Metal-free C–H methylation and acetylation of heteroarenes with PEG-400

Abstract:

The generation of a methyl carbon source from renewable and cheap sources is challenging. Herein, we describe a novel and an efficient route for methylation and acetylation of aza-heteroarenes using PEG-400 under O₂ and TsOH·H₂O for the first time by tuning the reaction conditions using a different set of starting materials. The key features of the current protocol are oxidative C–O and C–C bond scission under metal-free conditions with good functional group tolerance, and a broad substrate scope. The potential applicability of the designed methodology was demonstrated for the synthesis of central nervous system (CNS) depressant and anticonvulsant drug molecules by a one-pot strategy.

Graphical Abstract:

Application and Highlights:

Introduction of a methyl group may have a remarkable impact on the biological properties of original molecules. Here we used PEG-400 as the reaction medium. Surprisingly, we observed unusual C-H methylation of quinazolinone and acetylation of other electron-deficient heteroarenes via oxidative C–C and C–O bond cleavage. N-Heteroarenes are important structural moieties observed in pharmaceuticals, natural products, and ligand scaffolds. Quinazolinones are prevalent structural species, and they have immense applications commonly found in medicinal and pharmaceutical chemistry with pharmacological activities, including anti-tumour, anti-inflammatory, anticonvulsant, and antimicrobial activities. A brief literature survey showed that the presence of a methyl group at the C₂-position and a substituted aromatic ring at the C₃-position are essential functionalities required for CNS depression and anticonvulsant activities of compounds. Advancements using PEG-400 have been achieved because it is environmentally benign in nature; recyclable; is a phase-transfer catalyst; is stable at high temperature; is easily available, has a low cost; and is biodegradable. The PEG-400 used in this work is more eco-friendly than the previously reported methylating reagent. This is the first report to use PEG-400 as a carbon source. Moreover, we demonstrated the potential applicability of the designed protocol for the construction of CNS depressant and anticonvulsant drug compounds from 2-amino-N-arylylbenzamide via sequential Csp²-Csp³ activation in a one-pot manner.

Research Team Members:

Dr. Jeh-Jeng Wang and Vishal Suresh Kudale

Representative Department: Department of Medicinal and Applied Chemistry, Kaohsiung Medical University

Introduction of Research Team:

Dr. Jeh-Jeng Wang, Professor, Department of Medicinal and Applied Chemistry, Kaohsiung Medical University. Tel: +886-7-3121101(Ext: 2275), E-mail: jjwang@kmu.edu.tw

Vishal Suresh Kudale, Doctoral fellow, Department of Medicinal and Applied Chemistry, Kaohsiung Medical University. Tel: +886-7-3121101(Ext: 2275), E-mail: vishalkudale90@gmail.com

Contact Email: jjwang@kmu.edu.tw

Publication: Green Chem. 2020 May 13; 22: 3506-3511.

Full-Text Article: https://doi.org/10.1039/D0GC01183E

Synthesis of the carbon dots for fast fluorescently sensing deferasirox in plasma

Currently, "quick screening" has been the focus of all testing development. For example, the virus detection of COVID-19, it is hoped to quickly understand whether a patient is infected with the disease in a quick screening method. Therefore, the rapid, timely and accurate quick screening technology has been fast developed in the diagnostic science. Therefore, this research is to develop a technology that can quickly and accurately analyze deferasirox in plasma. "Deferasirox" is commonly known as an iron excretion agent. It is often used in some diseases that require blood transfusion to eliminate the problem of excessive iron ions in the body. However, too much deferasirox will cause excessive iron ions to be eliminated and cause liver and renal toxicity. Thus, immediate monitoring of the blood concentration of deferasirox is a very important step in clinical treatment. In this research, the blood concentration of deferasirox can be easily measured on the patient just by a fluorescent spectrometer. The result can be obtained quickly, and the patient can be provided with more information. Rapid diagnosis and immediate corresponding changes can provide a diagnostic platform for the current emphasis on precision medicine.

 This research is designed to use fluorescent nanoparticles, "carbon dots" (CDs) to quickly screen the blood concentration of deferasirox. CDs is a novel material in recent years, and its preparation process is more convenient than ordinary nanoparticle. Only simple substances or even coffee grounds can be used to produce fluorescent CDs. CDs are tiny carbon nanoparticles with a size range of 1-10 nanometers. They are mainly composed of carbon atoms. Therefore, they have good electrical conductivity, high chemical stability, low environmental pollution, and a wide range of light. CDs are easy to obtain and low in price, so the cost is cheaper than other kinds of nanometer materials. Due to the above characteristics, CDs have become more and more important and applicable in recent years.

Fig. 1. The color of the liquid after the synthesis of "carbon dots", and the strong fluorescence performance of the "carbon dots" under ultraviolet light.

This research uses simple chemical raw materials (urea and citric acid) to synthesize high-fluorescence CDs by hydrothermal method, and the CDs were then coated with dopamine. When the copper ions exist, fluorescence of CDs will be largely quenched.  However, in the presence of deferasirox, the quenched fluorescence can be specifically restored. The degree of fluorescence recovery is used for specific and rapid quantification of deferasirox in plasma samples. Finally, this method was also applied to patients who actually took deferasirox. The detected blood concentration of deferasirox by this method was consistent with the clinical testing results. That confirmed that this method can quickly and specifically detect deferasirox in vivo, which not only makes the detection faster and more convenient, and the rapid test results can also be used for follow-up treatment or drug evaluation. For precision medicine, it can provide a powerful test platform.

