Diversity-Oriented Synthesis of Benzo[f][1,4]oxazepine-, 2H-Chromene-, and 1,2-Dihydroquinoline-Fused Polycyclic Nitrogen Heterocycles under Microwave-Assisted Conditions.

An efficient, diversity-oriented synthesis of oxazepino[5,4-b]quinazolin-9-ones, 6H-chromeno[4,3-b]quinolines, and dibenzo[b,h][1,6]naphthyridines was established involving a substrate-based approach under microwave-assisted and conventional heating conditions in high yields (up to 88%). The CuBr2-catalyzed, chemoselective cascade annulation of O-propargylated 2-hydroxybenzaldehydes and 2-aminobenzamides delivered oxazepino[5,4-b]quinazolin-9-ones involving a 6-exo-trig cyclization-air oxidation-1,3-proton shift-7-exo-dig cyclization sequence. This one-pot process showed excellent atom economy (-H2O) and constructed two new heterocyclic rings (six- and seven-membered) and three new C-N bonds in a single synthetic operation. On the other side of diversification, the reaction between O/N-propargylated 2-hydroxy/aminobenzaldehydes and 2-aminobenzyl alcohols delivered 6H-chromeno[4,3-b]quinolines and dibenzo[b,h][1,6]naphthyridines involving sequential imine formation-[4 + 2] hetero-Diels-Alder reaction-aromatization steps. The influence of microwave assistance was superior to conventional heating, where the reactions were clean, rapid, and completed in 15 min, and the conventional heating required a longer reaction time at a relatively elevated temperature.

Microwave-assisted one-pot two-step imine formation-hetero-Diels-Alder-detosylation/aromatization sequence: direct access to dibenzo[b,h][1,6]naphthyridines.

A microwave-assisted, copper-catalyzed, one-pot, two-step reaction is established to access functionalized [1,6]naphthyridines in high yields (up to 96%) starting from 2-(N-propargylamino)benzaldehydes and arylamines. This rapid and operationally simple sequential reaction allowed the construction of two new heterocyclic rings and three new (2 C-C and 1 C-N) bonds in a single synthetic operation. This reaction tolerated various electron-donating and electron-withdrawing substituents well and delivered the desired products in a shorter reaction time under microwave irradiation. This reaction proceeds through a sequential imine formation, intramolecular [4 + 2] hetero-Diels-Alder reaction, and air oxidation, followed by detosylation-aromatization steps.

Trichoderma lixii (IIIM-B4), an endophyte of Bacopa monnieri L. producing peptaibols.

BACKGROUND: Exploration of microbes isolated from north western Himalayas for bioactive natural products. RESULTS: A strain of Trichoderma lixii (IIIM-B4) was isolated from Bacopa monnieri L. The ITS based rDNA gene sequence of strain IIIM-B4 displayed 99% sequence similarity with different Trichoderma harzianum species complex. The highest score was displayed for Hypocrea lixii strain FJ462763 followed by H. nigricans strain NBRC31285, Trichoderma lixii strain CBS 110080, T. afroharzianum strain CBS124620 and Trichoderma guizhouense BPI:GJS 08135 respectively. Position of T. lixii (IIIM-B4) in phylogenetic tree suggested separate identity of the strain. Microbial dynamics of T. lixii (IIIM-B4) was investigated for small peptides. Medium to long chain length peptaibols of 11 residue (Group A), 14 residue (Group B) and 17 residue (Group C) were identified using Matrix Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) mass spectrometer. Optimization is undeniably a desideratum for maximized production of desirable metabolites from microbial strain. Here optimization studies were carried out on T. lixii (IIIM-B4) using different growth media through Intact Cell Mass Spectrometry (ICMS). A multifold increase was obtained in production of 11 residue peptaibols using rose bengal medium. Out of these, one of them named as Tribacopin AV was isolated and sequenced through mass studied. It was found novel as having unique sequence Ac-Gly-Leu-Leu-Leu-Ala-Leu-Pro-Leu-Aib-Val-Gln-OH. It was found to have antifungal activity against Candida albicans (25 µg/mL MIC). CONCLUSION: In this study, we isolated a strain of T. lixii (IIIM-B4) producing medium and long chain peptaibols. One of them named as Tribacopin AV was found novel as having unique sequence Ac-Gly-Leu-Leu-Leu-Ala-Leu-Pro-Leu-Aib-Val-Gln-OH, which had antifungal properties.

Iodine-NH4OAc mediated regioselective synthesis of 2-aroyl-3-arylimidazo[1,2-a]pyridines from 1,3-diaryl-prop-2-en-1-ones.

The present protocol describes an efficient, metal-free regioselective synthesis of 2-aroyl-3-arylimidazo[1,2-a]pyridines from 1,3-diaryl-prop-2-en-1-ones and 2-aminopyridine. The iodine-NH4OAc promoted reaction offers a novel route in the synthesis of 2-aroyl-3-arylimidazo[1,2-a]pyridines. This protocol offers significant flexibility in accessing medicinally important 2-aroyl-3-arylimidazo[1,2-a]pyridines with various substitution patterns.

