A facile solvent-free three-component domino synthesis of novel 2,4-diaryl-5,6-dihydrobenzo[j][1,7]phenanthrolines.

A simple, efficient and green procedure for the synthesis of novel 2,4-diaryl-5,6-dihydrobenzo[j][1,7]phenanthrolines has been developed via a Krohnke-type one-pot three-component reaction of 2-[arylmethylidene]-3,4-dihydro-1(2H)-acridinones and (2-aryl-2-oxoethyl)pyridinium bromides in the presence of excess ammonium acetate in good yields under solvent-free conditions. Good functional group tolerance, high substrate scope and no column purification are the practical advantages of this methodology.

Synthesis of benzosuberone-tethered spirooxindoles: 1-3-dipolar cycloaddition of azomethine ylides and arylidene benzosuberones.

Expedient synthesis of benzosuberone-tethered spirooxindoles was accomplished by a three-component 1,3-dipolar cycloaddition reaction between azomethine ylide (generated in situ) and arylidene benzosuberone. This protocol offers good yield and wide functional group tolerance under mild reaction condition with high regio- and stereoselectivities.

One-pot microwave assisted stereoselective synthesis of novel dihydro-2'H-spiro[indene-2,1'-pyrrolo-[3,4-c]pyrrole]-tetraones and evaluation of their antimycobacterial activity and inhibition of AChE.

An efficient one-pot microwave assisted stereoselective synthesis of novel dihydro-2'H-spiro[indene-2,1'-pyrrolo[3,4-c]pyrrole]-tetraone derivatives through three-component 1,3-dipolar cycloaddition of azomethine ylides generated in situ from ninhydrin and sarcosine with a series of 1-aryl-1H-pyrrole-2,5-diones is described. The synthesised compounds were screened for their antimycobacterial and AChE inhibition activities. Compound 4b (IC50 1.30µM) has been found to display twelve fold antimycobacterial activity compared to cycloserine and it is thirty seven times more active than pyrimethamine. Compound 4h displays maximum AchE inhibitory activity with IC50 value of 0.78±0.01µmol/L.

A facile stereoselective synthesis of dispiro-indeno pyrrolidine/pyrrolothiazole-thiochroman hybrids and evaluation of their antimycobacterial, anticancer and AchE inhibitory activities.

A facile stereoselective synthesis of novel dispiro indeno pyrrolidine/pyrrolothiazole-thiochroman hybrids has been achieved by 1,3-dipolar cycloaddition of azomethine ylides, generated in situ from ninhydrin and sarcosine/thiaproline, on a series of 3-benzylidenethiochroman-4-ones. The synthesised compounds were screened for their antimycobacterial, anticancer and AchE inhibition activities. Compound 4l (IC50 1.07µM) has been found to exhibit the most potent antimycobacterial activity compared to cycloserine (12 times), pyrimethamine (37 times) and ethambutol (IC50 <1.56µM) and 6l (IC50=2.87µM) is more active than both cycloserine (4 times) and pyrimethamine (12 times). Three compounds, 4a, 6b and 6i, display good anticancer activity against CCRF-CEM cell lines. Compounds 6g and 4g display maximum AchE inhibitory activity with IC50 values of 1.10 and 1.16µmol/L respectively.

One-Pot Access to a Library of Dispiro Oxindole-pyrrolidine/pyrrolothiazole-thiochromane Hybrids via Three-Component 1,3-Dipolar Cycloaddition Reactions.

A library of novel dispiro compounds containing oxindole pyrrolidine/oxindolopyrrolothiazole-thiochroman-4-one hybrid frameworks has been synthesized in a fully regio- and stereoselective fashion by the three-component 1,3-dipolar cycloaddition of azomethine ylides generated in situ from the condensation of isatins and secondary amino acids (sarcosine/l-thioproline) with 3-arylidenethiochroman-4-ones. This experimentally simple protocol provides good yields of structurally complex, biologically relevant heterocycles in a single operation.

An efficient synthesis of N-substituted 3-nitrothiophen-2-amines.

A novel protocol for the synthesis of 3-nitro-N-aryl/alkylthiophen-2-amines in good yields from the reaction of α-nitroketene N,S-aryl/alkylaminoacetals and 1,4-dithiane-2,5-diol in the presence of K2CO3 in refluxing ethanol is described. This transformation generates two C-C bonds in a single operation and presumably proceeds through a reaction sequence comprising 2-mercaptoacetaldehyde generation, nucleophilic carbonyl addition, annelation and elimination steps.

Crystal structures of two 2,9-di-thia-13-aza-dispiro-[4.1.4(7).3(5)]tetra-decan-6-ones.