Graphical Abstract

Application and Highlights:

1. The surface-derivative CDs have high fluorescent quantum yield and can be used in various fields.

2. When this CDs is in the presence of copper ions, its fluorescence will be largely quenched. However, when deferasirox is present, its quenched fluorescence can be specifically restored.

3. By using the fluorescence recovery degree of CDs, the deferasirox in plasma can be specifically and fast quantified.

4. This method was also applied to patients who actually took deferasirox. The detected blood concentration of deferasirox by this method was consistent with the clinical testing results.

5. This method not only makes the detection faster and more convenient, but can also use the rapid detection results for follow-up treatment or medication evaluation. It can provide a powerful detection platform for precision medicine.

Research Team Members: Chun-Chi Wang, Po-Tsang Huang, Hwang- Shang Kou, Shou-Mei Wu

Representative Department: School of Pharmacy, College of Pharmacy, Kaohsiung Medical University

Introduction of Research Team: The team has been committed to capillary electrophoresis, pharmaceutical analysis, genetic analysis, special probe and primer design, nanoparticle synthesis and application, etc. for many years. They have developed a number of technologies for drug monitoring or genetic testing, and obtained a number of patents.

Contact Email: chunchi0716@kmu.edu.tw

Publication: Sensors & Actuators: B. Chemical, 2020, 311: 127916.

Full-Text Article: https://www.sciencedirect.com/science/article/pii/S0925400520302641

L5 LDL linked to vascular aging in patients with Systemic Lupus Erythematosus (SLE)

SLE patients often have atherosclerotic complications at a young age but normal low-density lipoprotein (LDL) levels. Thus, this study was aimed to explain the paradoxical findings of early vascular aging (EVA) and normolipidemia in patients with SLE. In KMU, we focused on a different approach: the electronegative LDL. Human plasma LDL can be separated into five subfractions. L5 LDL, in particular, has been shown to be atherogenic, independent of LDL cholesterol. From here, we investigated the mechanisms of vascular aging in SLE patients.

Figure 1. SLE patients show elevated levels of atherogenic lipoproteins, L5 LDL.

The mass spectrometric analysis revealed that lysophosphatidylcholine (LPC) and platelet-activating factor (PAF) were increased in SLE-LDL and L5.

LPC and PAF are bioactive lipids, showing the capability to induce inflammatory changes in vascular cells both in vivo and in vitro. In this study, repeated injections of SLE-LDL, LPC or PAF to apoE^-/- mice led to increases in IMT, collagen deposition, fatty-streak areas in the aortic wall, and cell senescence in the aortic endothelium.

Figure 2. LPC and PAF were increased in SLE-LDL and L5.

SLE-L5 induces CD16+ expression in monocytes and monocyte adhesion to ECs through CX3CL1-CX3CR1 interactions.

Flow cytometric analysis showed that SLE-L5 lipids, but not SLE-L1 lipids, induced an increase in the percentage of CD16+ monocytes, which are CX3CR1 expressing cells. On the other hand, SLE-LDL induces CX3CL1 expression in activated endothelial cells. Through CX3CL1-CX3CR1 interactions, SLE-L5 induces early atherosclerotic changes in young apoE^-/- mice. SLE-L5 induced significant atherosclerotic lesion formation in the aortic arch of the mice as well as collagen deposition and elastic fragmentation in aortas.

Conclusion

L5 LDL (the most electronegative subfraction) is increased in SLE patients. By mass spectrometry, results showed that L5 LDL is an LPC- and PAF-rich lipoprotein. Through CX3CL1-CX3CR1 interactions between ECs and CD16+ monocytes, L5 LDL promotes atherosclerosis. Our findings suggest that the L5 level, not the total LDL concentration, should be a therapeutic target for preventing EVA and atherosclerosis in patients with SLE.

Graphical Abstract

Application and Highlights:

1.     Through CX3CL1-CX3CR1 interactions between ECs and CD16+ monocytes, L5 LDL promotes atherosclerosis.

2.     An increase in plasma L5 levels, not total LDL concentration, may promote early vascular aging in SLE patients, leading to premature atherosclerosis.

3.     The L5 level should be a therapeutic target for preventing early vascular aging and atherosclerosis in patients with SLE.

Research Team Members:

Liang-Yin Ke, Jeng-Hsien Yen

Representative Department:

Department of Medical Laboratory Science and Biotechnology, College of Health Sciences

Introduction of Research Team:

Liang-Yin Ke (from the Department of Medical Laboratory Science and Biotechnology), Jeng-Hsien Yen (from Graduate Institute of Medicine), the first author Hua-Chen Chan (Center for Lipid Biosciences) and colleagues published the above-named paper in the Arthritis & Rheumatology this year. Immediately, the paper got great attention. The editor of Nature Reviews, Joanna Clarke, interviewed with the corresponding authors, and later she wrote a “research highlight” editorial and published in Nature Reviews Rheumatology, entitled as “LDL subfraction linked to vascular aging and heart disease in SLE.”

Contact Email: kly@gap.kmu.edu.tw

Publication: Arthritis Rheumatol. 2020 Jun;72(6):972-984.

Full-Text

Article: https://onlinelibrary.wiley.com/doi/epdf/10.1002/art.41213