Divergent synthesis of 4,6-diarylated pyridin-2(1H)-ones from chalcones: novel access to 2,4,6-triaryl pyridines.

A wide range of 4,6-diarylated/heterylated pyridin-2(1H)-one derivatives were synthesized in good to excellent yields from 1,3-diarylated/heterylated-2-propen-1-ones (chalcones) in one pot under metal and base-free conditions. This domino reaction suggests a novel mechanism comprising of Michael addition followed by amination, subsequent intramolecular amidation and finally dehydronitrosation. The usefulness of the designed 4,6-diarylated/heterylated pyridin-2(1H)-one derivatives has further been demonstrated by synthesizing medicinally important 2,4,6-triaryl/heteryl pyridines via Pd-catalyzed cross-coupling reaction.

Quinoxalinone substituted pyrrolizine (4h)-induced dual inhibition of AKT and ERK instigates apoptosis in breast and colorectal cancer by modulating mitochondrial membrane potential.

AKT and ERK 1/2 play a pivotal role in cancer cell survival, proliferation, migration, and angiogenesis. Therefore, AKT and ERK 1/2 are considered crucial targets for cancer intervention. In this study, we envisaged the role of AKT and ERK signaling in apoptosis regulation in presence of compound 4h, a novel synthetic derivative of quinoxalinone substituted spiropyrrolizines exhibiting substantial antiproliferative activity in various cancer cell lines. Structurally 4h is a spiropyrrolizine derivative. Molecular docking analysis revealed that compound 4h shows strong binding affinity with AKT-1 (-9.5 kcal/mol) and ERK2 (-9.0 kcal/mol) via binding at allosteric sites of AKT and active site of ERK2. The implications of 4h binding with these two survival kinases resulted in the obstruction for ATP binding, hence, hampering their phosphorylation dependent activation. We demonstrate that 4h mediated apoptotic induction via disruption in the mitochondrial membrane potential of MCF-7 and HCT-116 cells and 4h-mediated inhibition of survival pathways occurred in a wild type PTEN background and is diminished in PTEN-/- cells. In 4T1 mammary carcinoma model, 4h exhibited pronounced reduction in the tumor size and tumor volume at significantly low doses. Besides, 4h reached the highest plasma concentration of 5.8 µM within a period of 1 h in mice model intraperitoneally. Furthermore, 4h showed acceptable clearance with an adequate elimination half-life and satisfactory pharmacokinetic behaviour, thus proclaiming as a potential lead molecule against breast and colorectal cancer by specifically inhibiting simultaneously AKT and ERK1/2 kinases.

Fluorescence "Turn-Off" and Colorimetric Sensor for Fe2+, Fe3+, and Cu2+ Ions Based on a 2,5,7-Triarylimidazopyridine Scaffold.

Two cyanoimidazopyridine-based sensors (SS1 and SS2) were explored for the colorimetric and fluorometric detection of Fe2+, Fe3+, and Cu2+ ions in the semi-aqueous medium. The "turn-off" fluorescence response of both sensors to these ions was due to the restriction in internal charge transfer. Job's plot and semi-empirical calculations revealed that SS1 and SS2 complexed with Cu2+ ions in a 1:1 ratio and Fe2+/3+ ions in a 2:1 ratio, respectively. The sensors were found to have high binding constant (K a) values and low detection limit values. FMO analysis using the semi-empirical quantum mechanics method revealed the decrease in energy gap after complexation with metal ions. Sensor-coated filter paper strips were prepared and analyzed, where the color changes in the strips could be utilized for the real-time detection of Fe2+, Fe3+, and Cu2+ ions.

An efficient synthesis of 4-phenoxy-quinazoline, 2-phenoxy-quinoxaline, and 2-phenoxy-pyridine derivatives using aryne chemistry.

Herein we report the mild and efficient synthesis of 4-phenoxyquinazoline, 2-phenoxyquinoxaline, and 2-phenoxypyridine derivatives from the starting materials viz. quinazolin-4(3H)-one, quinoxalin-2(1H)-one, and pyridin-2(1H)-one and aryne generated in situ from 2-(trimethylsilyl)phenyl trifluoromethanesulfonate and cesium fluoride. This synthetic methodology gives a new environmentally benign way for the preparation of several unnatural series of 4-phenoxyquinazoline, 2-phenoxyquinoxaline and 2-phenoxypyridine compounds with high yields and broad substrate scope.

Malononitrile-activated synthesis and anti-cholinesterase activity of styrylquinoxalin-2(1H)-ones.

