Studies in the rearrangement reactions involving camphorquinone.

Skeletal rearrangements of camphor are well-known, however, those involving camphorquinone, its sibling, are rare. We have found that the diol derived from allylated camphorquinone undergoes iodine or bromine mediated deep-seated skeletal rearrangement to provide an interesting tricyclic ring system. The iodo group in the rearranged product provided convenient leverage for further functionalization. For example, it was converted into an azide and the azide was subjected to copper(i) mediated Huisgen 1,3-dipolar cycloaddition with acetylenes to obtain a terpene-triazole conjugate.

Crystal structure analysis of ethyl 3-(4-chloro-phen-yl)-1,6-dimethyl-4-methyl-sulfanyl-1H-pyrazolo[3,4-b]pyridine-5-carboxyl-ate.

In the title compound, C18H18ClN3O2S, the dihedral angle between the fused pyrazole and pyridine rings is 3.81 (9)°. The benzene ring forms dihedral angles of 35.08 (10) and 36.26 (9)° with the pyrazole and pyridine rings, respectively. In the crystal, weak C-H⋯O hydrogen bonds connect mol-ecules along [100].

One-Pot Synthesis of Densely Substituted Pyrazolo[3,4-b]-4,7-dihydropyridines.

We have achieved a facile synthesis of a combinatorial library of densely substituted pyrazolo[3,4-b]-4,7-dihydropyridines- the mimics of antigenital wart drug podophyllotoxin-from 5-aminopyrazoles and 4-(methylthio) 4H-chromenes. The C(4) pyrazolyl 4H-chromenes, which also possess structural features of podophyllotoxin, were isolable intermediates in the two-step, one-pot condensation. The condensation took place in a one-pot, multicomponent manner when 3-oxo-3-phenylpropanenitriles, hydrazine (precursors for 5-aminopyrazoles) and 4-(methylthio)-4H-chromenes were heated in refluxing ethanol. The condensation, however, stops at 4H-chromene stage when methyl hydrazine or phenylhydrazine were employed. Our findings offer an opportunity for synthesis of a combinatorial library of podophyllotoxin mimics, thus paving the way for discovery of lead candidates for cancer treatment.

In-silico and in-vitro anti-cancer potential of a curcumin analogue (1E, 6E)-1, 7-di (1H-indol-3-yl) hepta-1, 6-diene-3, 5-dione.

PURPOSE: Previously we showed that BDMC, an analogue of curcumin suppresses growth of human breast and laryngeal cancer cell line by causing apoptosis. Here, we demonstrate the enhanced anti-cancer activity of a heterocyclic ring (indole) incorporated curcumin analogue ((1E, 6E)-1, 7-di (1H-indol-3-yl) hepta-1, 6-diene-3, 5-Dione), ICA in short, in comparison to curcumin. METHOD: ICA was synthesized by a one pot condensation reaction. Anti-cancer potential of ICA was assessed in three human cancer cell lines of different origin (Lung adenocarcinoma (A549), leukemia (K562) and colon cancer (SW480)) by MTT assay. Mode of cell death was determined by acridine orange-ethidium bromide (Ao-Eb) staining. Putative cellular targets of ICA were investigated by molecular docking studies. Cell cycle analysis following curcumin or ICA treatment in SW480 cell line was carried out by flow cytometry. Expression levels of Cyclin D1 and apoptotic markers, such as Caspase 3, 8 and 9 were studied by western blot analysis in SW480 cell line treated with or without ICA and curcumin. RESULTS: The yield of ICA synthesis was found to be 69% with a purity of 98%. ICA demonstrated promising anti-cancer activity compared to curcumin alone, as discerned by MTT assay. ICA was non-toxic to the cell line of normal origin. We further observed that ICA is ∼2 fold more potent than curcumin in inhibiting the growth of SW480 cells. Ao-Eb staining revealed that ICA could induce apoptosis in all the cell lines tested. Molecular docking studies suggest that ICA may possibly exhibit its anticancer effect by inhibiting EGFR in A549, Bcr-Abl in K562 and GSK-3ß kinase in SW480 cell line. Moreover, ICA showed strong binding avidity for Bcl-2 protein in silico, which could result in induction of apoptosis. Cell cycle analysis revealed that both curcumin and ICA induced concomitant cell cycle arrest at G0/G1 and G2/M phase. Western blot shows that ICA could effectively down regulate the expression of cell cycle protein cyclin D1, while promoting the activation of Caspase 3, 8 and 9 when compared to curcumin in human colon cancer cell line SW480. CONCLUSION: The result of this study indicates that ICA could hold promise to be a potential anti-cancer agent. Since ICA has shown encouraging results in terms of its anti-cancer activity compared to curcumin, further research is necessary to fully delineate the underlying molecular mechanism of its anticancer potential.

