Vadde Ravinder

Ru(II) complexes of N4 and N2O2 macrocyclic Schiff base ligands: Their antibacterial and antifungal studies

Reactions of [RuCl2(DMSO)4] with some of the biologically active macrocyclic Schiff base ligands containing N4 and N2O2 donor group yielded a number of stable complexes, effecting complete displacement of DMSO groups from the complex. The interaction of tetradentate ligand with [RuCl2(DMSO)4] gave neutral complexes of the type [RuCl2(L)] [where L=tetradentate macrocyclic ligand]. These complexes were characterized by elemental, IR, 1H, 13C NMR, mass, electronic, thermal, molar conductance and magnetic susceptibility measurements. An octahedral geometry has been proposed for all complexes. All the macrocycles and macrocyclic Ru(II) complexes along with existing antibacterial drugs were screened for antibacterial activity against Gram +ve (Bacillus subtilis, Staphylococcus aureus) and Gram -ve (Escherichia coli, Klebsiella pneumonia) bacteria. All these compounds were found to be more active when compared to streptomycin and ampicillin. The representative macrocyclic Schiff bases and their complexes were also tested in vitro to evaluate their activity against fungi, namely, Aspergillus flavus and Fusarium species.

Antimicrobial study of newly synthesized 6-substituted indolo[1,2-c]quinazolines

A new series of indolo[1,2-c]quinazoline derivatives were prepared in good yield through reaction of 2-(o-aminophenyl)indole with a variety of arylaldehydes. The structures of the newly synthesized compounds were confirmed by IR, (1)H NMR, (13)C NMR and mass spectral studies and elemental analysis. All the title compounds were investigated for their activity against certain strains of Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis and Streptococcus pyogenes), Gram-negative bacteria (Salmonella typhimurium, Escherichia coli and Klebsiella pneumonia) and pathogenic Fungi (Aspergillus niger, Candida albicans and Trichoderma viridae). Ampicillin and ketoconazole were used as reference compounds. The results revealed that some of synthesized compounds displayed marked activity against all the tested microorganisms.

Mono and bis-6-arylbenzimidazo[1,2-c]quinazolines: a new class of antimicrobial agents.

With the aim of obtaining novel biologically active compounds, we have synthesized a series of mono, bis-2-o-arylideneaminophenylbenzimidazoles and a second series of corresponding mono, bis-6-arylbenzimidazo[1,2-c]quinazolines respectively. The target benzimidazo[1,2-c]quinazoline compounds were obtained by the condensation of 2-(o-aminophenyl)benzimidazole with mono and di carbonyl compounds, followed by oxidative cyclisation of the resulting mono and bis-2-o-arylideneaminophenylbenzimidazoles.All the products were characterized via IR, (1)H NMR, (13)C NMR, MS and elemental analysis. The antimicrobial activities of all quinazolines against various bacteria and fungi were evaluated. Among the compounds tested IVd, IVe exhibited good antibacterial and antifungal activities while IIIb, IIIc also showed notable antimicrobial activity with reference to standard drugs Ampicillin and Ketoconazole respectively.

Binuclear cobalt(II), nickel(II), copper(II) and palladium(II) complexes of a new Schiff-base as ligand: synthesis, structural characterization, and antibacterial activity.

A binucleating new Schiff-base ligand with a phenylene spacer, afforded by the condensation of glycyl-glycine and o-phthalaldehyde has been served as an octadentate N₄O₄ ligand in designing some binuclear complexes of cobalt(II), nickel(II), copper(II), and palladium(II). The binding manner of the ligand to the metal and the composition and geometry of the metal complexes were examined by elemental analysis, conductivity measurements, magnetic moments, IR, ¹H, ¹³C NMR, ESR and electronic spectroscopies, and TGA measurements. There are two different coordination/chelation environments present around two metal centers of each binuclear complex. The composition of the complexes in the coordination sphere was found to be [M₂(L)(H(2)O)₄] (where M=Co(II) and Ni(II)) and [M₂(L)] (where M=Cu(II) and Pd(II)). In the case of Cu(II) complexes, ESR spectra provided further information to confirm the binuclear structure and the presence of magnetic interactions. All the above metal complexes have shown moderate to good antibacterial activity against Gram-positive and Gram-negative bacteria.

