Current Organic Chemistry - Volume 24, Issue 4, 2020

The main goal of this review is to summarise the most recent progress in the electrochemical synthesis of copolymers from conjugated co-monomers. The main approaches to electrochemical copolymerisation are highlighted and various trends in the development of new copolymer materials and the intended directions of their applications are explored. The article includes a discussion of various Authors’ approaches to investigate the structure of the obtained products, indicating the key points of interest and the importance of comprehensive identification of the products of electrochemical polymerisation.

Marine natural products (MNPs) containing pyrone rings have been isolated from numerous marine organisms, and also produced by marine fungi and bacteria, particularly, actinomycetes. They constitute a versatile structure unit of bioactive natural products that exhibit various biological activities such as antibiotic, antifungal, cytotoxic, neurotoxic, phytotoxic and anti-tyrosinase. The two structure isomers of pyrone ring are γ- pyrone and α-pyrone. In terms of chemical motif, γ-pyrone is the vinologous form of α- pyrone which possesses a lactone ring. Actinomycete bacteria are responsible for the production of several α-pyrone compounds such as elijopyrones A-D, salinipyrones and violapyrones etc. to name a few. A class of pyrone metabolites, polypropionates which have fascinating carbon skeleton, is primarily produced by marine molluscs. Interestingly, some of the pyrone polytketides which are found in cone snails are actually synthesized by actinomycete bacteria. Several pyrone derivatives have been obtained from marine fungi such as Aspergillums flavus, Altenaria sp., etc. The γ-pyrone derivative namely, kojic acid obtained from Aspergillus fungus has high commercial demand and finds various applications. Kojic acid and its derivative displayed inhibition of tyrosinase activity and, it is also extensively used as a ligand in coordination chemistry. Owing to their commercial and biological significance, the synthesis of pyrone containing compounds has been given attention over the past years. Few reviews on the total synthesis of pyrone containing natural products namely, polypropionate metabolites have been reported. However, these reviews skipped other marine pyrone metabolites and also omitted discussion on isolation and detailed biological activities. This review presents a brief account of the isolation of marine metabolites containing a pyrone ring and their reported bio-activities. Further, the review covers the synthesis of marine pyrone metabolites such as cyercene-A, placidenes, onchitriol-I, onchitriol-II, crispatene, photodeoxytrichidione, (-) membrenone-C, lihualide-B, macrocyclic enol ethers and auripyrones-A & B.

Privileged scaffolds are ubiquitous as effective templates in drug discovery regime. Natural and synthetically derived hybrid molecules are one such attractive scaffold for therapeutic agent development due to their dual or multiple modes of action, minimum or no side effects, favourable pharmacokinetics and other advantages. Coumarins and chalcone are two important classes of natural products affording diverse pharmacological activities which make them ideal templates for building coumarin-chalcone hybrids as effective biological scaffold for drug discovery research. Provoked by the promising medicinal application of hybrid molecules as well as those of coumarins and chalcones, the medicinal chemists have used molecular hybridisation strategy to report dozens of coumarin- chalcone hybrids with a wide spectrum of biological properties including anticancer, antimicrobial, antimalarial, antioxidant, anti-tubercular and so on. The present review provides a systematic summary on synthetic strategies, biological or chemical potential, SAR studies, some mechanisms of action and some plausible molecular targets of synthetic coumarin-chalcone hybrids published from 2001 till date. The review is expected to assist medicinal chemists in the effective and successful development of coumarin- chalcone hybrid based drug discovery regime.

This review summarizes the synthesis, reactions, and biological activities of tetrazolo[1,5-a]quinoline derivatives. These derivatives were synthesized by several methods such as i) from the reaction of 2-chloroquinoline with sodium azide ii) from diazotization 2-hydrazinylquinoline derivatives, and iii) from intramolecular cyclocondensation of 2-azidoarylidenes. Also, the chemical reactions and pharmacological activities of some tetrazoloquinolines such as tetrazolo[1,5-a]quinoline-4-carbaldehyde, 5-chlorotetrazolo[ 1,5-a]quinoline, 4-(chloromethyl)tetrazolo[1,5-a]quinoline, tetrazolo[1,5- a]quinoline-4-carboxylic acid, and 5-azidotetrazolo[1,5-a]quinoline were discussed.

The phospha-Brook rearrangement of dialkyl 1-aryl-1-hydroxymethylphosphonates (HPs) to the corresponding benzyl phosphates (BPs) has been elaborated under solid-liquid phase transfer catalytic conditions. The best procedure involved the use of triethylbenzylammonium chloride as the catalyst and Cs2CO3 as the base in acetonitrile as the solvent at room temperature. The substrate dependence of the rearrangement has been studied, and the mechanism of the transformation under discussion was explored by quantum chemical calculations. The key intermediate is an oxaphosphirane. The one-pot version starting with the Pudovik reaction has also been developed. The conditions of this tandem transformation were the same, as those for the one-step HP→BP conversion.