In the title compounds 4,11-dihy-droxy-13-methyl-1,8-di-p-tolyl-2,9-di-thia-13- aza-dispiro-[4.1.4(7).3(5)]tetra-decan-6-one, C26H31NO3S2, (I), and 13-benzyl-4,11-dihy-droxy-1,8-bis-(4-methyl-phen-yl)-2,9-di-thia-13-aza-dispiro-[4.1.4(7).3(5)]tetradecan-6-one, C32H35NO3S2, (II), the piperidine rings adopt distorted chair conformations. The thio-phene rings in (I) have envelope conformations, with the spiro C atoms as the flaps. In (II), one thio-phene ring (D) has an envelope conformation, with the hy-droxy-substituted C atom as the flap, while the other thio-phene ring (E) has a twisted conformation on the C-C bond involving the spiro C atom and the toluyl-substituted C atom. In (I), the mean plane of the piperidine ring makes dihedral angles of 75.16 (9) and 73.33 (8)° with the mean planes of the thio-phene rings (D and E), respectively. In (II), the corresponding dihedral angles are 70.95 (11) and 77.43 (12)°. In both compounds, there is an intra-molecular O-H⋯O hydrogen bond forming an S(6) ring motif. In the crystal of (I), mol-ecules are linked via O-H⋯N and C-H⋯O hydrogen bonds, forming chains along [010]. There are also π-π inter-actions present involving inversion-related benzene rings, linking the chains to form slabs parallel to (100). In the crystal of (II), mol-ecules are linked via O-H⋯O hydrogen bonds, forming inversion dimers with an R 4 (4)(8) ring motif. The dimers are linked by C-H⋯π inter-actions, forming slabs parallel to (001).

Crystal structure of 4-(1H-indol-3-yl)-2-(4-meth-oxy-phen-yl)-6-phenyl-pyridine-3-carbo-nitrile.

In the title compound, C27H19N3O, the dihedral angles between the plane of the pyridine ring and those of the indole (r.m.s. deviation = 0.018 Å), phenyl and meth-oxy-benzene substituents are 33.60 (6), 25.28 (7) and 49.31 (7)°, respectively. The N atom of the carbo-nitrile group is significantly displaced [0.288 (2) Å] from the plane of the pyridine ring, perhaps due to steric crowding. In the crystal, inversion dimers linked by pairs of N-H⋯Nn (n = nitrile) hydrogen bonds generate R 2 (2)(16) loops. Aromatic π-π stacking [centroid-centroid separation = 3.6906 (7) Å] and very weak C-H⋯π inter-actions are also observed".

Axial chirality of 4-arylpyrazolo[3,4-b]pyridines. Conformational analysis and absolute configuration.

The stereodynamic behavior of a series of pyrazolo[3,4-b]pyridines was studied. The restricted rotations of the aryl substituent in position 4 of the heteroaromatic ring and of the benzoyl group in position 5 generated conformational enantiomers or conformational diastereoisomers depending on the local symmetry of the aryl substituent, with very high rotational barriers despite the absence of ortho-substituents. The energy barriers for the rotation of the 5-benzoyl group and the 4-aromatic ring were measured by dynamic NMR and rationalized by DFT calculations. When the aryl substituent at position 4 was 1-naphthyl, the resulting atropisomeric pair was resolved by means of enantioselective HPLC and the absolute configuration was determined by TD-DFT simulations of electronic circular dichroism spectra.

Crystal structure of 2-(2-bromo-phen-yl)-4-(1H-indol-3-yl)-6-(thio-phen-2-yl)pyridine-3-carbo-nitrile.

In the title compound, C24H14BrN3S, the dihedral angles between the planes of the pyridine ring and the pendant thio-phene ring, the indole ring system (r.m.s. deviation = 0.022 Å) and the bromo-benzene ring are 9.37 (17), 21.90 (12) and 69.01 (15)°, respectively. The approximate coplanarity of the central ring and the indole ring system is supported by two intra-molecular C-H⋯N inter-actions. In the crystal, inversion dimers linked by pairs of N-H⋯N hydrogen bonds generate R 2 (2)(16) loops and the dimers are linked by C-H⋯π and aromatic π-π stacking [shortest centroid-centroid separation = 3.729 (3) Å] into a three-dimensional network.

Crystal structure of 2-(4-chloro-phen-yl)-4-(1H-indol-3-yl)-6-phenyl-pyridine-3-carbo-nitrile.

In the title compound, C26H16ClN3, the dihedral angles between the central pyridine ring and the pendant phenyl, chloro-benzene and indole rings are 18.52 (12), 48.97 (11) and 21.20 (10)°, respectively. An intra-molecular C-H⋯Nc (c = cyanide) hydrogen bond occurs. In the crystal, inversion dimers linked by pairs of N-H⋯Nc hydrogen bonds generate R 2 (2)(16) loops.