Herein, we report a base-free malononitrile activated condensation of 3-methylquinoxaline-2(1H)-one (3MQ) 1 with aryl aldehydes 3a-3ad for synthesis of styrylquinoxalin-2(1H)-ones (SQs) 4a-4ad with excellent yields. In this reaction, malononitrile activates the aldehyde via Knoevenagel condensation towards reaction with 3MQ 1 and gets liberated during the course of reaction to yield the desired SQs 4a-4ad. The SQs were evaluated for in vitro cholinesterase inhibition and 4n was found to display a mixed type of inhibition of AChE, which was supported by molecular modelling studies. This study has led to the discovery of a new chemotype for cholinesterase inhibition which might be useful in finding a remedy for Alzheimer's disease.

Carbohydrate Modifications of Neoandrographolide for Improved Reactive Oxygen Species-Mediated Apoptosis through Mitochondrial Pathway in Colon Cancer.

Modifications at the carbohydrate moiety of neoandrographolide, isolated from the medicinal plant Andrographis paniculata, result in more potent and less toxic derivatives, namely, 4',6'-benzylidene neoandrographolide (2b) and 4'6'-p-methoxybenzylidene neoandrographolide (2c). These showed improved cytotoxicity against SW-620, PC-3, and A549 cancer cell lines. Nuclear morphology studies were conducted on compound 2b by 4',6-diamidino-2-phenylidole staining and detection of intracellular reactive oxygen species (ROS) accumulation. It showed an increase in the generation of cellular and mitochondrial ROS level. The probable relation of B-cell lymphoma-2 (Bcl-2, an apoptosis inhibitor) to B-cell lymphoma-2-associated X protein (Bax, an apoptosis promoter) ratio with caspase-3 (apoptosis coordination enzyme) in the colon cancer cell line SW-620 was investigated, and it was discovered that upon 2b treatment, the expression of caspase-3 Bax increased remarkably. However, in 2b-treated cells, the expression of Bcl-2 was downregulated as compared to untreated cells.

Isolation of depsipeptides and optimization for enhanced production of valinomycin from the North-Western Himalayan cold desert strain Streptomyces lavendulae.

Exploration of microbial dynamics of Streptomyces lavendulae ACR-DA1, a psychrotrophic isolate from the North-Western Himalayan cold desert, was carried out using matrix-assisted laser desorbtion ionisation-time of flight mass spectrometer. Valinomycin was found as a major produce and cyclic depsipeptide montanastatin as a minor produce. The yield of the valinomycin was found to be 0.3 mg l-1 in submerged growth condition at the batch scale. Miniaturization of optimization experiments was adept to maximize the production using the expeditious and efficient technique of intact cell mass spectrometry. The present study showed that using optimized conditions and growing the culture in synthetic mineral base starch medium at 10 °C enhanced the production to 19.4 mg l-1. Our results demonstrated 64-fold increase in yield from the wild-type S. lavendulae ACR-DA1 strain using a simple and economical downstream process.

Camphor sulphonic acid mediated quantitative 1,3-diol protection of major Labdane diterpenes isolated from Andrographis paniculata.

Phytochemical survey of the methanol extract of the dried aerial parts of Andrographis paniculata led to the isolation of major labdane diterpenes, namely 14-deoxy-11,12-didehydroandrographolide, andrographolide and neoandrographolide. Andrographolide was found to be the major phytoconstituent of the plant which was biologically active. For better physiochemical characteristics and bioefficacy, andrographolide is subjected to semi-synthetic modifications. However, presence of several free hydroxyl groups associated with this molecule make it quite polar and poorly soluble in many organic solvents and hence unsuitable for synthetic modifications. One way of resolving its solubility issue is to protect 1,3-diol quantitatively under mild reaction condition without effecting other functional groups. Reaction conditions were optimised using different solvent systems and catalysts towards this direction. X-ray structure of 3,19-isopropylidene-14-deoxy-11,12-didehydroandrographolide is being reported here for the first time. Isolated compounds and derivatives were confirmed by spectral analysis or X-ray data analysis.

Discovery of Novel and Orally Bioavailable Inhibitors of PI3 Kinase Based on Indazole Substituted Morpholino-Triazines.

A new class of potent PI3Kα inhibitors is identified based on aryl substituted morpholino-triazine scaffold. The identified compounds showed not only a high level of enzymatic and cellular potency in nanomolar range but also high oral bioavailability. The three lead molecules (based on their in vitro potency) when evaluated further for in vitro metabolic stability as well as pharmacokinetic profile led to the identification of 26, as a candidate for further development. The IC50 and EC50 value of 26 is 60 and 500 nM, respectively, for PI3Kα enzyme inhibitory activity and ovarian cancer (A2780) cell line. The identified lead also showed a high level of microsomal stability and minimal inhibition activity for CYP3A4, CYP2C19, and CYP2D6 at 10 µM concentrations. The lead compound 26, demonstrated excellent oral bioavailability with an AUC of 5.2 µM at a dose of 3 mpk in mice and found to be well tolerated in mice when dosed at 30 mpk BID for 5 days.