Continuous Flow C-Glycosylation via Metal–Halogen Exchange: Process Understanding and Improvements toward Efficient Manufacturing of Remdesivir

Will the next generation of chemical plants be in miniaturized flow reactors?

For decades, a production paradigm based on centralized, stepwise, large scale processes has dominated the chemical industry horizon. While effective to meet an ever increasing demand for high value-added chemicals, the so-called macroscopic batch reactors are also associated with inherent weaknesses and threats; some of the most obvious ones were tragically illustrated over the past decades with major industrial disasters and impactful disruptions of advanced chemical supplies. The COVID pandemic has further emphasized that a change in paradigm was necessary to sustain chemical production with an increased safety, reliable supply chains and adaptable productivities. More than a decade of research and technology development has led to alternative and effective chemical processes relying on miniaturised flow reactors (a.k.a. micro and mesofluidic reactors). Such miniaturised reactors bear the potential to solve safety concerns and to improve the reliability of chemical supply chains. Will they initiate a new paradigm for a more localized, safe and reliable chemical production?

Design and characterization of a flow reaction calorimeter based on FlowPlate® Lab and Peltier elements

Microscale flow reaction calorimeter based on commercially available hastelloy C-22 microreactor for isoperibolic and isothermal operation mode.

Studies on the synthesis of 1'-CN-triazolyl-C-ribosides

The search for broad-spectrum antiviral compounds is a continuous mandatory effort. The recent approval of the first C-nucleoside carrying a nitrile as a substituent at the C1' position of the ribose ring has raised interest in this underexplored substitution pattern. We have previously reported the development of different 1,2,3-triazolyl-C-ribonucleosides with anticancer and antiviral activities. Herein we report our results on the incorporation of a C1'-CN group in 1,2,3-triazolyl-C-ribonucleosides.

Facile and Scalable Methodology for the Pyrrolo[2,1-f][1,2,4]triazine of Remdesivir

Pyrrolo[2,1-f][1,2,4]triazine (1) is an important regulatory starting material in the production of the antiviral drug remdesivir. Compound 1 was produced through a newly developed synthetic methodology utilizing simple building blocks such as pyrrole, chloramine, and formamidine acetate by examining the mechanistic pathway for the process optimization exercise. Triazine 1 was obtained in 55% overall yield in a two-vessel-operated process. This work describes the safety of the process, impurity profiles and control, and efforts toward the scale-up of triazine for the preparation of kilogram quantity.

Total synthesis of remdesivir

Remdesivir, the first drug approved by the FDA to treat COVID-19, is in high demand for patients infected with the SARS-CoV-2 virus. Herein, we report a facile approach minimizing the protecting group manipulations to afford remdesivir in good overall yield.

CRYSTAL STRUCTURE OF 3-tert-BUTYL- PYRAZOLO[5,1-с][1,2,4]TRIAZINE-3,4-DIYL DICARBOXYLATES

By single crystal X-ray diffraction the structures of (trans-)7-R¹-8-methyl-3-tert-butyl-3,4-dihydropyrazolo[5,1-с][1,2,4]triazine-3,4-diyl dibenzoates 3а, 4а (R¹ = H, Br) and diacetate 3b (R¹ = H) are studied for the first time. The compounds are synthesized by oxidative bromination of respective 1,4-dihydropyrazolo[5,1-c][1,2,4]triazines in the presence of carboxylic acids. Dicarboxylates adopt a twist-conformation with the equatorial (3a) or axial (3b, 4a) orientation of tert-butyl groups relative to the heterocycle. In the case of diacetate 3b, a decrease in the thermal motion of the O4–C16–C17 fragment along with a decrease in the unit cell volume are observed on cooling from 300 K to 200 K. Bond lengths, torsion angles, and molecular packings in the crystals are discussed.

Evolution of the Synthesis of Remdesivir. Classical Approaches and Most Recent Advances

The broad-spectrum antiviral Remdesivir, a monophosphate nucleoside analogue prodrug (ProTide), was repurposed. In May 2020, it received emergency approval by the FDA, being the first drug approved to fight the new coronavirus (COVID-19) disease which targets the virus directly. The main synthetic strategies toward Remdesivir, and their relevant modifications, are presented and discussed, to provide a panoramic view of the state-of-the-art and the more important advances in this field. Recent progress, proposed improvements, and uses of novel technologies for the synthetic sequence are also detailed.

Quest for a Cure: Potential Small-Molecule Treatments for COVID-19, Part 2

During the first year of the outbreak of the COVID-19 pandemic, many drugs and drug candidates have been evaluated as treatment options. None yet has proved to be an effective cure, but progress in controlling the disease has been made. In June 2020 we published an article that described the mechanistic rationale behind the repurposing of seven licensed drugs in clinical trials for the treatment of COVID-19 and reviewed synthetic routes to these drugs. Several developments have occurred since then. Remdesivir (trade name Veklury) has been approved for use in the U.S. and Europe. Dexamethasone, a steroid drug first approved in 1959, has shown mortality reduction in severe COVID patients. Molnupiravir, a new and promising oral antiviral drug, is being studied in late-stage clinical trials. In this review, we update synthetic work that has been recently published on remdesivir, provide an overview of several routes to molnupiravir, and review classical routes to dexamethasone as well as some of those more recently developed.

Synthesis and crystal structures of 7,8-bromo (dibromo)-3-tert-butylpyrazolo[5,1-c][1,2,4]triazines

Single crystal structures in a series of 7-bromo-, 8-bromo-, and 7,8-dibromo-3-tert-butylpyrazolo[5,1-c][1,2,4]triazin-4(1H)-ones have been investigated by X-ray diffraction. Novel 7-bromo- and 7,8-dibromo-3-tert-butylpyrazolo[5,1-c][1,2,4]triazines were synthesized by reduction of triazine carbonyl with dehydrative aromatization in acidic media, and their XRD structural features were compared with that of the 4-oxo analogs. The lengths and bond angles and the packing of molecules in crystals have been considered. Non-valence interactions for some of the studied compounds were observed. Correlations between the presence of bromine atoms at different positions and structural features are determined.

GRAPHICAL ABSTRACT

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11224-021-01768-0.

Weinreb Amide Approach to the Practical Synthesis of a Key Remdesivir Intermediate

Currently, remdesivir is the first and only FDA-approved antiviral drug for COVID-19 treatment. Adequate supplies of remdesivir are highly warranted to cope with this global public health crisis. Herein, we report a Weinreb amide approach for preparing the key intermediate of remdesivir in the glycosylation step where overaddition side reactions are eliminated. Starting from 2,3,5-tri-O-benzyl-d-ribonolactone, the preferred route consisting of three sequential steps (Weinreb amidation, O-TMS protection, and Grignard addition) enables a high-yield (65%) synthesis of this intermediate at a kilogram scale. In particular, the undesirable PhMgCl used in previous methods was successfully replaced by MeMgBr. This approach proved to be suitable for the scalable production of the key remdesivir intermediate.

COVID-19 into Chemical Science Perspective: Chemical Preventive Measures and Drug Development

COVID-19 facts and literature are discussed into chemical science intuition highlighting the direct role of chemistry to the ongoing global pandemic by covering structural identification of the virus, chemical preventive measures and development of drugs. We reviewed the four most promising repurposed drugs which are presently being investigated in mass clinical trials on COVID-19 infected persons and synthetic routes of these drugs with their recent advancement. Chemical preventive measures such as soap water, hand sanitizer and disinfectant are the only available options in the arsenal to fight against COVID-19, till an effective medicine or vaccine will be made available. As such the present review will focus on the mode of action of the major chemical preventives.