Sequential synthesis of amino-1,4-naphthoquinone-appended triazoles and triazole-chromene hybrids and their antimycobacterial evaluation.

A general method for the synthesis of a library of hitherto unreported amino-1,4-naphthoquinone-appended triazoles was accomplished via a sequential three-component reaction of substituted N-propargylaminonaphthoquinones with variously substituted alkyl bromides/2-bromonaphthalene-1,4-dione and sodium azide in the presence of Et3N/CuI in water. Aminonaphthoquinone-appended iminochromene-triazole hybrid heterocycles were also synthesized from the amino-1,4-naphthoquinone-appended-1,2,3-triazolylacetonitriles. All the triazole hybrids were screened for their in vitro activity against Mycobacterium tuberculosis H37Rv (MTB). Among the triazoles, 2-(((1-benzyl-1H-1,2,3-triazol-4-yl)methyl)(4-(trifluoromethyl)phenyl)amino)naphthalene-1,4-dione (7d) emerged as the most active one with IC50 = 1.87 µM, being more potent than the anti-TB drugs, cycloserine (6 times), pyrimethamine (20 times) and equipotent as the drug ethambutol (IC50 < 1.56 µM).

A heavy metal- and oxidant-free, one-pot synthesis of pyridines and fused pyridines based on a Lewis acid-catalyzed multicomponent reaction.

The InCl3-catalyzed sequential multicomponent reaction between 2-furfurylamine, ß-dicarbonyl compounds and α,ß-unsaturated aldehydes in ethanol, followed by microwave irradiation in solvent-free conditions, afforded good to excellent yields of highly substituted pyridines, with loss of a 2-furylmethyl side chain. The method was also adapted to the synthesis of quinolones, isoquinolines, phenanthridines and more complex fused pyridine systems.

A catalyst-free multicomponent domino sequence for the diastereoselective synthesis of (E)-3-[2-arylcarbonyl-3-(arylamino)allyl]chromen-4-ones.

The three-component domino reactions of (E)-3-(dimethylamino)-1-arylprop-2-en-1-ones, 3-formylchromone and anilines under catalyst-free conditions afforded a library of novel (E)-3-(2-arylcarbonyl-3-(arylamino)allyl)-4H-chromen-4-ones in good to excellent yields and in a diastereoselective transformation. This transformation generates one C-C and one C-N bond and presumably proceeds via a reaction sequence comprising a Michael-type addition-elimination reaction, a nucleophilic attack of an enamine to a carbonyl reminiscent of one of the steps of the Bayllis-Hilman condensation, and a final deoxygenation. The deoxygenation is assumed to be induced by carbon monoxide resulting from the thermal decomposition of the dimethylformamide solvent.

A facile chemo-, regio- and stereoselective synthesis and cholinesterase inhibitory activity of spirooxindole-pyrrolizine-piperidine hybrids.

A series of novel hybrid spiro heterocycles comprising pyrrolizine, spiroxindole and piperidine moieties was synthesized chemo-, regio- and stereoselectively in good yields from 1,3-dipolar cycloaddition reaction of a series of 1-acryloyl-3,5-bisarylmethylidenepiperidin-4-ones with azomethine ylides generated in situ from 5-choloroisatin and l-proline in methanol. These cycloadducts displayed significant cholinesterase inhibitory activity. Among the compounds screened, 8g and 8e, showed maximum inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinestrase (BChE) with IC50 values of 3.33 and 3.13µM, respectively.

Synthesis and discovery of novel piperidone-grafted mono- and bis-spirooxindole-hexahydropyrrolizines as potent cholinesterase inhibitors.

Three-component reaction of a series of 1-acryloyl-3,5-bisbenzylidenepiperidin-4-ones with isatin and L-proline in 1:1:1 and 1:2:2 molar ratios in methanol afforded, respectively the piperidone-grafted novel mono- and bisspiro heterocyclic hybrids comprising functionalized piperidine, pyrrolizine and oxindole ring systems in good yields. The in vitro evaluation of cholinesterase enzymes inhibitory activity of these cycloadducts disclosed that monospiripyrrolizines (8a-k), are more active with IC50 ranging from 3.36 to 20.07 µM than either the dipolarophiles (5a-k) or bisspiropyrrolizines (9a-k). The compounds, 8i and 8e with IC50 values of 3.36 and 3.50 µM, respectively showed the maximum inhibition of acethylcholinesterase (AChE) and butrylylcholinestrase (BuChE). Molecular modeling simulation, disclosed the binding interactions of the most active compounds to the active site residues of their respective enzymes. The docking results were in accordance with the IC50 values obtained from in vitro cholinesterase assay.