The quorum sensing molecule N-acyl homoserine lactone produced by Acinetobacter baumannii displays antibacterial and anticancer properties.

Secretory N-acyl homoserine lactones (AHLs) mediate quorum sensing (QS) in bacteria. AHLs are shown to be inhibitory for an unrelated group of bacteria and might mimic host signalling elements, thereby subverting the regulatory events in host cells. This study investigated the AHL produced by Acinetobacter baumannii and analysed its effect on other bacterial species and mammalian cells. Chemically characterized AHL had an m/z value of 325 with a molecular formula C18H31NO4 and showed its inhibitory potential against Staphylococcus aureus. Molecular docking studies identified D-alanine-D-alanine synthetase A, a cell wall synthesizing enzyme of S. aureus having a strong binding affinity towards AHL. Electron microscopy showed the disruption and sloughing off of the S. aureus cell wall when treated with AHL. In vitro experiments revealed that this bacteriostatic AHL showed time-dependent activity and induced apoptosis in cancer cell lines. This compound could be a potential structural backbone for constructing new AHL analogues against S. aureus. The findings emphasize the need to re-evaluate all previously characterized AHLs for any additional new biological functions other than QS.

Copper-mediated arylation with arylboronic acids: Facile and modular synthesis of triarylmethanes.

A facile and modular synthesis of triarylmethanes was achieved in good yield via a two-step sequence in which the final step is the copper(II)-catalyzed arylation of diarylmethanols with arylboronic acids. By using this protocol a variety of symmetrical and unsymmetrical triarylmethanes were synthesized. As an application of the newly developed methodology, we demonstrate a high-yielding synthesis of the triarylmethane intermediate towards an anti-breast-cancer drug candidate.

Synthesis, in vitro and in silico antimalarial activity of 7-chloroquinoline and 4H-chromene conjugates.

A new series of chloroquinoline-4H-chromene conjugates incorporating piperizine or azipane tethers were synthesized and their anti-malarial activity were evaluated against two Plasmodium falciparum strains namely 3D7 chloroquine sensitive (CQS) and K1 chloroquine resistant (CQR). Chloroquine was used as the standard and also reference for comparison. The conjugates exhibit intense UV absorption with λmax located at 342 nm (log ε=4.0), 254 nm (log ε=4.2), 223 nm (log ε=4.4) which can be used to spectrometrically track the molecules even in trace amounts. Among all the synthetic compounds, two molecules namely 6-nitro and N-piperazine groups incorporated 7d and 6-chloro and N-azapane incorporated 15b chloroquinoline-4H-chromene conjugates showed significant anti-malarial activity against two strains (3D7 and K1) of P. falciparum. These values are lesser than the values of standard antimalarial compound. Molecular docking results suggested that these two compounds showing strong binding affinity with P. falciparum lactate dehydrogenase (PfLDH) and also they occupy the co-factor position which indicated that they could be the potent inhibitors for dreadful disease malaria and specifically attack the glycolytic pathway in parasite for energy production.

