Ramendra K. Singh

Rhodium(II) acetate-catalyzed stereoselective synthesis, SAR and anti-HIV activity of novel oxindoles bearing cyclopropane ring

Novel oxindole derivatives bearing substituted cyclopropane ring have been designed on the basis of docking studies with HIV-1 RT using the software DS 2.5 and synthesized as probable NNRTIs against HIV-1 using rhodium(II) acetate-catalyzed stereoselective cyclopropanation reaction. The cyclopropane isomer, having trans relationship with respect to carbonyl of lactam moiety and functional group on the cyclopropane ring, was the major product in all cases along with a small amount of cis and methylene products. The trans isomers interacted well with HIV-1 RT through H-bonding with amino acids, like Lys101, Lys103, His235, Tyr318, constituting the non-nucleoside inhibitor binding pocket (NNIBP) during docking experiments. However, the compounds showed very little activity when subjected to in vitro anti-HIV-1 screening using β-galactosidase assay (TZM-bl cells) and GFP quantification (CEM-GFP cells). The very low level of in vitro HIV inhibition, in comparison to predicted EC(50) values on the basis of computational studies, during CEM-GFP screening using AZT as positive control indicated that probably the HIV RT is not the viral target and the molecules work through some different mechanism.

Synthesis, antibacterial and antiviral properties of curcumin bioconjugates bearing dipeptide, fatty acids and folic acid

Abstract Curcumin bioconjugates, viz. di-O-tryptophanylphenylalanine curcumin (2), di-O-decanoyl curcumin (3), di-O-pamitoyl curcumin (4), di-O-bis-(γ,γ)folyl curcumin (6), C4-ethyl-O-γ-folyl curcumin (8) and 4-O-ethyl-O-γ-folyl curcumin (10) have been synthesized and tested for their antibacterial and antiviral activities. The conjugates 2, 3, 4, 6 and 8 have shown very promising antibacterial activity with MIC ranging between 0.09 and 0.67μM against Gram-positive cocci and Gram-negative bacilli. Further, the conjugates 2, 3, 6, 8 and 10 have been screened for their antiviral activities against HSV, VSV, FIPV, PIV-3, RSV and FHV and the molecules 2 and 3 have shown good results with EC50 0.011μM and 0.029μM against VSV and FIPV/FHV, respectively. However, the molecules did not show expected results against HIV-1 IIIB and ROD strains in MTT assay.

Synthesis and antiviral properties of arabino and ribonucleosides of 1,3-dideazaadenine, 4-nitro-1,3-dideazapurine and diketopiperazine.

Different arabinosides and ribosides, viz. Ara‐DDA or 9(1‐β‐d‐arabinofuranosyl) 1,3‐dideazaadenine (6), Ara‐NDDP or 9(1‐β‐d‐arabinofuranosyl) 4‐nitro‐1,3‐dideazapurine (7), Ara‐DKP or 1(1‐β‐d‐arabinofuranosyl) diketopiperazine (8), Ribo‐DDA or 9(1‐β‐d‐ribofuranosyl) 1,3‐dideazaadenine (9) and Ribo‐NDDP or 9(1‐β‐d‐ribofuranosyl) 4‐nitro‐1,3‐dideazapurine (10) have been synthesized as probable antiviral agents. The arabinosides have been synthesized using the catalyst TDA‐1 that causes stereospecific formation of β‐nucleosides while a one‐pot synthesis procedure was adopted for the synthesis of the ribonucleosides where β‐anomers were obtained in higher yields. All the five nucleoside analogs have been screened for antiviral property against HIV‐1 (IIIB), HSV‐1 and 2, parainfluenza‐3, reovirus‐1 and many others. It was observed that arabinosides had greater inhibitory action than ribosides. The compound 7 or Ara‐NDDP has shown maximum inhibition of HIV‐1 replication than the rest of the molecules with an IC50 of 79.4 µg/mL.

Synthesis and antibacterial evaluation of series of novel tri-substituted-s-triazine derivatives

Two novel series of s-triazine derivatives (6a–e and 7a–f) were synthesized with various aromatic and heterocyclic amines. The synthesized compounds were subsequently evaluated for their in vitro antibacterial activity against three gram-positive viz. Bacillus subtilis (NCIM-2063), Bacillus cereus (NCIM-2156), Staphylococcus aureus (NCIM-2079) and gram-negative bacteria viz. Pseudomonas aeruginosa (NCIM-2036), Escherichia coli (NCIM-2065) and Klebseilla pneumoniae (NCIM-2706) by the broth dilution method as recommended by the National Committee for Clinical Laboratory Standards (NCCLS) using streptomycin as reference standard. Structures of the synthesized compounds were elucidated on the basis of elemental analyses and spectral data.

