| Author: | Chen, Qishu |
| Title: | Green synthesis of medicine and development of inhibitors for druggable proteins of SARS-COV-2 |
| Advisors: | Yu, Wing-yiu Michael (ABCT) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | COVID-19 (Disease) -- Treatment Viral proteins Drugs -- Environmental aspects Green chemistry Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Applied Biology and Chemical Technology |
| Pages: | xvii, 302 pages : color illustrations |
| Language: | English |
| Abstract: | As human activity continuously develops, especially after the impact of SARS-CoV-2, medicine-related manufacturing and development of new druggable targets for obscure diseases have become a noteworthy segment of the society. Green synthetic methods, especially step and atom economical methodologies towards sustainable and environmentally friendly medicine synthesis have long been the focus of scientists. Among the mainstream topics, one of them is methodology towards selective C–N bond formation. Nitrogen containing molecules serve as a fundamental part of peptide backbone, and amino groups serve as pervasive constructing element of pharmaceutical agents or synthetic intermediates. Thus, introducing amine structure motif into organic molecules with accurate selectivity plays an important role in modern chemistry, especially in medicine synthesis. While classical C(sp3)–H activation provided us many choices in regioselectivity, most of the developed reactions target at activated C–H bonds, possibly due to the reason that unactivated C–H bond own similar C–H activation energy. Also, there are still reactivity beyond the reach of classical C–H activation. Alkenes, as abundant organic resources in reserve, have been standing under the spotlight for its functionalization recently. The concept “metal-walk”, which represents the migration of metal through reversible β-hydride elimination / migratory insertion, provides another pathway towards unactivated C(sp3)–N formation. In Chapter 2, we report a selective C(sp3)–H amidation of alkenes directed by thioether group, with dioxazolones as the amide source, and Ni–H as the catalyst. Due to the preference for five-membered nickelacycle, the Ni–H migration would be terminated at γ-site, selectively and remote from the alkene group. The reaction can be achieved at ideal yields (up to 90% yield) and remarkable selectivity (γ-product : other isomers up to 24:1), with a wide substrate scope (>40 examples reported). As SARS-CoV-2 emerged in human population in 2019, COVID-19 and its therapeutic treatment quickly dominated human debate in recent years. The disease rapidly spread around the world, with quick generation of new variants. Despite the grievous harm it caused, medication towards SARS-CoV-2 remained largely unexplored. SARS-CoV-2 encodes 16 non-structural proteins (nsps) in total, which serve as the key enzymes in the replication of the virus. Among the enzymes encoded, nsp12, which is RNA dependent RNA polymerase (RdRp) for SARS-CoV-2, attracted the attention of scientists. RdRp is highly conservative, among all the variants and even among other members of coronavirus family. Even “drug repurposing” strategy brought us with several candidate, the proposed RdRp inhibitors still hold some disadvantages such as possibility of mutations, or poor pharmacokinetic (PK) properties, etc. We thus hope to seek for more ideal inhibitors of nsp12 towards more effective oral anti-SARS-CoV-2 candidates. In Chapter 3, we report a series of GS-441524 ester prodrug derivatives as COVID-19 oral drug candidate. We tested their inhibition reactivities towards SARS-CoV-2 RdRp, and their pharmacokinetic properties were also briefly examined. Compound 3-1, the cyclohexyl carboxylic ester prodrug examined, displayed the best inhibition ability, pharmacokinetic property, and oral bioavailability. The EC50 value of 3-1 is 0.26 μM, lower than that of GS-441524 (EC50 = 1.644 μM). F value of 3-1 also reached 53.4±3.4%, displaying an ideal oral bioavailability. Cmax of 3-1 through oral intake was close to that through intravenous injection, demonstrating the potential of 3-1 as oral medicine against COVID-19. We further renamed the compound as SHEN 26, and we went on to optimize its synthetic route and analyzed the quality y of industrial produced batch. We achieved a protection-esterification-deprotection 3-step route towards SHEN 26, without protecting the free amine group. We also determined and synthesized potential impurities and analyzed the purity of SHEN 26 from industrial kilogram batch. The purity of SHEN 26 reached 98.8%, with nearly all impurities meeting the acceptance criteria, demonstrating the feasibility of this route in industrial production of SHEN 26. Apart from RdRp, nsp14 is also a recently heated area. In the replication of SARS-CoV-2, nsp14 is responsible for the methylation (capping) progress of the single-strand RNA. The methylated RNA cap serves as a pivotal instrument, assisting the single-strand RNA with immune escape and further translation. S-Adenosyl methionine (SAM) serves as methyl source, which would give out a methyl group and turns into S-Adenosylhomocysteine (SAH) during methylation of single-strand RNA molecule. Thus, SAH analogues are considered as potential inhibitors for methyl transferases. Despite its great potential, few examples of SAH analogues as SARS-CoV-2 nsp14 inhibitors were reported, and room for improvements still exists, especially for their selectivity and cellular intake. To further pursue a better inhibitor, meanwhile being highly selective towards SARS-CoV-2 nsp14, we designed and synthesized a series of different SAH analogues in Chapter 3. Their inhibition ability against the SARS-CoV-2 nsp14 was tested with three different testing assays, at fixed concentration and in a dose-response manner. Among all inhibitors synthesized, ester MTI-ZC-007 and amide MTI-ZC-014 displayed the best inhibition ability against SARS-CoV-2 nsp14 ( 100% inhibition of both compounds at 10 μM and 50 μM; IC50 = 1.57 μM and 1.70 μM respectively, IC50-LCMS = 2.26 μM and 1.65 μM respectively), and we were also glad to see cellular inhibition of both MTI-ZC-007 and MTI-ZC-014 against SARS-CoV-2 virus (EC50 = 21.84 μM and 14.88 μM respectively) A brief docking study was conducted, and structure-activity relationship (SAR) regarding to this series of structure was also briefly discussed. |
| Rights: | All rights reserved |
| Access: | open access |
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