Recent advances on heterocyclic compounds with antiviral properties

Chemistry of Heterocyclic Compounds - In recent years several important viral infections have emerged and antiviral chemotherapeutic agents are not sufficiently effective in clinic, leading to...     

Microwave‐Assisted Synthesis and Antituberculosis Screening of Some 4‐((3‐(Trifluoromethyl)‐5,6‐dihydro‐[1,2,4]triazolo[4,3‐a]pyrazin‐7(8H)‐l)methyl)benzenamine Hybrids

In the present investigation, a series of 4‐((3‐(trifluoromethyl)‐5,6‐dihydro‐[1,2,4]triazolo[4,3‐a]pyrazin‐7(8H)‐yl)methyl)benzenamine analogs 6a–o were synthesized and characterized by IR, NMR (¹H and ¹³C), and mass spectra. All newly synthesized compounds 6a–o were prepared under conventional and microwave irradiation methods. These compounds obtained in higher yields and in shorter reaction times in the microwave irradiation method when compared with the conventional method. Synthesized compounds 6a–o were inspected for their in vitro antitubercular activity against Mycobacterium tuberculosis H₃₇Ra using an established XTT reduction menadione assay. Among the screened compounds, 6i (IC₅₀: 1.82 μg/mL), 6j (IC₅₀: 1.02 μg/mL), and 6k (IC₅₀: 1.59 μg/mL) showed excellent activity. Furthermore, compound 6i showed MIC₉₀ value of 16.02 μg/mL. In summary, the results indicate the identification of some novel, selective, and specific inhibitors against M. tuberculosis that can be explored further for the potential antitubercular drug.     

Kinetics and mechanism of the anation of (αβ)-hydroxo(tetraethylenepentamine)cobalt(III) by thiosulfate, the base hydrolysis of the (sulfur-bonded) thiosulfato(tetraethylenepentamine)-cobalt(III) and photochemistry of oxygen and sulfur-bonded thiosulfato complexes

Summary The reaction of ()-(tetren)CoOH²⁺ with S₂O ₃ ^2- in the 7.25–8.28 pH range at 20–40 °C yielded S- (yellow) and O- (purple) bonded thiosulfato(tetren)cobalt(III) complexes, the former in larger quantities. The rate determining step is preceded by diffusion-controlled ion-pair [(tetren)CoOH²⁺,S₂O ₃ ^2- ] formation. Replacement of coordinated OH^- by S₂O ₃ ^2- is interpreted in terms of an internal conjugate base mechanism: (tetren)CoOH²⁺ (tetren-H)CoOH ₂ ²⁺ , the reactive amido conjugate base being generated by intramolecular proton transfer from the coordinated NH site.In acid medium the S-bonded (tetren)Co(S₂O₃)⁺ is highly stable to redox decomposition, in contrast to its pentaammine analogue. The complex however, undergoes base hydrolysis yielding the corresponding hydroxo complex. The rate and activation parameters for the base hydrolysis have been reported. Photolysis of O- and S-bonded isomers of [(tetren)CoS₂O₃]⁺ in acidic medium at 254 and 313 nm, respectively, yielded aquation products accompanied by some decomposition of S₂O ₃ ^2- .     

Studies on the thermal stability of iron chromite in air

Studies on the thermal stability of FeCr₂O₄ in air show that surface oxidation preceeds bulk oxidation. Electrical resistivity and thermoelectric power measurements show that above 47 K, Fe²⁺ ions are oxidised by the oxygen adsorbed on the surface and above 523K diffusion of the ions into the bulk occur. DTA and TG show that the bulk oxidation starts above 673 K and the change from the defect spinel phase to the rhombohedral phase occurs during oxidation and is not a sharp transition.

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Zusammenfassung Untersuchungen der thermischen Stabilität von FeCr₂O₄ in Luft zeigen, daß der Masseoxidation eine Oxidation an der Oberfläche vorangeht. Messungen des elektrischen Widerstandes und der thermo-elektromotorischen Kraft zeigen, daß die Fe²⁺-Ionen oberhalb 47 K durch den an der Oberfläche adsorbierten Sauerstoff oxidiert werden und daß oberhalb 523 K eine Diffusion der Ionen in das Innere abläuft. DTA- und TG- Untersuchungen zufolge setzt die Masseoxidation oberhalb 673 K ein und während der Oxidation verläuft ein unscharfer Übergang von der defekten Spinellphase in die rhomboedrische Phase.

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The authors wish to thank DST for some financial help.     

Synthesis of ladder polymers containing polydiacetylene backbones connected with methylene chains and their optical properties

The polymers consisting of polydiacetylene (PDA) backbones were obtained from the novel monomer derivatives, R CC CC R′ CC CC R [where R =  (CH₂)₄OCONHCH₂COOC₄H₉, R′ =  (CH₂)_n ; n = 2, 4, 8] [4BCMU4A(n)], in which linear methylene chain is sandwiched between two diacetylene moieties by solid-state 1,4-addition reaction. The polymerization process was investigated in detail by using spectroscopic techniques such as solid-state ¹³C-NMR, visible absorption, and IR absorption spectra. It was estimated that the polymerization of 4BCMU4A(8) and 4BCMU4A(4) takes place by two consecutive 1,4-addition reactions to form two PDA backbones, which constitute the two poles of the respective ladders. The bridging methylene chain length in the monomer was found to play a vital role as far as the polymerization process is concerned. Thus, the monomers with eight or four methylene units could form the ladder–PDAs by a two-step process, whereas the monomer containing two methylene units could only undergo one-step of 1,4-addition reaction. Further, it was found that the crystallinity of the polymers depends on the methylene chain length in the monomers, 4BCMU4A(8) being the most crystalline of all. These structural features strongly affect their absorption spectra. The third-order nonlinear optical susceptibilities (χ⁽³⁾) for these polymers were measured using third-harmonic generation method. The largest χ⁽³⁾ value obtained was 3.4 × 10⁻¹¹ esu for the poly[4BCMU4A(8)] thin film in resonant region. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3537–3548, 1999     

Synthesis and biological evaluation of novel triazole-biscoumarin conjugates as potential antitubercular and anti-oxidant agents

Research on Chemical Intermediates - The synthesis of a new series of triazole-biscoumarin conjugates by using a molecular hybridization approach is described. The newly synthesized compounds...     

A Halogen-Bond-Driven Artificial Chloride-Selective Channel Constructed from 5-Iodoisophthalamide-based Molecules

Despite considerable emphasis on advancing artificial ion channels, progress is constrained by the limited availability of small molecules with the necessary attributes of self-assembly and ion selectivity. In this study, a library of small molecules based on 5-haloisophthalamide and a non-halogenated isophthalamide were examined for their ion transport properties across the lipid bilayer membranes, and the finding demonstrates that the di-hexyl-substituted 5-iodoisophthalamide derivative exhibits the highest level of activity. Furthermore, it was established that the highest active compound facilitates the selective chloride transport that occurs via an antiport-mediated mechanism. The crystal structure of the compound unveils a distinctive self-assembly of molecules, forming a zig-zag channel pore that is well-suited for the permeation of anions. Planar bilayer conductance measurements proved the formation of chloride selective channels. A molecular dynamics simulation study, relying on the self-assembled component derived from the crystal structure, affirmed the paramount significance of intermolecular hydrogen bonding in the formation of supramolecular barrel-rosette structures that span the bilayer. Furthermore, it was demonstrated that the transport of chloride across the lipid bilayer membrane is facilitated by the synergistic effects of halogen bonding and hydrogen bonding within the channel.