Di-rhamnolipid is a mosquito pupicidal metabolite from Pseudomonas fluorescens (VCRC B426).

Pseudomonas fluorescens Migula (VCRC B426) produces a secondary metabolite, which was found to be active against pupae of vector mosquitoes namely Culex quinquefasciatus, Anopheles stephensi and Aedes aegypti. The mosquito pupicidal metabolite from P. fluoescens was mass produced and separated by ethyl acetate extraction and purified further by silica gel column chromatography, FPLC, HPLC and TLC. The purified metabolite was characterized by NMR, FT-IR, LC-MS and MALDI-TOF. The FT-IR, (1)H and (13)C NMR results showed that it is a rhamnolipid (di-rhamnolipid). The matrix assisted laser desorption and ionization-time-of-flight spectrum of the sample showed predominant pupicidal component produced by P. fluorescens was the molecule mass of 673.40 Da. Owing to its high toxicity to mosquito pupae, especially Anopheles sp., and Aedes sp., the di-rhamnolipd has potential in the control of the vectors of dengue, chikungunya, yellow fever and malaria. This is the first report of mosquito pupicidal di-rhamnolipid from P. fluorescens.

Copper-catalyzed C(sp3)-OH cleavage with concomitant C-C coupling: synthesis of 3-substituted isoindolinones.

Copper(II) trifluoromethanesulfonate (Cu(OTf)2) efficiently catalyzes the C-C coupling of 3-hydoxyisoindolinones with a variety of aryl-, heteroaryl-, and alkenylboronic acids to furnish C(3) aryl-, heteroaryl-, and alkenyl-substituted isoindolinones. The coupling reactions work smoothly in 1,2-dicholoroethane (DCE) reflux, to effect both inter- and intramolecular versions. This is the first report on C(sp(3))-OH cleavage with concomitant C-C coupling. The photolabile 2-nitrobenzyl protecting group is most appropriate for promotion of the coupling reaction and for deprotection. The tetracyclic ring motif of the alkaloid neuvamine was prepared by applying the newly developed copper-catalyzed C-C coupling.

One-pot pseudo three-component reaction of nitroketene-N,S-acetals and aldehydes for synthesis of highly functionalized hexa-substituted 1,4-dihydropyridines.

We have described the simple, convenient and high yielding one-pot synthesis of a library of highly functionalized hexa-substituted 1,4-dihydropyridines (1,4-DHPs) by 2-aminopyridine catalysed pseudo three-component reaction of nitroketene-N,S-acetals and aldehydes. This domino transformation involves formation of dihydropyridine ring by creation of two C-C bonds and one C-N bond, all of them taking place in a single synthetic operation. As the products precipitate out of the reaction simple filtration is enough to gather the products and thus, there is no need for work-up or column-chromatography. The C6-methylsulfanyl group in the product 1,4-DHPs was substituted with primary and secondary amines to provide 1,4-DHPs with further possibilities in structural diversity. As a demonstration of application of the method we have synthesised an analogue of nitenpyram, a neonicotinoid insecticide.

Photophysical behavior of a new cholesterol attached coumarin derivative and fluorescence spectroscopic studies on its interaction with bile salt systems and lipid bilayer membranes.

A new fluorescent-cholesterol (Cum-Chl) molecule has been synthesized by attaching 3-acetyl-7-(diethylamino)-2H-chromen-2-one (Cum) to cholesterol via cholesterol bound ß-keto ester. The ß-keto ester was synthesized from the corresponding nitrile by applying the Blaise reaction. The molecule forms H-aggregates in solutions. The efficiency of aggregation is high in water. The H-aggregates are non-fluorescent in non-aqueous solvents but fluorescent in water. Aqueous bile salt media suppress the formation of H-aggregates, this effect being more pronounced for sodium deoxycholate (NaDC) which is more hydrophobic. With increasing bile salt concentration, the enhancement of monomeric fluorescence intensity of Cum-Chl generally follows the progressive miceller aggregation of bile salts. Incorporation of Cum-Chl into the dimyristoylphosphatidylcholine (DMPC) lipid bilayer membrane results in a significant enhancement of monomeric fluorescence intensity. The variation of fluorescence intensity is also sensitive to the thermotropic phase transition of the bilayer. It is seen that in such aqueous micro- and nanoscale organized media like bile salts and lipid bilayer membranes the monomer-to-aggregate fluorescence intensity ratio reflects the state of organization of the medium.

