Programmable One-Pot Synthesis of Heparin Pentasaccharide Fondaparinux.
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ABSTRACT:
SUBMITTER: Dey S
PROVIDER: S-EPMC7347301 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Heparin (H) and heparan sulfate (HS) belong to the glycosaminoglycan (GAG) family of oligosaccharides, and their sequences and sulfation patterns are known to regulate the functions of various proteins in biological processes. Among these, the 6-O-sulfation of HS/H contributes most significantly to the structural diversity and binding interactions. However, the synthesis of HS with defined sulfation patterns remains a major challenge. Herein, we report a highly efficient and programmable one-pot method for the synthesis of protected heparin pentasaccharides using thioglycoside building blocks with optimized relative reactivities to allow the selective deprotection and preparation of regiodefined sulfate derivatives.
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Project description:The programmable one-pot oligosaccharide synthesis method was designed to enable the rapid synthesis of a large number of oligosaccharides, using the software Optimer to search Building BLocks (BBLs) with defined relative reactivity values (RRVs) to be used sequentially in the one-pot reaction. However, there were only about 50 BBLs with measured RRVs in the original library and the method could only synthesize small oligosaccharides due to the RRV ordering requirement. Here, we increase the library to include 154 validated BBLs and more than 50,000 virtual BBLs with predicted RRVs by machine learning. We also develop the software Auto-CHO to accommodate more data handling and support hierarchical one-pot synthesis using fragments as BBLs generated by the one-pot synthesis. This advanced programmable one-pot method provides potential synthetic solutions for complex glycans with four successful examples demonstrated in this work.
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Project description:A highly efficient one-pot methodology is described for the synthesis of heparin and heparan sulfate oligosaccharides utilizing thioglycosides with well-defined reactivity as building blocks. L-Idopyranosyl and D-glucopyranosyl thioglycosides 5 and 10 were used as donors due to low reactivity of uronic acids as the glycosyl donors in the one-pot synthesis. The formation of uronic acids by a selective oxidation at C-6 was performed after assembly of the oligosaccharides. The efficiency of this programmable strategy with the flexibility for sulfate incorporation was demonstrated in the representative synthesis of disaccharides 17, 18, tetrasaccharide 23, and pentasaccharide 26.
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Project description:Heparin (HP) and heparan sulfate (HS) play important roles in many biological events. Increasing evidence has shown that the biological functions of HP and HS can be critically dependent upon their precise structures, including the position of the iduronic acids and sulfation patterns. However, unraveling the HP code has been extremely challenging due to the enormous structural variations. To overcome this hurdle, we investigated the possibility of assembling a library of HP/HS oligosaccharides using a preactivation-based, one-pot glycosylation method. A major challenge in HP/HS oligosaccharide synthesis is stereoselectivity in the formation of the cis-1,4-linkages between glucosamine and the uronic acid. Through screening, suitable protective groups were identified on the matching glycosyl donor and acceptor, leading to stereospecific formation of both the cis-1,4- and trans-1,4-linkages present in HP. The protective group chemistry designed was also very flexible. From two advanced thioglycosyl disaccharide intermediates, all of the required disaccharide modules for library preparation could be generated in a divergent manner, which greatly simplified building-block preparation. Furthermore, the reactivity-independent nature of the preactivation-based, one-pot approach enabled us to mix the building blocks. This allowed rapid assembly of twelve HP/HS hexasaccharides with systematically varied and precisely controlled backbone structures in a combinatorial fashion. The speed and the high yields achieved in glycoassembly without the need to use a large excess of building blocks highlighted the advantages of our approach, which can be of general use to facilitate the study of HP/HS biology. As a proof of principle, this panel of hexasaccharides was used to probe the effect of backbone sequence on binding with the fibroblast growth factor-2 (FGF-2). A trisaccharide sequence of 2-O-sulfated iduronic acid flanked by N-sulfated glucosamines was identified to be the minimum binding motif and N-sulfation was found to be critical. This provides useful information for further development of more potent compounds towards FGF-2 binding, which can have potential applications in wound healing and anticancer therapy.
