A novel and efficient method for the synthesis of α-ketoamides, employing a dimethyl sulfoxide (DMSO)-promoted oxidative amidation reaction between 2-oxoaldehydes and amines under metal-free conditions is presented. Furthermore, mechanistic studies supported an iminium ion-based intermediate as a central feature of reaction wherein C1-oxygen atom of α-ketoamides is finally derived from DMSO.

Marine invertebrates are a rich source of novel, bioactive secondary metabolites and have attracted a great deal of attention from scientists in the fields of chemistry, pharmacology, ecology, and molecular biology. This profilic natural source has produced several antitumor secondary metabolites and amongst these, indole alkaloids are of wide occurrence. Meridianins A-G (1-7) are indole alkaloids isolated from tunicate Aplidium meridianum and are known to inhibit variety of protein kinases associated with cancer and neurodegenerative diseases. These compounds also exhibited promising antiproliferative activity in several cancer cell lines. Amongst natural meridianins, meridianin E (5) showed potent and selective inhibition of CDK-1 and CDK-5. Several synthetic meridianin analogs exhibited potent and selective inhibition of glycogen synthase-3 (GSK-3) and dual-specificity tyrosine-phosphorylation regulated kinase 1A (Dyrk-1A) which are known to be implicated in progression of Alzheimer's disease. The present review provides the critical account of isolation, medicinal chemistry and pharmacology of meridianins. Our analysis of the structure-activity relationships of this family of compounds highlights the existence of various potential leads for the development of novel anticancer and anti-Alzheimer's agents.

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Given the attractive ability of iminium ions to functionalize molecules directly at ostensibly unreactive positions, the reactivity of iminium ions, in which an α CH2 group is replaced by CO was explored. Background studies on the ability of such iminium cations to promote reactions via an iminium-catalyzed or iminium-equivalent pathway are apparently unavailable. Previously, tandem cross-coupling reactions were reported, in which an iminium ion undergoes nucleophilic 1,2-addition to give a putative three-component intermediate that abstracts a proton in situ and undergoes self-deamination followed by unprecedented DMSO/aerobic oxidation to generate α-ketoamides. However, later it was observed that iminium ions can generate valuable α-ketoamides through simple aerobic oxidation. In all reactions, iminium ions were generated in situ by reaction of 2-oxoaldehydes with secondary amines.

An efficient one-pot multi-component synthesis of flavans using perchloric acid supported on silica as a recyclable heterogeneous catalyst has been described. This is the first report of direct one-step construction of a flavan skeleton from a phenolic precursor. The method involves a Knoevenagel-type condensation leading to in situ formation of transient O-quinone methide which further undergoes [4 + 2]-Diels-Alder cycloaddition with styrene to yield a flavan skeleton. The method provides easy access to a wide range of bio-active natural products viz. flavonoids, anthocyanins and catechins.

An efficient functional group induced strategy for the synthesis of 6-aminophenanthridines (6AP) has been developed as a result of an in situ generated novel system "CO-CH(N1N2)". This reaction presents a new mode of N2 extrusion in benzotriazoles that later result in decarbonylative cyclization to 6AP. This method offers an easier protocol for the synthesis of 6AP from readily available inexpensive substrates.

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