Bathini Nagendra Babu

MoO2Cl2 catalyzed efficient synthesis of functionalized 3,4-dihydropyrimidin-2(1H)-ones/thiones and polyhydroquinolines: recyclability, fluorescence and biological studies

A simple, facile and efficient synthesis of functionalized dihydropyrimidinones and polyhydroquinolines using molybdenum(VI) dichloride dioxide (MoO2Cl2) has been developed. The present protocol demonstrates the exceptional tolerance towards acid labile protecting groups such as tert-butyl dimethyl silyl (TBDMS) and tert-butyl diphenyl silyl (TBDPS). This is the first report of exploring Lewis acid properties of MoO2Cl2 in the diversity oriented synthesis of Biginelli and Hantzsch reactions. Biologically important and highly structured conjugates of dihydropyrimidinone and polyhydroquinoline derivatives containing coumarin, pyrazole, indole and triazole moieties were synthesized in good to excellent yields. Compound 4o exhibited blue fluorescence at a maximum UV absorbance λmax of 326 nm. In the preliminary MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, compound 4n displayed remarkable cytotoxic activity against A549 and PC3 cell lines while compound 7q was found to be cytotoxic against HGC-27 and PC3 cancer cell lines.

Synthesis and biological evaluation of novel Δ2-isoxazoline fused cyclopentane derivatives as potential antimicrobial and anticancer agents

As a part of our endeavour toward the synthesis of new heterocyclic bioactive agents, three series of Δ2-isoxazoline fused cyclopentane derivatives (27 compounds) were synthesized and characterized by IR, 1H NMR, 13C NMR and MS analysis. The newly synthesized target compounds were evaluated for their preliminary in vitroantimicrobial and anticancer activities. The results indicated that compounds 4b, 4h, 4i, 5d and 5g displayed remarkable anti-microbial activity with respect to their standard drugsAmpicillin, Gentamycin and Amphotericin B. In preliminary MTT cytotoxicity studies, compound 4i was found to be equipotent to the standard drugEtoposide against MCF-7. The influence of the most active cytotoxic compound 4i on the cell cycle distribution was evaluated in the MCF-7 cell line, which displayed a cell cycle arrest at the S phase. Moreover, acridine orange/ethidium bromide staining, annexin V binding assay and mitochondrial membrane potential revealed that compound 4i can induce cell apoptosis in MCF-7 cells. Compounds 4b and 4h are potential leads as antimicrobials owing to no significant cell toxicity observed in the present study. Docking studies revealed that compound 4i binds to Phe1145, Glh698, Met696, Cys1191, Met1169 and Ile1167 on DNA methyltransferase (DNMT1) protein and inhibition of DNMT1 could be the possible mechanism of action for these compounds.

Synthesis and biological evaluation of oxindole linked indolyl-pyrimidine derivatives as potential cytotoxic agents.

In our endeavor towards the development of effective cytotoxic agents, a series of oxindole linked indolyl-pyrimidine derivatives were synthesized and characterized by IR, (1)H NMR, (13)C NMR and Mass spectral analysis. All the newly synthesized target compounds were assessed against PA-1 (ovarian), U-87MG (glioblastoma), LnCaP (prostate), and MCF-7 (Breast) cancer cell lines for their cytotoxic potential, with majority of them showing inhibitory activity at low micro-molar concentrations. Significantly, compound 8e was found to be most potent amongst all the tested compounds with an IC50 value of (2.43±0.29μM) on PA-1 cells. The influence of the most active cytotoxic compound 8e on the cell cycle distribution was assessed on the PA-1 cell line, exhibiting a cell cycle arrest at the G2/M phase. Moreover, acridine orange/ethidium bromide staining and annexin V binding assay confirmed that compound 8e can induce cell apoptosis in PA-1 cells. These preliminary results persuade further investigation on the synthesized compounds aiming to the development of potential cytotoxic agents.

Investigation of triazole-linked indole and oxindole glycoconjugates as potential anticancer agents: novel Akt/PKB signaling pathway inhibitors

In continuation of our venture towards the synthesis of novel bioactive agents, two sets of triazole-linked glycoconjugates were synthesized from indole/oxindole (29 compounds) and were further characterized by IR (infrared spectroscopy), 1H NMR (nuclear magnetic resonance), 13C NMR and mass spectral analysis. The newly synthesized target compounds were evaluated for their preliminary in vitro anticancer activity against DU145 (prostate cancer), HeLa (cervical cancer), A549 (lung cancer) and MCF-7 (breast cancer) cell lines. In the sulforhodamine B (SRB) assay, the results indicated that compounds 5f (indole derivative) and E-9b (oxindole derivative) displayed remarkable cytotoxic activity against DU145 cells. Moreover, the colony formation assay (soft agar assay) revealed that compounds 5f and E-9b can inhibit the growth and proliferation of DU145 cells. The impact of the most active cytotoxic compounds 5f and E-9b on the cell cycle distribution was assessed in DU145 cells, which displayed a cell cycle arrest at the sub-G1 phase. Next, compounds 5f and E-9b were tested for caspase activation in DU145 cells, and the results specified that these compounds have the capability to induce apoptosis in cells through an intrinsic pathway leading to subsequent cell death. Further studies also confirmed that compounds 5f and E-9b act against the protein kinase B (Akt/PKB) pathway to inhibit the proliferation of cancer cells. Thus, compounds 5f and E-9b could be novel potential anticancer leads as the normal cell line NIH/3T3 (fibroblast) studies showed no significant cytotoxicity.