Synthesis of novel 16-spiro steroids: spiro-7'-(aryl)tetrahydro-1H-pyrrolo[1,2-c][1,3]thiazolo-trans-androsterone hybrid heterocycles.

The 1,3-dipolar cycloaddition of azomethine ylide derived in situ from the reaction of acenaphthylene-1,2-dione and 1,3-thiazolane-4-carboxylic acid to various exocyclic dipolarophiles synthesized from trans-androsterone and trans-dehydroandrosterone afforded a library of novel spiro[5'.2″]acenaphthylene-1″-one-spiro[16.6']-(7'-aryl)-tetrahydro-1H-pyrrolo [1,2-c][1,3]thiazolo-trans-androsterone/dehydroandrosterone hybrid heterocycles respectively. These reactions proceeded stereo-specifically affording a single isomer of the 16-spiro steroids in excellent yields.

Theoretical investigation of quinone metabolites of dopamine interaction with DNA--insights into toxicological effects.

Dopamine (3,4-dihydroxyphenylethylamine, DA), an important neurotransmitter, exists in the cell bodies of the dopaminergic neurons of the substantia nigra. Oxidation of DA to its quinone and subsequent reaction with Adenine and Guanine in DNA result in the formation of depurinating adducts, thus causing DNA damage. In this article, we investigate the interaction of quinone metabolites of dopamine (DMQ) with models representing the structure of DNA using dispersion corrected density functional theory with an aim to evaluate the associated structural changes in DNA upon their interaction. Various binding sites for the DA metabolite on these DNA models have been considered and our computations on the activation barriers allowed us to identify preferential bonding sites for these metabolites analogous to experiments. Analysis of the geometry of these adducts in comparison to free base pairs reveals that the attack of DMQ causes remarkable changes in the structural properties. With our calculations, we propose that these structural alterations induce mutations by favoring the formation of depurinating adducts leading to mutagenic effects such as base mispairing, explaining the toxicological (carcinogenic and neurotoxic) behavior of DMQ.

A facile four-component sequential protocol in the expedient synthesis of novel 2-aryl-5-methyl-2,3-dihydro-1H-3-pyrazolones in water and their antitubercular evaluation.

A series of 2-aryl-5-methyl-2,3-dihydro-1H-3-pyrazolones has been synthesized by one-pot, four-component sequential reactions of phenylhydrazine, methyl acetoacetate, aromatic aldehydes and ß-naphthol in the presence of p-toluenesulphonic acid in water in good yields. These 2-aryl-5-methyl-2,3-dihydro-1H-3-pyrazolones were screened for in-vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (MTB) using agar dilution method. Among the 15 compounds screened, 4-[(2,4-dichlorophenyl)(2-hydroxy-1-naphthyl)methyl]-2-(4-fluorophenyl)-5-methyl-2,3-dihydro-1H-3-pyrazolone displays the maximum potency with a minimum inhibitory concentration (MIC) of 1.6 µM against MTB, being 2.94 and 4.75 times more active than ciprofloxacin and ethambutol respectively.

Synthesis and crystal structures of 5'-phenylspiro[indoline-3, 2'-pyrrolidin]-2-one derivatives.

BACKGROUND: The spiro- indole-pyrrolidine ring system is a frequently encountered structural motif in many biologically important and pharmacologically relevant alkaloids. The derivatives of spirooxindole ring systems are used as antimicrobial, antitumour agents and as inhibitors of the human NKI receptor besides being found in a number of alkaloids like horsifiline, spirotryprostatin and (+) elacomine. The recently discovered small-molecule MDM2 inhibitor MI-219 and its analogues are in advanced preclinical development as cancer therapeutics. RESULTS: In the crystal structures of the two organic compounds, 4'-Nitro-3',5'-diphenylspiro[indoline-3,2'-pyrrolidin]-2-one and 3'-(4-Methoxyphenyl)- 4'-nitro -5'-phenylspiro[indoline-3,2'-pyrrolidin]-2-one, N-H···O hydrogen bonds make the R22 (8) ring motif. Further, the structures are stabilized by intermolecular hydrogen bonds. CONCLUSION: The crystal structures of 4'-Nitro-3',5'-diphenylspiro[indoline-3,2'-pyrrolidin]-2-one and 3'-(4-Methoxyphenyl)- 4'-nitro -5'-phenylspiro[indoline-3,2'-pyrrolidin]-2-one have been investigated in detail. In both the compounds, the R22(8) motif is present. Due to the substitution of methoxyphenyl instead of phenyl ring, the entire configuration is inverted with respect to the 2-oxyindole ring.