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Project description:The one-pot synthesis of a target molecule in the same reaction vessel is widely considered to be an efficient approach in synthetic organic chemistry. In this review, the characteristics and limitations of various one-pot syntheses of biologically active molecules are explained, primarily involving organocatalytic methods as key tactics. Besides catalysis, the pot-economy concepts presented herein are also applicable to organometallic and organic reaction methods in general.
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Project description:A new method for oligosaccharide assembly that combines the advantages of one-pot synthesis and fluorous separation is described. After one-pot glycosylations are completed, a fluorous tag is introduced into the reaction mixture to selectively "catch" the desired oligosaccharide, which is rapidly separated from non-fluorous impurities by fluorous solid-phase extraction (F-SPE). Subsequent "release" of the fluo rous tag and F-SPE achieved the purification of the desired oligosaccharide without the use of time- and solvent-consuming silica gel chromatography. Linear and branched oligosaccharides have been synthesized with this approach in just a few hours (for the overall oligosaccharide assembly and purification process).
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Project description:Polypropionates-motifs with alternating methyl and hydroxy groups-are important segments of many natural products possessing high bioactivity and therapeutic value. Synthetic access to these structures remains an area of intensive interest, focusing on the establishment of the contiguous stereocentres and a desire for operational simplicity. Here we report an efficient strategy for the stereoselective assembly of polypropionates with three or four stereocentres through a three-step relay process that include Diels-Alder reaction, silylenol ether hydrolysis and Baeyer-Villiger oxidation. The stereochemistry and functionality of the resulting polypropionates depend on the substitution pattern of the diene and dienophile substrates of the Diels-Alder cycloaddition. More importantly, the relay sequence is effectively performed in one pot, and the product could potentially undergo the same sequence for further elaboration. Finally, the C1-C9 segment of the macrolide etnangien is constructed with four of the six stereogenic centres established using the relay sequence.Polypropionates are present in many natural products possessing high bioactivity and therapeutic value. Here the authors show a strategy for the stereoselective assembly of polypropionates with three or four stereocentres through a process that includes a Diels-Alder reaction, silylenol ether hydrolysis and Baeyer-Villiger oxidation.
| S-EPMC5612996 | biostudies-literature
Project description:BackgroundSepsis triggers dysfunction of coagulation and fibrinolytic systems leading to disseminated intravascular coagulation (DIC) that contributes to organ failure and death. Fondaparinux (FPX) is a synthetic pentasaccharide that binds to antithrombin (AT) and selectively inhibits factor (F) Xa and other upstream coagulation proteases but not thrombin (T).ObjectivesWe used a baboon model of lethal Escherichia coli sepsis to investigate the effects of FPX treatment on DIC, organ function, and outcome.MethodsTwo experimental groups were studied: (a) E. coli challenge (n = 4); and (b) E coli plus FPX (n = 4). Bacteremia was modeled by intravenous infusion of pathogen (1-2 × 1010 CFU/kg). Fondaparinux (0.08 mg/kg) was administered subcutaneously, 3 h prior to and 8 h after bacteria infusion.ResultsBacteremia rapidly increased plasma levels of inhibitory complexes of AT with coagulation proteases. Activation markers of both intrinsic (FXIa-AT), and extrinsic (FVIIa-AT) pathways were significantly reduced in FPX-treated animals. Factor Xa-AT and TAT complexes were maximal at 4 to 8 h post challenge and reduced >50% in FPX-treated animals. Fibrinogen consumption, fibrin generation and degradation, neutrophil and complement activation, and cytokine production were strongly induced by sepsis. All parameters were significantly reduced, while platelet count was unchanged by the treatment. Fondaparinux infusion attenuated organ dysfunction, prolonged survival, and saved two of four challenged animals (log-rank Mantel-Cox test, P = .0067).ConclusionOur data indicate that FPX-mediated inhibition of coagulation prevents sepsis coagulopathy; protects against excessive complement activation, inflammation, and organ dysfunction; and provides survival benefit in E. coli sepsis.
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