Synthesis and α-Glucosidase Inhibition Activity of Dihydroxy Pyrrolidines

A new series of Deacetylsarmentamide A and B derivatives, amides and sulfonamides of 3,4-dihydroxypyrrolidines as α-glucosidase inhibitors were designed and synthesized. The biological screening test against α-glucosidase showed that some of these compounds have the positive inhibitory activity against α-glucosidase. Saturated aliphatic amides were more potent than the olefinic amides. Among all the compounds, 5o/6o having polar -NH2 group, 10f/11f having polar -OH group on phenyl ring displayed 3-4-fold more potent than the standard drugs. Acarbose, Voglibose and Miglitol were used as standard references. The promising compounds 6i, 5o, 6o, 10a, 11a, 10f and 11f have been identified. Molecular docking simulations were done for compounds to identify important binding modes responsible for inhibition activity of α-glucosidase.

Glycogen synthase kinase-3 and its inhibitors: Potential target for various therapeutic conditions

Glycogen Synthase Kinase-3 (GSK-3) is a serine/threonine kinase which is ubiquitously expressed and is regarded as a regulator for various cellular events and signalling pathways. It exists in two isoforms, GSK-3α and GSK-3β and can phosphorylate a wide range of substrates. Aberrancy in the GSK-3 activity can lead to various diseases like Alzheimers, diabetes, cancer, neurodegeneration etc., rendering it an attractive target to develop potent and specific inhibitors. The present review focuses on the recent developments in the area of GSK-3 inhibitors and also enlightens its therapeutic applicability in various disease conditions.

Design and synthesis of 1,2,3-triazole–etodolac hybrids as potent anticancer molecules

A series of novel 1,2,3-triazole–etodolac hybrids (6a–l) were designed and synthesized as potent anti-cancer molecules. The synthesis strongly relied on Huisgens 1,3-dipolar cycloaddition between etodolac azide 3 and substituted terminal alkynes 5a–l. The use of CH2Cl2 as a co-solvent with H2O increased the reaction rate and provided the corresponding 1,2,3-triazole–etodolac hybrids (6a–l) in excellent yields compared to other organic co-solvent systems. All the compounds were screened for their in vitro anticancer activity against human A549 cell lines and compounds 6e, 6f, 6h, 6j, and 6l were found to be the best anti-cancer molecules as compared to the marketed drug doxorubicin.

Aldehyde-Promoted One-Pot Regiospecific Synthesis of Acrylamides Using an in Situ Generated Molybdenum Tetracarbonyl Amine [Mo(CO)4(amine)2] Complex

A novel complex system generated in situ from Mo(CO)6 and an amine is described for the regiospecific aminocarbonylation of various terminal alkynes. The Mo(CO)6-amine system played a dual role as complexing agent and as CO donor, thus making this process palladium-free.

Synthesis and biological evaluation of strained unusual amino acid containing tetrapeptides as potential antidepressant agents.

Strained unusual amino acid derived tetrapeptides were synthesized as mimics of GLYX-13, a clinical candidate for neuroprotective and anti-depressant properties, were studied. The synthesized compounds were screened for neurite growth and anti-depressant properties in vitro and in vivo respectively comparing with the parent GLYX-13 compound. Neurite growth property was assessed by neurite length and anti-depressant property by percentage of immobility in forced swim test, a behavioural assay. Mechanistic insights about protein-ligand interactions were obtained using molecular docking study. Based on the in vitro and in vivo screening data and molecular docking study, a new analogue of GLYX-13, Compound 11a has been found to be as good as the parent compound in all respects.

Telomerase Inhibition and Human Telomeric G-Quadruplex DNA Stabilization by a β-Carboline–Benzimidazole Derivative at Low Concentrations

Guanine rich regions in DNA, which can form highly stable secondary structures, namely, G-quadruplex or G4 DNA structures, affect DNA replication and transcription. Molecules that stabilize G4 DNA have become important in recent years. In this study, G4 DNA stabilization, inhibition of telomerase, and anticancer activity of synthetic β-carboline-benzimidazole derivatives (5a, 5d, 5h, and 5r) were studied. Among them, derivatives containing a 4-methoxyphenyl ring at C1 and a 6-methoxy-substituted benzimidazole at C3 (5a) were found to stabilize telomeric G-quadruplex DNA efficiently. The stoichiometry and interaction of a synthetic, β-carboline-benzimidazole derivative, namely, 3-(6-methoxy-1H-benzo[d]imidazol-2-yl)-1-(4-methoxyphenyl)-9H-pyrido[3,4-b]indole (5a), with human intermolecular G-quadruplex DNA at low concentrations were examined using electrospray ionization mass spectrometry. Spectroscopy techniques indicate that 5a may intercalate between the two stacks of G-quadruplex DNA. This model is supported by docking studies. When cancer cells are treated with 5a, the cell cycle arrest occurs at the sub-G1 phase. In addition, an apoptosis assay and fluorescence microscopy studies using cancer cells indicate that 5a can induce apoptosis. Results of biochemical assays such as the polymerase chain reaction stop assay and telomerase activity assay indicate that 5a has the potential to stabilize G-quadruplex DNA, and thereby, it may interfere with in vitro DNA synthesis and decrease telomerase activity. The results of this study reveal that the β-carboline-benzimidazole derivative (5a) is efficient in G-quadruplex DNA stabilization over double-stranded DNA, inhibits telomerase activity, and induces apoptosis in cancer cells.