Mini-Reviews in Organic Chemistry - Volume 18, Issue 7, 2021

In this brief review, we consider the generation of free radicals by irradiation with UVlight solutions of compounds with weak chemical bonds. Bond Dissociation Energies (BDE) are compared with the energies of photons. Light sources used in industry and academia are listed in this article. Free radicals can be produced by photodissociation and by bimolecular chemical reactions between the electronically- excited state of a molecule and a quencher. Important examples are presented. A special effort is devoted to Light-Emitting Diodes (LED) which gained a wide application in this century. We cited books on free radicals and photochemistry as an introduction, as well as recent publications dated 2020.

Activated peroxide systems are formed by adding so-called bleach activators to an aqueous solution of hydrogen peroxide, developed in the seventies of the last century for use in the domestic laundry for their high energy efficiency and introduced at the beginning of the 21st century to the textile industry as an approach toward overcoming the extensive energy consumption in bleaching. In activated peroxide systems, bleach activators undergo perhydrolysis to generate more kinetically active peracids that enable bleaching under milder conditions while hydrolysis of bleach activators and decomposition of peracids may occur as side reactions to weaken the bleaching efficiency. This mini-review aims to summarize these competitive reactions in activated peroxide systems and their influence on bleaching performance.

Pandemic, COVID-19 came into existence in late December 2019 at Wuhan, China. To cure the COVID-19 and reduction in morbidity, the development of potential vaccines and antiviral drugs may take months or years. To reduce the pressure on healthcare infrastructure, traditional medicines may use as an alternative measure. The rationale of the current study was to provide the pharmacological details of Ayurvedic herbs viz. Alstonia scholaris L., Picrorhiza kurroa, Swertia chirata and Caesalpinia crista w.r.t. symptoms of COVID-19. The available information on the ethnomedicinal uses, phytochemistry, and pharmacology was collected via a library and electronic searches in Sci-Finder, Pub-Med, Science Direct, Google Scholar for the period of up to 31 August 2020. The major symptoms of COVID-19 include pro-inflammation, inhibition of Angiotensin-Converting Enzyme II (ACE2) and reactive oxygen species. A literature search revealed that all herbs under study are potent against two or more symptoms of COVID-19. All four Ayurvedic herbs viz. Alstonia scholaris L., Picrorhiza kurroa, Swertia chirata and Caesalpinia crista may be a good option, including other traditional drugs during the outbreak of COVID-19. In-depth experimental, preclinical and clinical studies are required in the future to develop a potent drug against COVID-19.

Lignin, one of the major components of lignocellulosic materials, is the largest natural source of aromatic building blocks on the planet having high service potential for producing valuable chemicals and fuels. It is surrounded by an extensive network of hemicellulose and cellulose in lignocelluloses such as agricultural residues, processing by-products, forestry residues, etc. Therefore, its extraction needs proper procedures, which have been researched worldwide in the past few decades. Lignin is a complex phenolic polymer with hydroxycinnamyl alcohols i.e. p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol as its monomers. Also, lignin based phenolic acids i.e. substituted hydroxycinnamic acids such as p-coumaric acid, ferulic acid, caffeic acid, syringic acid, are core structural moieties in various drug categories such as antimicrobial, anti-­128;inflammatory, analgesic, anti- tyrosinase, antihistamine, antirheumatic and anti-thrombosis agents. Therefore, differently substituted hydroxycinnamic acids isolated from lignin have been explored recently with a view of dual advantage of valorization of unavoidable wastes; and exploiting drugs, which would probably have no harmful side effects because of their natural origin. In this review, recent research findings on the extraction of lignin followed by classification of natural phenolic acids, isolation of substituted hydroxycinnamic acids from lignin and their derivatization for various bioactive properties are discussed.

Thiol-containing amino acids and peptides play crucial roles in many physiological processes. For example, Cysteine (Cys) and Homocysteine (Hcy) are considered to be related to a number of health disorders, such as renal failure, AIDS, Alzheimer’s and Parkinson’s diseases, atherosclerotic cardiovascular diseases, neural tube defects, and coronary heart disease. Glutathione (GSH), an important tripeptide with a thiol group, performs vital biological functions that are involved in combating oxidative stress and maintaining redox homeostasis. Cysteine also plays important roles in our bodies as an antioxidant, a metal cofactor binder in enzymes, and a protein structure stabilizer by disulfide bond formation in the proteins. Hcy is involved in cellular growth and GSH in redox homeostasis. Hence, the rapid, sensitive, and selective detection of such biothiols is of considerable importance and significant interest. Different fluorescent chemosensors have been introduced to develop and improve the detection techniques and accuracy of these biothiols. In this review article, we have presented some research works to show a guiding principle for the design of effective chemosensors that are highly sensitive and selective for the detection of a particular group of biothiols in an aqueous medium. In line with these developments, the researchers have developed novel chemosensors that signal the binding events of these above-mentioned biothiols through their optical properties. The binding mechanism and properties have also been established with different theoretical studies. Their applications in the form of colorimetric kits, logic gates, live-cell imaging, and quantification from different biological samples have also been developed.

