Azafluorene derivatives as inhibitors of SARS CoV-2 RdRp: Synthesis, physicochemical, quantum chemical, modeling and molecular docking analysis

The crystal structures of 2-(1H-indol-3-yl)-4-phenyl-5H-indeno [( Cheng et al., 2007; Lee et al., 2003) 1,21,2-b]pyridine-3-carbonitrile (Ia) and 2-(1H-indol-3-yl)-4-(4-methoxyphenyl)-5H-indeno [( Cheng et al., 2007; Lee et al., 2003) 1,21,2-b]pyridine-3-carbonitrile (Ib) were determined using single crystal X-ray diffraction. Both the compounds belong to the triclinic system with the P-1 space group. The azafluorene ring system in both the compounds is effectively planar. The intermolecular interactions present in the compounds are discussed using Hirshfeld surface analysis, QTAIM and NCI. Compound Ib formed a strong interaction (−24.174 kJ/mol) with the solvent molecule. Both the compounds were geometry optimized using DFT/B3LYP level of theory. The compound’s drug-like behaviors were studied using HOMO-LUMO analysis. The homology modeling of SARS CoV-2 RdRp was done utilizing the PDB 6NUR_A as a template. The model showed above 99% similarity with its preceder SARS CoV. The molecular docking analysis of the synthesized compounds was carried out along with some suggested drugs for COVID-19 and some phytochemicals. The docking results were then analyzed. The binding free energy of the complexes were calculated using MM-PB(GB)SA and ADMET properties of Ia and Ib were also predicted. Some suggestions are given from this analysis.

Ethyl 6′-cyano-7′-(p-tolyl)-1′,6′,7′,7a′-tetrahydro-3′H-spiro[indeno[1,2-b]quinoxaline-11,5′-pyrrolo[1,2-c]thiazole]-6′-carboxylate

The title compound, C31H26N4O2S, crystallizes in a triclinic centrosymmetric lattice with two molecules in the unit cell. The five-membered thiazole and pyrrolidine rings adopt twisted and envelope conformations, respectively. The methoxyphenyl and indenoquinoxaline planes are oriented with a dihedral angle of 88.1 (1)° to each other. The crystal structure features C—H...N, C—H...O and C—H...S intermolecular interactions forming two R 2 2(16) ring motifs and a C(11) and two C 2 2(14) chain motifs. The –CH3 group of the ethyl side chain is disordered over two positions with site occupancies of 0.55 and 0.45.

Synthesis of indole-cycloalkyl[b]pyridine hybrids via a four-component six-step tandem process

The one-pot four-component reaction of 3-(1H-indol-3-yl)-3-oxopropanenitriles, aromatic aldehydes, cycloalkanones and ammonium acetate occurred via a six-step tandem Knoevenagel condensation–nucleophilic addition to carbonyl–Michael addition–N-cyclization–elimination–air oxidation sequence to afford structurally intriguing indole–cycloalkyl[b]pyridine-3-carbonitrile hybrid heterocycles in excellent yields.

6′-(3-Bromophenyl)-7′-nitro-1′,6′,7′,7a'-tetrahydro-3′H-spiro[indeno[1,2-b]quinoxaline-11,5′-pyrrolo[1,2-c]thiazole]

The title compound, C26H19BrN4O2S, crystallizes in a monoclinicC-centred lattice with eight molecules in the unit cell. The five-membered thiazole and pyrrolidine rings adopt envelope conformations and the bromophenyl and indenoquinoxaline planes are oriented at a dihedral angle of 61.6 (1)° to each other. The molecular structure features an intramolecular C—H...N interaction leading to anS(6) ring motif.C(9) andC(10) chains along thec- andb-axis directions form through C—H...Br and C—H...S contacts, respectively. In addition, C—H...O and C—H...N hydrogen bonds form inversion dimers withR22(10) andR22(14) motifs, respectively. One O atom is disordered over two positions (occupancy ratio 0.63:0.37).

