Nagaraja Naik

Synthesis of benzofuran based 1,3,5-substituted pyrazole derivatives: As a new class of potent antioxidants and antimicrobials-A novel accost to amend biocompatibility

In search for a new antioxidant and antimicrobial agent with improved potency, we synthesized a series of benzofuran based 1,3,5-substituted pyrazole analogues (5a-l) in five step reaction. Initially, o-alkyl derivative of salicyaldehyde readily furnish corresponding 2-acetyl benzofuran 2 in good yield, on treatment with 1,8-diaza bicyclo[5.4.0]undec-7-ene (DBU) in the presence of molecular sieves. Further, aldol condensation with vanillin, Claisen-Schmidt condensation reaction with hydrazine hydrate followed by coupling of substituted anilines afforded target compounds. The structures of newly synthesized compounds were confirmed by IR, (1)H NMR, (13)C NMR, mass, elemental analysis and further screened for their antioxidant and antimicrobial activities. Among the tested compounds 5d and 5f exhibited good antioxidant property with 50% inhibitory concentration higher than that of reference while compounds 5h and 5l exhibited good antimicrobial activity at concentration 1.0 and 0.5 mg/mL compared with standard, streptomycin and fluconazole respectively.

Synthesis, antioxidant and antimicrobial activity of novel vanillin derived piperidin-4-one oxime esters: Preponderant role of the phenyl ester substituents on the piperidin-4-one oxime core

The study has been achieved the efficient synthesis of vanillin derived piperidin-4-one oxime esters (5a-m) via four step reaction involved Mannich reaction of vanillin, acetone and ammonium acetate to obtain 2,6-bis(4-hydroxy-3-methoxyphenyl)-piperidin-4-one 2 followed by N-methylation and oximation. Further, to enhance the biological activity of vanillin derived piperidin-4-one oxime core, esterification of 4 with substituted benzoyl chlorides in the presence of strong organic base t-BuOK accomplished a series of vanillin derived piperidin-4-one oxime esters (5a-m). The synthesized analogues are screened for their antioxidant and antimicrobial studies and the preponderant effect of the phenyl ester substituents on the biological activity of piperidin-4-one oxime core was demonstrated. Among the tested compounds, 5i and 5j are emerged as outperformed antioxidants than standard Butylated hydroxy anisole (BHA) whereas, compounds 5b and 5d manifested potent antibacterial and antifungal activity than standard streptomycin and fluconazole respectively.

Synthesis and antioxidant properties of some novel 5H-dibenz[b,f]azepine derivatives in different in vitro model systems.

A series of 5H-dibenz[b,f]azepine containing different aminophenols and substituted aminophenols were synthesized. 3-chloro-1-(5H-dibenz[b,f]azepine-5yl)propan-1-one (2) was obtained by N-acylation of 5H-dibenz[b,f]azepine (1) with 3-chloro propionyl chloride. Further base condensation with different aminophenols and substituted aminophenols to produce series of 5H-dibenz[b,f]azepine containing aminophenol and substituted aminophenol (2a-e). The structures of newly synthesized compounds were characterized by spectral and elemental analysis. Their antioxidant properties were evaluated by using several methods: scavenging effects on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, inhibition of lipid peroxidation using beta-carotene linoleate system, inhibition of human low-density lipoprotein (LDL) oxidation and reducing power. Butylated Hydroxy Anisole (BHA) and Ascorbic acid (AA) were used as the reference antioxidant compounds and also the comparative study with the synthesized compounds was done. Under our experimental conditions, Compound (2) showed negligible activity over all the antioxidant assays but 5H-dibenz[b,f]azepine containing different aminophenols and substituted aminophenols (2a-e) showed good antioxidant activities over all the methods and compounds containing substituted aminophenols 2e and 2d showed predominant antioxidant activities among the synthesized analogues.

Chemoselective Hydrogenation of Aromatic Nitro Compounds Using Diammonium Hydrogen Phosphite and Commercial Zinc Dust

The aromatic nitro compounds are reduced to their corresponding amines at room temperature in good yields by employing diammonium hydrogen phosphite as hydrogen donor and zinc as catalyst. The hydrogenation is fast and selective in the presence of the other sensitive functionalities such as halogens, -OH, -NH2, -OCH3, -CN, -COCH3, -COOH, -COOR etc. It was observed that, this system is equally competitive with existing methods.

In Vitro Antioxidant Activity of Dibenz[b,f]azepine and its Analogues

Dibenz[b,f]azepine and its five derivatives bearing different functional groups were synthesized by known methods. The compounds thus synthesized were evaluated for antioxidant potential through different in vitro models such as (DPPH) free radical scavenging activity, s-carotene-linoleic acid model system, reducing power assay and phosphomolybdenum method. Under our experimental condition among the synthesized compounds dibenz[b,f]azepine (a) and 10-methoxy-5H-dibenz[b,f]azepine (d) exhibited potent antioxidant activity in concentration dependent manner in all the above four methods. Butylated hydroxyl anisole (BHA) and ascorbic acid (AA) were used as the reference antioxidant compounds. The most active compounds like dibenz[b,f]azepine and its methoxy group substituent have shown more promising antioxidant and radical scavengers compared to the standards like BHA and ascorbic acid. It is conceivable from the studies that the tricyclic amines, i.e. dibenz[b, f]azepine and some of its derivatives are effective in their antioxidant activity properties.

