Programmable One-Pot Synthesis of Heparin Pentasaccharide Fondaparinux

Precision Synthesis and Antiliver Fibrosis Activity of a Highly Branched Acidic 63-Mer Pectin Polysaccharide

Natural polysaccharides possess various biological functions and have become increasingly important as drug candidates for biomedical development. However, the accessibility to multiple-branched and large-sized acidic polysaccharides with well-defined structures and the identification of related active glycan domains remain challenging. Here, we report the precision synthesis of a highly branched acidic pectin polysaccharide up to a 63-mer containing 10 different glycosidic linkages from Lycium barbarum. The synthetic strategy relies on highly stereoselective modular assembly of an orthogonally protected decasaccharide backbone, efficient synthesis of three side chain glycans by the integration of stereocontrolled one-pot chemoselective glycosylations and a hydrogen-bond-mediated aglycone delivery approach, and convergent assembly of the target polysaccharide in a branched site-specific glycosylation manner via flexible orthogonal protecting group manipulations. Structure-activity relationship studies of synthetic polysaccharide 63-mer and its short fragments (9-mer, 10-mer, 11-mer, and 33-mer) suggest that the decasaccharide as an active glycan domain exhibits better antiliver fibrosis activity.

Bioengineered heparin: Advances in production technology

Heparin, a highly sulfated glycosaminoglycan, is considered an indispensable anticoagulant with diverse therapeutic applications and has been a mainstay in medical practice for nearly a century. Its potential extends beyond anticoagulation, showing promise in treating inflammation, cancer, and infectious diseases such as COVID-19. However, its current sourcing from animal tissues poses challenges due to variable structures and adulterations, impacting treatment efficacy and safety. Recent advancements in metabolic engineering and synthetic biology offer alternatives through bioengineered heparin production, albeit with challenges such as controlling molecular weight and sulfonation patterns. This review offers comprehensive insight into recent advancements, encompassing: (i) the metabolic engineering strategies in prokaryotic systems for heparin production; (ii) strides made in the development of bioengineered heparin; and (iii) groundbreaking approaches driving production enhancements in eukaryotic systems. Additionally, it explores the potential of recombinant Chinese hamster ovary cells in heparin synthesis, discussing recent progress, challenges, and future prospects, thereby opening up new avenues in biomedical research.

Multifaceted Heparin: Diverse Applications beyond Anticoagulant Therapy

Heparin, a naturally occurring polysaccharide, has fascinated researchers and clinicians for nearly a century due to its versatile biological properties and has been used for various therapeutic purposes. Discovered in the early 20th century, heparin has been a key therapeutic anticoagulant ever since, and its use is now implemented as a life-saving pharmacological intervention in the management of thrombotic disorders and beyond. In addition to its known anticoagulant properties, heparin has been found to exhibit anti-inflammatory, antiviral, and anti-tumorigenic activities, which may lead to its widespread use in the future as an essential drug against infectious diseases such as COVID-19 and in various medical treatments. Furthermore, recent advancements in nanotechnology, including nano-drug delivery systems and nanomaterials, have significantly enhanced the intrinsic biofunctionalities of heparin. These breakthroughs have paved the way for innovative applications in medicine and therapy, expanding the potential of heparin research. Therefore, this review aims to provide a creation profile of heparin, space for its utilities in therapeutic complications, and future characteristics such as bioengineering and nanotechnology. It also discusses the challenges and opportunities in realizing the full potential of heparin to improve patient outcomes and elevate therapeutic interventions.