(Z)-3-(1-Hy-droxy-3-oxobut-1-en-yl)-6-nitro-2H-chromen-2-one.

In the title compound, C(13)H(9)NO(6), the coumarin system has the benzene ring aligned at 0.61 (18)° with respect to the pyrone ring. An intra-molecular O-H⋯O hydrogen bond stabilizes the mol-ecular conformation and a C-H⋯O contact also occurs. In the crystal, weak C-H⋯O inter-actions link the mol-ecules, forming inversion dimers.

Synthesis and in silico evaluation of 1N-methyl-1S-methyl-2-nitroethylene (NMSM) derivatives against Alzheimer disease: to understand their interacting mechanism with acetylcholinesterase.

Anomalous action of human acetylcholinesterase (hAChE) in Alzheimer's disease (AD) was restrained by various AChE inhibitors, of which the specific and potent lead candidate Donepezil is used for treating the disease AD. Besides the specificity, the observed undesirable side effects caused by Donepezil invoked the quest for new lead molecules with the increased potency and specificity for AChE. The present study elucidates the potency of six 1N-methyl-1S-methyl-2-nitroethylene (NMSM) derivatives to form a specific interaction with the peripheral anionic site and catalytic anionic subsite residues of hAChE. The NMSMs were prepared in good yield from 1,1-di(methylsulfanyl)-2-nitroethylene and primary amine (or) amino acid esters. In silico interaction analysis reveals specific and potent interactions between hAChE and selected ligand molecules. The site-specific interactions formed between these molecules also results in a conformational change in the orientation of active site residues of hAChE, which prevents them from being accessed by beta-amyloid protein (Aß), which is a causative agent for amyloid plaque formation and acetylcholine (ACh). In silico interaction analysis between the ligand-bounded hAChE with Aß and ACh confirms this observation. The variation in the conformation of hAChE associated with the decreased ability of Aß and ACh to access the respective functional residues of hAChE induced by the novel NMSMs favors their selection for in vivo analysis to present themselves as new members of hAChE inhibitors.

6,8-Dichloro-N-methyl-3-nitro-4-nitro-methyl-4H-chromen-2-amine.

In the title compound, C(11)H(9)Cl(2)N(3)O(5), the dihydro-pyran ring adopts a near-half-chair conformation. The benzene ring makes a torsion angle of 5.02 (5)° with the dihydro-pyran ring. Adjacent mol-ecules are inter-linked through inter-molecular C-H⋯O, N-H⋯O and C-Cl⋯π [3.4743 (9) Å] inter-actions. The inter-molecular N-H⋯O hydrogen bond generates an R(2) (2)(12) motif, which is observed to contribute to the crystal packing stability. Moreover, the mol-ecular structure displays an S(6) motif formed by intra-molecular N-H⋯O hydrogen bonding.

6-Meth-oxy-N-methyl-3-nitro-4-nitro-methyl-4H-chromen-2-amine.

In the title compound, C(12)H(13)N(3)O(6), the dihydro-pyran ring adopts a near screw-boat conformation. The dihedral angle between the mean planes of the benzene and dihydro-pyran rings is 6.35 (5)°. An intra-molecular N-H⋯O hydrogen bond generates an S(6) motif, which stabilizes the mol-ecular conformation. In the crystal, weak inter-molecular C-H⋯O, N-H⋯O and C-H⋯π hydrogen bonds contribute to the stabilization of the packing.

