Letters in Organic Chemistry - Volume 21, Issue 11, 2024

The steroidal B-ring 2H-pyran 2 is synthesized by reacting steroidal B-ring α,β- unsaturated ketone 1 and 2-cyano-N-methylacetamide by refluxing for 18 h in methanol in the presence of a catalyst, i.e., chitosan. The product is obtained with a yield of 67%. The structure of the final product 2 is confirmed by utilizing IR, Mass, ¹³C and ¹H NMR spectra. The reaction mechanism of the steroidal pyran ring formation is explored in this paper. The reaction pathway is described by using FMO analysis and relative energies of starting material, intermediate, and transition states, calculated by using the theoretical method, i.e., DFT with B3LYP/6-31G(d). It is found that two intermediates are formed throughout the reaction, which undergo a respective transition state (TS1 and TS2). The energy barrier of each step of the reaction is also calculated. It is also concluded that the reaction is endothermic. The green synthetic method reported in this study would be very useful for the synthetic and medicinal chemists involved in the synthesis of biologically important pyran ring-containing heterocyclic compounds.

In addition to providing a succinct pathway for the stereoselective synthesis of dapoxetine, a potent SSRI employed in the treatment of premature ejaculation, this study highlights the strategic use of Ellman's sulfinamide as a chiral auxiliary. The key method involves the diastereoselective allylation of (S,E)-N-Benzylidenesulfinamide, resulting in the desired S-configuration critical for the pharmacological activity of dapoxetine. The utilization of readily available benzaldehyde as the starting material and 1-naphthol as a late-stage coupling partner contributes to the economic feasibility of the synthesis. Especially, the linear synthetic approach adopted in this study employs simplified and more efficient protocols for various transformations, culminating in an overall yield of 26%. This research not only presents a practical synthetic route for dapoxetine, but also underscores the importance of cost-effective and streamlined methodologies in drug development processes.

An efficient synthesis of Chromeno[b]pyrimidine derivatives 4 has been achieved by treating 4-hydroxy-2H-chromen-2-one 1, furan-2-carbaldehyde / 1H-pyrrole-2-carbaldehyde/ thiophene-2- carbaldehyde 2, and urea/thiourea 3 at 65-70 °C for 90-120 min using 1-Ethyl-3-methylimidazolium acetate as ionic liquid and medium with good yields 86-90%. This synthetic method has numerous advantages, including high yields, a simple protocol, environmental friendliness, brief reaction times, and mild reaction conditions. Using a catalytically active ionic liquid as the medium eliminates the need for a catalyst and a solvent. In this study, the docking score of the synthesized compounds was found to be between -8 to -9 kcal/mol similar to the co-crystal. Additionally, the compounds maintained their amino acid interactions with Tyr 281 (coagulation protein; 6WV3) and Thr 179 (tubulin polymerization protein; 5LYJ.pdb).

The term isatin and its derivative-based MCRs have emerged over the years as a versatile, environment-friendly, and very promising platform for the construction of highly enabling bioactive organic scaffolds such as drugs, natural products, pharmaceuticals etc. In the world of recent advancements, the one-pot strategy based on isatin has come to the forefront of synthetic chemistry for the activation of small organic molecules. This present survey touched on the chemistry of isatin employed over the past decade to sketch and for the creation of various types of organic molecules consisting of heterocyclic or spiro-heterocyclic skeletons via one-pot methodology.

Fireballs are unusual and rare phenomena usually associated with thunderstorms, although sometimes they have been observed during earthquakes, volcano eruptions or in fair weather. There are still questions about their origination, features and interaction with the environment. In this work, a new model is shown to explain the formation of fireballs in fair weather from poplar cotton and peroxides produced by brown-rot fungi. Light emission is produced via thermal decomposition of 1,2- dioxetane phenylcoumarane or 1,2-dioxetane monolignol, from lignin inside the poplar fibers. The energy released during the explosive decaying of fireballs was calculated as being about 3 kilojoules for each gram. This value is the same order of magnitude as the estimated for the explosive fireballs decaying.

Our group recently reported that the polyhydroxy aromatic compound 3,3′,4,4′- biphenyltetrol (2a) is a successful inhibitor of amyloid-β peptide (Aβ) aggregation, decreasing Aβ aggregation by 50 % when present in equimolar concentrations. In the present study, several additional biphenyltetrols were prepared and examined for their in vitro activity against aggregation of Aβ to investigate the effect of the relative positions of hydrogen-bond donors on the aggregation process. Congo red spectral shift assays demonstrated that, of the eight (8) additional biphenyltetrol compounds prepared, three (3) successfully inhibited the association of Aβ monomers, two symmetrical isomers, 2,2′,5,5′-biphenyltetrol (2c), and 2,2′,3,3′-biphenyltetrol (2d), along with one unsymmetrical isomer, 2,3′,4′,5-biphenyltetrol (2g). These results, along with the previously reported results of 2a, strongly suggest that hydroxyl group position affects the ability of the inhibitor to bind to Aβ assemblies, thus impacting inhibitory efficacy.

Novel hydrazones 4, 5, and oxime 6 were produced from the reaction of ketone 3 with hydrazine, phenylhydrazine, and hydroxylamine HCl, respectively. One pot multicomponent reaction of chalcones 7a-c, 3-(1H-indol-3-yl)-3-oxopropanenitrile 8, and ammonium acetate in MeOH at reflux temperature gave 2-(1H-indol-3-yl)-nicotinonitrile derivatives 10-12. Additionally, a one-pot reaction of chalcone 7a, malononitrile or ethyl cyanoacetate, and ammonium acetate in AcOH at reflux temperature afforded 6-aminopyridine derivatives 13 and 14, respectively.

The electron properties of baicalein-family are of great importance in influencing its properties and corresponding bioactivities. In this work, we conducted comprehensive quantum chemistry calculations on pristine baicalein, and its two hydroxyl-substituted derivatives where the hydroxylsubstitution respectively occur at A and C rings. By contrasting with each other, the effects of the hydroxyl-substitution on the electron properties were studied from the aspects of the density of states, molecular orbital, electronic excitation, electrostatic potential, and electron delocalization. According to our computation, the hydroxyl-substitution results in variations in geometry and the consequent electron properties among the discussed molecules. Certainly, this research can contribute to the development of the research on the electron involved properties and the structure-property-activity relationship for the baicalein-family.