Enzyme-mediated green synthesis of glycosaminoglycans and catalytic process intensification

Glycosaminoglycans (GAGs) are a family of structurally complex heteropolysaccharides that play pivotal roles in biological functions, including the regulation of cell proliferation, enzyme inhibition, and activation of growth factor receptors. Therefore, the synthesis of GAGs is a hot research topic in drug development. The enzymatic synthesis of GAGs has received widespread attention due to their eco-friendly nature, high regioselectivity, and stereoselectivity. The enhancement of the enzymatic synthesis process is the key to its industrial applications. In this review, we overviewed the construction of more efficient in vitro biomimetic synthesis systems of glycosaminoglycans and presented the different strategies to improve enzyme catalysis, including the combination of chemical and enzymatic methods, solid-phase synthesis, and protein engineering to solve the problems of enzyme stability, separation and purification of the product, preparation of structurally defined sugar chains, etc., and discussed the challenges and opportunities in large-scale green synthesis of GAGs.

Quality control, safety assessment and preparation approaches of low molecular weight heparin

Low Molecular Weight Heparins (LMWHs) are well-established for use in the prevention and treatment of thrombotic diseases, and as a substitute for unfractionated heparin (UFH) due to their predictable pharmacokinetics and subcutaneous bioavailability. LMWHs are produced by various depolymerization methods from UFH, resulting in heterogeneous compounds with similar biochemical and pharmacological properties. However, the delicate supply chain of UFH and potential contamination from animal sources require new manufacturing approaches for LMWHs. Various LMWH preparation methods are emerging, such as chemical synthesis, enzymatic or chemical depolymerization and chemoenzymatic synthesis. To establish the sameness of active ingredients in both innovator and generic LMWH products, the Food and Drug Administration has implemented a stringent scientific method of equivalence based on physicochemical properties, heparin source material and depolymerization techniques, disaccharide composition and oligosaccharide mapping, biological and biochemical properties, and in vivo pharmacodynamic profiles. In this review, we discuss currently available LMWHs, potential manufacturing methods, and recent progress for manufacturing quality control of these LMWHs.

Overview of the current procedures in synthesis of heparin saccharides

Natural heparin, a glycosaminoglycan consisting of repeating hexuronic acid and glucosamine linked by 1 → 4 glycosidic bonds, is the most widely used anticoagulant. To subvert the dependence on animal sourced heparin, alternative methods to produce heparin saccharides, i.e., either heterogenous sugar chains similar to natural heparin, or structurally defined oligosaccharides, are becoming hot subjects. Although the success by chemical synthesis of the pentasaccharide, fondaparinux, encourages to proceed through a chemical approach generating homogenous product, synthesizing larger oligos is still cumbersome and beyond reach so far. Alternatively, the chemoenzymatic pathway exhibited exquisite stereoselectivity of glycosylation and regioselectivity of modification, with the advantage to skip the tedious protection steps unavoidable in chemical synthesis. However, to a scale of drug production needed today is still not in sight. In comparison, a procedure of de novo biosynthesis in an organism could be an ultimate goal. The main purpose of this review is to summarize the current available/developing strategies and techniques, which is expected to provide a comprehensive picture for production of heparin saccharides to replenish or eventually to replace the animal derived products. In chemical and chemoenzymatic approaches, the methodologies are discussed according to the synthesis procedures: building block preparation, chain elongation, and backbone modification.

Glycosaminoglycan microarrays for studying glycosaminoglycan-protein systems

More than 3000 proteins are now known to bind to glycosaminoglycans (GAGs). Yet, GAG-protein systems are rather poorly understood in terms of selectivity of recognition, molecular mechanism of action, and translational promise. High-throughput screening (HTS) technologies are critically needed for studying GAG biology and developing GAG-based therapeutics. Microarrays, developed within the past two decades, have now improved to the point of being the preferred tool in the HTS of biomolecules. GAG microarrays, in which GAG sequences are immobilized on slides, while similar to other microarrays, have their own sets of challenges and considerations. GAG microarrays are rapidly becoming the first choice in studying GAG-protein systems. Here, we review different modalities and applications of GAG microarrays presented to date. We discuss advantages and disadvantages of this technology, explain covalent and non-covalent immobilization strategies using different chemically reactive groups, and present various assay formats for qualitative and quantitative interpretations, including selectivity screening, binding affinity studies, competitive binding studies etc. We also highlight recent advances in implementing this technology, cataloging of data, and project its future promise. Overall, the technology of GAG microarray exhibits enormous potential of evolving into more than a mere screening tool for studying GAG - protein systems.