Antimalarial activity and docking studies of novel bi-functional hybrids derived from 4-aminoquinoline and 1,3,5-triazine against wild and mutant malaria parasites as pf-DHFR inhibitor

Bi-functional conjugates comprised of 4-aminoquinoline and 1,3,5-triazine were synthesized through facile synthetic routes. These compounds were rigorously screened for determination of their antimalarial activity against wild and mutant cultured Plasmodium falciparum. The results disclosed that the conjugates have considerable antimalarial activity against both wild and mutant parasites with marked variation on changing the pattern of substitutions. The observed activity profiles were additionally substantiated by docking studies on both wild and quadruple mutant P. falciparum dihydrofolate reductase thymidylate synthase (pf-DHFR-TS).

4-Aminoquinoline-1,3,5-triazine: Design, synthesis, in vitro antimalarial activity and docking studies

A series of hybrid 4-aminoquinoline 1,3,5-triazine derivatives was synthesized and their chemical structure were confirmed by 1H-NMR, 13C-NMR, FT-IR and mass spectrometric analyses. In vitro antimalarial activity of these compounds was evaluated against chloroquine-sensitive (3D-7) and chloroquine resistant (RKL-2) strains of P. falciparum. Results showed that all compounds had considerable antimalarial activity against both the strains and further docking studies were performed on both wild type (1J3I.pdb) and quadruple mutant (N51I, C59R, S108 N, I164L, 3QG2.pdb) pf-DHFR-TS to quantify the structural parameter necessary for the activity.

Design, Synthesis, Antibacterial Activity, and Molecular Docking Studies of Novel Hybrid 1,3- Thiazine-1,3,5-Triazine Derivatives as Potential Bacterial Translation Inhibitor

Some novel hybrid 1,3‐thiazine‐1,3,5‐triazine derivatives were synthesized and tested for antibacterial activity. Compounds 8c and 8f were found active against Gram positive and Gram negative microorganisms. Molecular docking studies have been performed on eubacterial ribosomal decoding A site (Escherichia coli 16S rRNA A site) to rationalize the probable mode of action, binding affinity, and orientation of the molecules at the active site of receptor. The structures of all these newly synthesized compounds were confirmed by their elemental analyses and spectral data techniques viz. IR, 1H NMR, 13C NMR, and mass.

Anti-HIV Drug Development: Structural Features and Limitations of Present Day Drugs and Future Challenges in the Successful HIV/AIDS Treatment

Acquired Immune Deficiency Syndrome (AIDS), an immuno-compromized condition, a sequel to untreated human immunodeficiency virus (HIV) infection, inviting several life-threatening diseases, has become one of the most fatal disorders in the recent past because of HIV strain variance due to mutations, passive latency and reservoirs helping in replenishing and reviving the HIV-1 proviral DNA. Scientific efforts have led to the discovery of several effective drugs against HIV and lowered the morbidity and mortality all over the world. However, despite availability of a good number of anti-HIV drugs, the problem, for the foreseeable reasons, stands out as the most chronic disease due to the less tolerability and low accessibility of drugs, life-long expensive treatment, and above all, the emergence of drug resistant viral strains. This review dwells upon HIV infection and its proliferation inside the host system, drug targets, different types of drugs, their structural features and mode of interaction with viral targets and drug regimens. It further focuses on topics of latest interest regarding drug development, fixed dose combinations (FDCs), the limitations of present day drugs with their structural features along with their pharmacodynamics, pharmacokinetics and pharmacogenomics and the challenges in finding a permanent cure for HIV/AIDS.

Phenyl hydrazone bearing pyrazole and pyrimidine scaffolds: design and discovery of a novel class of non-nucleoside reverse transcriptase inhibitors (NNRTIs) against HIV-1 and their antibacterial properties

A novel series of phenyl hydrazone bearing pyrazole and pyrimidine hybrid compounds has been designed using the molinspiration toolkit based on Lipinskis rule of five and developed via sequential reactions starting from the diazotization of different anilines and further active methylation with acetyl acetone, ethyl acetoacetate and ethyl cyanoacetate to generate hydrazono derivatives. The target hybrid compounds were synthesized on cyclisation of the resulting hydrazono derivatives with hydrazine, phenyl hydrazine and urea. These molecules have been subsequently tested for anti-HIV activity using TZM-bl cell lines. The MTT assay was also carried out for the cytotoxicity determination of the active compounds. Further, to exemplify the key structural features of the molecules, a molecular docking analysis of the most active compounds was performed at the NNIBP of the HIV-RT protein. The antibacterial activity of the target compounds was also determined against a panel of four Gram-positive and four Gram-negative human pathogens. All molecules showed a potent anti-HIV activity along with a prominent inhibition of bacterial organisms.

Some Novel Adenosine Mimics: Synthesis and Anticancer Potential against Cervical Cancer caused by Human Papilloma Virus

Two novel adenosine analogs, viz. 9-(1′-β-D-arabinofuranosyl)-6-nitro-1,3-dideazapurine or Ara-NDDP (1) and 9-(5′-deoxy-5′-S-(propionic acid) (1′-β-D-ribofuranosyl) adenine or SAH analog (2), indigenously synthesized, have been found to be potential anticancer agents against cervical cancer caused by human papilloma virus.