4-[4-(Diethyl-amino)-phen-yl]-N-methyl-3-nitro-4H-chromen-2-amine.

In the title compound, C(20)H(23)N(3)O(3), the dihydro-pyran ring adopts half-chair conformation. The chromene system makes a dihedral angle of 87.35 (5)° with the adjacent benzene ring. An intra-molecular N-H⋯O hydrogen bond generates an S(6) motif, which stabilizes the mol-ecular conformation. In the crystal, weak inter-molecular C-H⋯O hydrogen bonds contribute to the stabilization of the packing.

Nitroketene dithioacetal chemistry: Synthesis of 2-alkylthio-3-nitrothiophenes from nitroketene dithioacetate and chloromethyl ketones.

An effective synthesis of highly functionalized 3-nitrothiophenes was achieved from the reaction of simple, inexpensive, and readily available dipotassium 2-nitro-1,1-ethylyenedithiolate with alpha-chloromethyl ketones in toluene catalyzed by tetrabutylammonium bromide (TBAB). Thiophene formation is highly sensitive and selective for chlorine, present as a leaving group in alpha-chloromethyl ketones.

Chair to boat interconversion and face to face interactions in isomeric aryl-substituted perhydrocyclopentaquinolizines.

The structure and the conformation of the two isomeric 3,5-di(4-methoxyphenyl)perhydrocyclopenta[ij]quinolizines 1 and 2 have been determined by a combination of NOE experiments, analysis of vicinal J coupling constants, and DFT computations. The two aryl rings were found to exhibit a face to face disposition, and variable-temperature NMR spectra allowed the determination of the corresponding rotation barriers, as well as chair to boat and nitrogen inversion processes of the quinolizine rings. The structure and the conformation of the two corresponding ammonium salts 1-H+ and 2-H+ were also obtained in solution by the same techniques: in addition, their solid-state structures were determined by X-ray diffraction.

Aroylketene dithioacetal chemistry: facile synthesis of 4-aroyl-3-methylsulfanyl-2-tosylpyrroles from aroylketene dithioacetals and TosMIC.

The cycloaddition of the von Leusen's reagent (p-tolylsulfonyl)methyl isocyanide (TosMIC) to alpha-aroylketene dithioacetals (AKDTAs) in the presence of sodium hydride in THF at rt resulted in a facile synthesis of the 4-aroyl-3-methylsulfanyl-2-tosylpyrroles 3 in good yield along with a minor amount of 4-[(4-methylphenyl)sulfonyl]-1-[(methylsulfanyl)methyl]-1H-imidazole 4. This study lead to the synthesis of 2,3,4-trisubstiuted pyrroles having 1-naphthoyl/2-naphthoyl/ferrocenoyl/pyrenoyl scaffolds on C-4 of the pyrrole ring. In this transformation, the AKDTAs behave as a 3-(methylsulfanyl)-1-aryl-2-propyn-1-one (ArCOC identical withCSMe) equivalent. Competition experiments clearly showed that the cycloaddition of TosMIC to "push-pull" alkenes like AKDTAs is slower compared to general alpha,beta-unsaturated carbonyl compounds.

Condensation of alpha-aroylketene dithioacetals and 2-hydroxyarylaldehydes results in facile synthesis of a combinatorial library of 3-aroylcoumarins.

A facile, convenient, efficient, and high yielding synthesis of a combinatorial library of 3-aroylcoumarins has been developed by the condensation of easily available alpha-aroylketene dithioacetals (AKDTAs) and 2-hydroxybenzaldehydes (salicylaldehydes)/2-hydroxy-1-naphthaldehyde in the presence of catalytic amount of piperidine in THF reflux. The condensation of ferrocene derived alpha-aroylketene dithioacetal and 2-hydroxybenzaldehyde furnished coumarin installed on a ferrocene platform.