Microwave-assisted synthesis of highly sulfated mannuronate glycans as potential inhibitors against SARS-CoV-2

Algae-based marine carbohydrate drugs are typically decorated with negative ion groups such as carboxylate and sulfate groups. However, the precise synthesis of highly sulfated alginates is challenging, thus impeding their structure-activity relationship studies. Herein we achieve a microwave-assisted synthesis of a range of highly sulfated mannuronate glycans with up to 17 sulfation sites by overcoming the incomplete sulfation due to the electrostatic repulsion of crowded polyanionic groups. Although the partially sulfated tetrasaccharide had the highest affinity for the receptor binding domain (RBD) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant, the fully sulfated octasaccharide showed the most potent interference with the binding of the RBD to angiotensin-converting enzyme 2 (ACE2) and Vero E6 cells, indicating that the sulfated oligosaccharides might inhibit the RBD binding to ACE2 in a length-dependent manner.

Structural and Functional Analysis of Heparosan Synthase 2 from Pasteurella multocida (PmHS2) to Improve the Synthesis of Heparin

Heparin is a widely used drug to treat thrombotic disorders in hospitals. Heparosan synthase 2 from Pasteurella multocida (PmHS2) is a key enzyme used for the chemoenzymatic synthesis of heparin oligosaccharides. It has both activities: glucosaminyl transferase activity and glucuronyl transferase activity; however, the mechanism to carry out the glyco-oligomerization is unknown. Here, we report crystal structures of PmHS2 constructs with bound uridine diphosphate (UDP) and a cryo-EM structure of PmHS2 in complex with UDP and a heptasaccharide (NS 7-mer) substrate. Using a LC-MC analytical method, we discovered the enzyme displays both a two-step concerted oligomerization mode and a distributive oligomerization mode depending on the non-reducing end of the starting oligosaccharide primer. Removal of 7 amino acid residues from the C-terminus results in an enzymatically active monomer instead of dimer and loses the concerted oligomerization mode of activity. In addition, the monomer construct can transfer N-acetyl glucosamine at a substrate concentration that is ∼7-fold higher than wildtype enzyme. It was also determined that an F529A mutant can transfer an N-sulfo glucosamine (GlcNS) saccharide from a previously inactive UDP-GlcNS donor. Performing the glyco-transfer reaction at a high substrate concentration and the capability of using unnatural donors are desirable to simplify the chemoenzymatic synthesis to prepare heparin-based therapeutics.

Thiourea-Cu(OTf)2/NIS-synergistically promoted stereoselective glycoside formation with 2-azidoselenoglycosides or thioglycosides as donors

A novel promoter system for glycosylation is described. A catalytic amount of thiourea and Cu(OTf)2 together with a slight excess of N-iodosuccinimide synergistically promotes glycosylation at room temperature. The combination of reagents applies to some 2-azidoselenoglycoside and thioglycoside donors. A wide range of alcoholic acceptors underwent smooth conversion to O-(2-azido)glycosides with good stereoselectivities. In addition, the value of this method has been highlighted by its convenient operation and outstanding functional group compatibility.