Physicochemical and biological characterization of novel macrocycles derived from o-phthalaldehyde

A series of novel macrocyclic compounds were synthesized by the condensation of o-phthalaldehyde with aromatic amino alcohols followed by treatment with 1,2-dibromoethane or 1,3-dibromopropane in non-template method. The structural features of the isolated macrocycles have been determined from the microanalytical, IR, (1)H, (13)C NMR and mass spectral studies. Antimicrobial activities of these macrocyclic compounds were tested against the gram-positive (Bacillus subtilis, Staphylococcus aureus) and gram-negative (Escherichia coli, Klebsiella pneumoniae) bacteria and found to exhibit potential antibacterial activity. The macrocycles were also tested in vitro to evaluate their activity against fungi, namely, Aspergillus flavus (A. flavus) and Fusarium species.

Synthesis and antimicrobial activities of a new class of 6-arylbenzimidazo[1,2-c]quinazolines

13 C NMR, MS and elemental analysis. The antimicrobial activities of all 6-arylbenzimidazo (1,2-c)quinazolines against three Gram-positive (S. aureus, B. subtilis, S. pyogenes), three Gram-negative (S. typhimurium, E. coli, K. pneumonia) bacteria and three fungal strains (A. niger, C. albicans, T. viridae) were evaluated. Among the compounds tested 13, 19 and 20 showed most potent inhibitory action against test organisms.

6-substituted indolo[1,2-c]quinazolines as new antimicrobial agents.

A series of 2‐o‐arylidineaminophenylindoles and their cyclic derivatives (indolo[1,2‐c]quinazolines) were synthesized. The reactions occurred under relatively mild conditions and afforded the desired product in good yields. Molecular structures of the synthesized compounds were confirmed by IR, 1H‐NMR, 13C‐NMR, MS spectra, and elemental analyses. Furthermore, all the final products were screened for in‐vitro antibacterial activity against three Gram‐positive and three Gram‐negative bacteria and also tested for their inhibitory action against three strains of fungi. Compound IIc showed potent activity against all the bacterial (except S. typhimurium) and fungal strains. Especially, compounds IIi and IIj which have isoquinolyl and pyridyl substituents displayed potent antibacterial as well as antifungal activities compared to those of the respective standard drugs Ampicillin and Ketoconazole.

Synthesis, Spectral and Antibacterial Studies of Copper(II) Tetraaza Macrocyclic Complexes

A novel family of tetraaza macrocyclic Cu(II) complexes [CuLX2] (where L = N4 donor macrocyclic ligands) and (X = Cl−, NO3 −) have been synthesized and characterized by elemental analysis, magnetic moments, IR, EPR, mass, electronic spectra and thermal studies. The magnetic moments and electronic spectral studies suggest square planar geometry for [Cu(DBACDT)]Cl2 and [Cu(DBACDT)](NO3)2 complexes and distorted octahedral geometry to the rest of the ten complexes. The biological activity of all these complexes against gram-positive and gram-negative bacteria was compared with the activity of existing commercial antibacterial compounds like Linezolid and Cefaclor. Six complexes out of twelve were found to be most potent against both gram-positive as well as gram-negative bacteria due to the presence of thio group in the coordinated ligands.

Microwave-assisted, ruthenium-catalyzed intramolecular amide-alkyne annulation for the rapid synthesis of fused tricyclic isoquinolinones

Microwave irradiation strongly accelerates the ruthenium(II)-catalyzed intramolecular annulation of alkyne appended benzamides to generate the fused tricyclic isoquinolinone scaffolds through a domino C–C and C–N bond formation by C–H and N–H activation, which is very useful for the synthesis of several analogues of tricyclic isoquinolinone alkaloids. The reaction proceeds with high functional group tolerance to furnish the products in good to high yields.

Synthesis of some new mono, bis-indolo[1, 2-c]quinazolines: evaluation of their antimicrobial studies

A convenient three-step strategy is proposed for the synthesis of mono and bis-indolo[1,2-c] quinazolines from 2-(2-aminophenyl)indole and various aryl aldehydes. The newly synthesized compounds were characterized by elemental analysis, IR, 1H NMR, 13C NMR, and mass spectroscopic investigation. All the derivatives were screened for antibacterial (S. aureus, B. subtilis, S. pyogenes, S. typhimurium, E. coli, K. pneumonia) and antifungal (A. niger, C. albicans, T. viridae) activities by cup plate method. Among the compounds tested, mono- indolo[1,2-c] quinazolines (15-18) exhibited good antibacterial activities while 15 and 18 also showed notable antifungal activity. Especially, 19 and 20 exhibited stronger antibacterial as well as antifungal activity against all tested strains.