7′-Nitro-6′-phenyl-1′,6′,7′,7a′-tetrahydro-spiro[indeno[1,2-b]quinoxaline-11,5′-pyrrolo[1,2-c][1,3]thiazole]

In the title compound, C26H20N4O2S, the thiazole and pyrrolidine rings adopt envelope conformations with the respective flap atoms being the N atom and the nitro-bearing C atom. The phenyl and indenoquinoxaline planes are oriented at an angle of 66.72 (1)° to each other. The molecular structure features two intramolecular interactions,viz. C—H...N and C—H...O. In the crystal, the molecules are connected through C—H...N and C—H...O interactions, forming ring motifs [twoR21(7),R22(14),R22(22) andR22(16)]. These ring motifs are connected through aC(9) motif chain.

A One-Pot Multicomponent 1,3-Dipolar Cycloaddition Strategy: Combinatorial Synthesis of Dihydrothiophenone-Engrafted Dispiro Hybrid Heterocycles

The combinatorial syntheses of a library of novel dihydrothiophenone-engrafted dispiro oxindole/indenoquinoxaline-pyrrolidine/pyrrolothiazole/indolizine hybrid heterocycles have been realized through a chemo-, regio-, and stereoselective multicomponent 1,3-dipolar cycloaddition strategy.

Multicomponent Dipolar Cycloaddition Strategy: Combinatorial Synthesis of Novel Spiro-Tethered Pyrazolo[3,4-b]quinoline Hybrid Heterocycles

The stereoselective syntheses of a library of novel spiro-tethered pyrazolo[3,4-b]quinoline-pyrrolidine/pyrrolothiazole/indolizine-oxindole/acenaphthene hybrid heterocycles have been achieved through the 1,3-dipolar cycloaddition of azomethine ylides generated in situ from α-amino acids and 1,2-diketones to dipolarophiles derived from pyrazolo[3,4-b]quinoline derivatives.

Dermatoglyphic fluctuating asymmetry and symmetry in familial and non familial schizophrenia

Three dermatoglyphic traits, viz; finger patterns, finger ridge counts, and palmer a-b ridge counts of 57 (M-29; F-28) and 64 (M-29; F-35). Schizophrenics with and without positive family history respectively, and 65 controls (M-30, F-35), were analysed to determine their level of fluctuating asymmetry.Uniformly higher fluctuating asymmetry was observed in the loop ridge counts of second digits of males and females of both the groups of schizophrenics. Significantly increased symmetry in the right and left loop ridge counts in the fifth digits of the family history positive female patients was noted. Barring the family history positive female schizophrenics, the rest of the patient groups manifested higher fluctuating asymmetry in their right and left whorl ridge counts of fourth digits. Family history positive patients of both sexes and female patients with negative family history displayed higher fluctuating asymmetry in the right and left palmer a-b ridge counts.

Spectrophotometric determination of phosphine residues in rice

Phosphine residues were determined in 2 types of rice samples, raw polished and parboiled. The yellow chromophore due to phosphine from raw polished rice had 2 absorption maxima, a strong one at 370-380 nm and a weaker one at 400-410 nm. The chromophore from parboiled rice also had 2, one at 390-400 nm and the other at 410-420 nm. A closed system containing rice and a phosphine tablet or powder yielded 93-99% recovery of fortified phosphine. At any given dose of phosphine, parboiled rice retained a higher amount of residue after aeration than did raw polished rice.

Effect of acrylonitrile on trehalase, phosphorylase and acetylcholinesterase activities in Tribolium castaneum Herbst and Trogoderma granarium Everts

Acrylonitrile inhibited trehalase and phosphorylases in larvae and adults of Tribolium castaneum. In Trogoderma granarium larvae phosphorylases alone were inhibited. Acetylcholinesterase was not affected.

Colorimetric method for the determination of ethylene dibromide residues in grains and air

A method based on the hydrolytic debromination of ethylene dibromide (EDB) in the presence of an oxidizing agent has been developed. Bromine liberated from inorganic bromide is used to brominate p-rosaniline. The intensity of the resulting violet-red bromo compound in chloroform is measured at 580 nm. The relationship between absorbance and concentration of EDB is linear in the range of 5-60 mug. The method is very sensitive and as little as 0.50 ppm unchanged EDB residue in a 20 g sample of fumigated grain and 1 ppm EDB in a 10 ml air sample can be detected.