A review on multifaceted biomedical applications of heparin nanocomposites: Progress and prospects

Advances in polymer-based nanocomposites have revolutionized biomedical applications over the last two decades. Heparin (HP), being a highly bioactive polymer of biological origin, provides strong biotic competence to the nanocomposites, broadening the horizon of their applicability. The efficiency, biocompatibility, and biodegradability properties of nanomaterials significantly improve upon the incorporation of heparin. Further, inclusion of structural/chemical derivatives, fractionates, and mimetics of heparin enable fabrication of versatile nanocomposites. Modern nanotechnological interventions have exploited the inherent biofunctionalities of heparin by formulating various nanomaterials, including inorganic/polymeric nanoparticles, nanofibers, quantum dots, micelles, liposomes, and nanogels ensuing novel functionalities targeting diverse clinical applications involving drug delivery, wound healing, tissue engineering, biocompatible coatings, nanosensors and so on. On this note, the present review explicitly summarises the recent HP-oriented nanotechnological developments, with a special emphasis on the reported successful engagement of HP and its derivatives/mimetics in nanocomposites for extensive applications in the laboratory and health-care facility. Further, the advantages and limitations/challenges specifically associated with HP in nanocomposites, undertaken in this current review are quintessential for future innovations/discoveries pertaining to HP-based nanocomposites.

Synthesis of Anticoagulant Pentasaccharide Fondaparinux via 3,5-Dimethyl-4-(2'-phenylethynylphenyl)phenyl Glycosides

Here, we disclosed a convenient procedure for the preparation of EPP [3,5-dimethyl-4-(2'-phenylethynylphenyl)phenyl] glycosides and their application to an effective synthesis of fondaparinux, the clinically approved anticoagulant heparin pentasaccharide. The use of EPP glycosides in the one-pot orthogonal glycosylation for the synthesis of heparin-like tetrasaccharides has also been achieved.

Designing Smaller, Synthetic, Functional Mimetics of Sulfated Glycosaminoglycans as Allosteric Modulators of Coagulation Factors

Natural glycosaminoglycans (GAGs) are arguably the most diverse collection of natural products. Unfortunately, this bounty of structures remains untapped. Decades of research has realized only one GAG-like synthetic, small-molecule drug, fondaparinux. This represents an abysmal output because GAGs present a frontier that few medicinal chemists, and even fewer pharmaceutical companies, dare to undertake. GAGs are heterogeneous, polymeric, polydisperse, highly water soluble, synthetically challenging, too rapidly cleared, and difficult to analyze. Additionally, GAG binding to proteins is not very selective and GAG-binding sites are shallow. This Perspective attempts to transform this negative view into a much more promising one by highlighting recent advances in GAG mimetics. The Perspective focuses on the principles used in the design/discovery of drug-like, synthetic, sulfated small molecules as allosteric modulators of coagulation factors, such as antithrombin, thrombin, and factor XIa. These principles will also aid the design/discovery of sulfated agents against cancer, inflammation, and microbial infection.

Pharmacology of Heparin and Related Drugs: An Update

Heparin has been used extensively as an antithrombotic and anticoagulant for close to 100 years. This anticoagulant activity is attributed mainly to the pentasaccharide sequence, which potentiates the inhibitory action of antithrombin, a major inhibitor of the coagulation cascade. More recently it has been elucidated that heparin exhibits anti-inflammatory effect via interference of the formation of neutrophil extracellular traps and this may also contribute to heparin's antithrombotic activity. This illustrates that heparin interacts with a broad range of biomolecules, exerting both anticoagulant and nonanticoagulant actions. Since our previous review, there has been an increased interest in these nonanticoagulant effects of heparin, with the beneficial role in patients infected with SARS2-coronavirus a highly topical example. This article provides an update on our previous review with more recent developments and observations made for these novel uses of heparin and an overview of the development status of heparin-based drugs. SIGNIFICANCE STATEMENT: This state-of-the-art review covers recent developments in the use of heparin and heparin-like materials as anticoagulant, now including immunothrombosis observations, and as nonanticoagulant including a role in the treatment of SARS-coronavirus and inflammatory conditions.

