromatic ketones directly from aldehydes. In addition, the reaction can tolerate various functional groups in good yield with high regioselectivity.