Historically, the use of Iodinated Contrast Media (ICM) for diagnostic purposes, particularly radiography and Computed Tomography (CT), is well-known. Many of the ICM are included in the World Health Organization (WHO)’s List of Essential Medicines. Depending on the chemotype and the presence of ionizable functional group(s), the ICM are categorized into the ionic/nonionic monomers/dimers. The lipophilicity, aqueous solubility, viscosity and osmolality are major characteristics dictating their use for one procedure versus the other. Over the last several decades, substantial advancement has occurred in the design and development of novel ICM, solely to reduce their propensity to cause adverse effects. Given the nature of their acute usage, some of the agents with appreciable toxicity are still used. Understanding their chemistry aspects is crucial to appreciate, acknowledge and justify the usage of these extremely important torch-bearers of the diagnostic agent’s class. The present review article presents an in-depth overview of the synthetic methods, therapeutic indications, potential adverse effects along with the commercial and environmental aspects of ICM. The safety and tolerability of these agents is a field that has gained significant importance, which is given due importance in the discussion.

Transition-metal-catalyzed C−H bond activation employing a directing group has been shown to be a powerful tool to access C−C or C−hetero bond formation. Oxygen and nitrogen atoms are commonly applied as the electron donor for these directing groups. In contrast, there are only a few studies on sulfur-containing groups, probably due to their toxicity to transition-metal catalysts. Nowadays, a large amount of C−H activation reactions directed by sulfur-containing auxiliary groups have been successfully achieved. As these groups can be facilely removed or modified in situ or in further steps, they are of great value in creative synthetic strategies. This paper reviews recent advances in the studies using thioether, thiol/thiophenol/disulfide, sulfoxide, and thiocarbonyl as directing groups for intermolecular C−H functionalizations as well as intramolecular oxidative annulations.

Drug discovery research focuses on the Rational Drug Design (RDD) concepts, and the major obstacles in the drug discovery process are the lack of target specificity and selectivity. The realization of higher target selectivity of peptide drugs has promoted peptide research. Rapid growth in genomics along with recombinant DNA (rDNA) technology and gene expression studies stimulated the peptide research. The promising use of peptide therapeutics demands sensitive and selective quantification methods. Protein sequencing and proteomic investigations can be successfully accomplished through the Mass Spectroscopy (MS) based methods. Mass spectroscopy-based soft ionization methods, namely, electrospray ionization (ESI) and Matrix-Assisted Laser Desorption/Ionization (MALDI), offer high-throughput sequencing to provide the characterization (sequence and structure) of intact proteins/peptides. The advent of tandem Mass Spectrometry (MS/MS) along with data acquisition methods are the basis for the evolution of peptide therapeutics research. The evolution of data science helped in developing computational proteomics, which assists in the quantitative determination of protein samples. This review narrates the role of mass spectrometry in the peptide drug discovery particularly in the sequence characterization along with the latest developments, such as computational proteomics.

To obtain the different types of technical utilities, the surface of various systems needs to be modified by altering surface properties using polymer coating(s) which is one of the emerging technologies to impart smart functions. The polymer coating has a wide application in various fields such as biomedicals, pharmaceuticals, packaging, corrosion control, electronics, and abrasion control. The coating can be done using both biodegradable and non-degradable polymers having eminent properties such as better mechanical strength, anti-wear characteristics, corrosion protection, electrical conductivity, biocompatibility, and high surface functionality. Several methods have been reported for the fabrication of defensive coatings. A thoughtful selection of polymers, coating methods, and critical process parameters may bring forth a better protective coating with advanced properties. This review discusses the objectives of the polymer coating, various coating technologies, and their smart applications.

Supramolecular compounds are capable of undergoing various non-covalent interactions with other molecules like host-guest chemistry, controlled encapsulation, hydrophobic interactions, a variety of delivering strategies, electron affinity induced interactions, etc. These properties of supramolecular compounds make them attractive to be effective drug carriers. This review will describe in detail the recent interesting reports on the structure-activity relationship of supramolecular compounds in drug delivery. The supramolecular compounds considered are cyclodextrins, cucurbiturils, avidin, biotin, rotaxanes, viologens, and dendrimers. Studying the opportunities given by these supramolecular compounds in drug delivery will pave the way for novel efficient drug delivery systems for the future.