Design and Synthesis of Neutralizable Fondaparinux

Fondaparinux, a clinically approved anticoagulant pentasaccharide for the treatment of thrombotic diseases, displays better efficacy and biosafety than other heparin-based anticoagulant drugs. However, there is no suitable antidote available for fondaparinux to efficiently manage its potential bleeding risks, thereby precluding its widespread use. Herein, we describe a convergent and stereocontrolled approach to efficiently synthesize an aminopentyl-functionalized pentasaccharide, which is further used to prepare fondaparinux-based biotin conjugates and clusters. Biological activity evaluation demonstrates that the anticoagulant activity of the fondaparinux-based biotin conjugate and trimer is, respectively, neutralized by avidin and protamine as effective antidotes. This work suggests that our synthetic biotin conjugate and trimer have potential for the development of neutralizable and safe anticoagulant drugs.

Facile chemoenzymatic synthesis of unmodified anticoagulant ultra-low molecular weight heparin

A chemoenzymatic approach, mimicking the biosynthetic pathway of heparin and heparan sulfate (HS), has been well developed to prepare a series of structurally well-defined heparin oligosaccharides with excellent anticoagulant activity in good overall yields.

Developments in the Chemical Synthesis of Heparin and Heparan Sulfate

Heparin and heparan sulfate represent key members of the glycosaminoglycan family of carbohydrates and underpin considerable repertoires of biological importance. As such, their efficiency of synthesis represents a key requirement, to further understand and exploit the H/HS structure-to-biological function axis. In this review we focus on chemical approaches to and methodology improvements for the synthesis of these essential sugars (from 2015 onwards). We first consider advances in accessing the heparin-derived pentasaccharide anticoagulant fondaparinux. This is followed by heparan sulfate targets, including key building block synthesis, oligosaccharide construction and chemical sulfation techniques. We end with a consideration of technological improvements to traditional, solution-phase synthesis approaches that are increasingly being utilised.

Sequential activation of thioglycosides enables one-pot glycosylation

This review describes recent developments in relative reactivity value (RRV) controlled sequential glycosylation, pre-activation based iterative glycosylation, and sulfoxide activation initiated one-pot glycosylation.

Synthetic Carbohydrate Chemistry and Translational Medicine

The importance of post-translational glycosylation in protein structure and function has gained significant clinical relevance recently. The latest developments in glycobiology, glycochemistry, and glycoproteomics have made the field more manageable and relevant to disease progression and immune-response signaling. Here, we summarize the current progress in glycoscience, including the new methodologies that have led to the introduction of programmable and automatic as well as large-scale enzymatic synthesis, and the development of glycan array, glycosylation probes, and inhibitors of carbohydrate-associated enzymes or receptors. These novel methodologies and tools have facilitated our understanding of the significance of glycosylation and development of carbohydrate-derived medicines that bring the field to the next level of scientific and medical significance.

Chemoselective activation of ethyl vs. phenyl thioglycosides: one-pot synthesis of oligosaccharides

Ethyl and phenyl thioglycosides are the two most common types of thioglycoside donors in carbohydrate chemistry. However, the chemoselective activation of ethyl vs. phenyl thioglycosides is very rare in the literature. In this work, ethyl thioglycosides could be readily activated with an N-trifluoromethylthiosaccharin/TMSOTf system in the presence of phenyl thioglycosides carrying the same or even more armed protecting group pattern. Both armed and disarmed thioglycosides exhibited high chemoselectivity towards the promoter system. Chemoselective glycosylation was subsequently applied to one-pot synthesis, thus providing an efficient means to oligosaccharides.

Advances in the preparation and synthesis of heparin and related products

Heparin is a naturally occurring glycosaminoglycan from livestock, principally porcine intestine, and is clinically used as an anticoagulant drug. A limitation to heparin production is that it depends on a single animal species and potential problems have been associated with animal-derived heparin. The contamination crisis in 2008 led to a search for new animal sources and the investigation of non-animal sources of heparin. Over the past 5 years, new animal sources, chemical, and chemoenzymatic methods have been introduced to prepare heparin-based drugs. In this review, we describe advances in the preparation and synthesis of heparin and related products.