Novel 2,6-bis(4-methoxyphenyl)-1-methylpiperidin-4-one oxime esters: synthesis and a new insight into their antioxidant and antimicrobial potential

A simple and efficient protocol for the synthesis of novel 2,6-bis(4-methoxyphenyl)-1-methylpiperidin-4-one oxime esters 4(a–q) is described. Initially, p-anisaldehyde 1 was condensed (Mannich reaction) with acetone and ammonium acetate trihydrate afforded 2,6-bis(4-methoxyphenyl)piperidin-4-one 2. Then, methylation followed by oximation with hydroxylamine hydrochloride (NH2OH∙HCl) furnished a key scaffold 4. Further, to explore the enhanced biological properties of the piperidin-4-one core i.e. the key scaffold 4 was conjugated with substituted benzoyl chlorides in the presence of anhydrous K2CO3 as base to obtain novel 2,6-bis(4-methoxyphenyl)-1-methylpiperidin-4-one oxime esters 4(a–q) in excellent yields. The newly synthesized compounds were characterized by elemental analysis, IR, 1H NMR, 13C NMR and mass spectroscopic techniques, and screened for their in vitro antioxidant and antimicrobial activities. Most of the compounds exerted positive efficacy towards the biological assays performed. Among the synthesized analogues, compounds 4l and 4m exhibited promising antioxidant activity and on the other hand compounds 4b and 4d manifested persuasive antibacterial activity, whereas compound 4b displayed stupendous antifungal activity against A. flavus strain.

DNA binding, anti-inflammatory and analgesic evaluation of metal complexes of N/S/O donor ligands; synthesis, spectral characterization.

Transition metal complexes containing tri-dentate NSN donor ligands i.e., 5-((1(aminomethyl)cyclohexyl)methyl)-1,3,4-thiadiazol-2-amine (AMTA) (2) and 5-(2-aminophenyl)-1,3,4-thiadiazol-2-amine (ATA) (4i-ii) have been synthesized. The newly synthesized ligands and their respective complexes were characterized by elemental analysis, molar conductance measurement and various spectral studies [infrared (IR), electronic, and NMR (for ligands only)]. Metal complexes are like [M(AMTA)2], [M(ATA)2] type, where M=Mn(II), Co(II) and Cu(II). The proposed geometries of the complexes are octahedral in nature. The synthesized ligands and their complexes were exhibits effective anti-inflammatory, analgesic and DNA binding activities. All the tested compounds exhibited significant analgesic activity, whereas the compound 4i, 4(ia) and 4(iib) is equipotent with Diclofenac sodium.

Synthesis of Amino Acid Analogues of 5H-Dibenz[b,f]azepine and Evaluation of their Radical Scavenging Activity

A method for the synthesis of tyrosine, phenyl alanine, hydroxy proline and threonine free amino acid analogues of 5H-dibenz[b,f]azepine is proposed. 5H-dibenz[b,f]azepine was prepared by known method. The key intermediate 3-chloro-1-(5H-dibenz[b,f]azepine-5-yl)propan-1-one was obtained by N-acylation of 5H-dibenz[b,f]azepine with 3-chloro propionyl chloride. Further coupling of respective free amino acid to produce 2-(3-(5H-dibenz[b,f]azepine-5-yl)-3-oxopropylamino)3-(4 hydroxyphenyl) propanoic acid, 2-(3-(5H-dibenz[b,f]azepine-5-yl)-3-oxopropylamino)-3-phenyl propanoicacid,1-(3-(5H-dibenz[b,f]azepine-5-yl)-3-oxopropyl)-3-hydroxypyrolidine-2-carboxylic acid and 2-(3-(5H-dibenz[b,f] azepine-yl)-3-oxopropyl amino)-3-hydroxy butanoic acid. The synthesized compounds were evaluated for their potential over 1,1-diphenyl-2-picryl hydrazyl (DPPH) free radical scavenging activity. Butylated hydroxy anisole (BHA) and ascorbic acid (AA) were used as the reference antioxidant compounds and also the comparative study with synthesized compounds was done. Under our experimental conditions tyrosine, hydroxy proline and threonine analogues possess a direct scavenging effect on trapping the stable free radical DPPH. Hydroxy proline analogues showed a significant radical scavenging activity among the synthesized analogues

Crystal and Molecular Structure Analysis of 1-Acryloyl-3-methyl-2,6-bis(3,4,5-trimethoxyphenyl)piperidine-4-one

The title compound C27H33NO8 crystallizes in the orthorhombic crystal class under the space group Pbca with cell parameters a = 13.775(4) Å, b = 16.389(2) Å, c = 23.085(6) Å, Z = 8, and V = 5212.6(3) Å3. The piperidine ring in the structure adopts a twist boat conformation. The bond lengths and bond angles are in good agreement with the standard values. The structure exhibits intermolecular hydrogen bond of the type C–H···O. The synthesized molecule was characterized by FT-IR, 1H-NMR, MS, and elemental analysis.

Synthesis of thiazole-based substituted piperidinone oximes: Profiling of antioxidant and antimicrobial activity

The synthesis of novel thiazole-based piperidinone oximes and screening of their antioxidant and antimicrobial activity are described. The obtained results revealed that the electronic effects of active substituents at C-4 terminals of phenyl rings on either side of piperidinone skeleton, as well as at 2-hydrazinyl thiazole, played a major role in development of antioxidant and antimicrobial activity. Antioxidant activity seems to be based also on radical dissipating ability of the thiazole ring. The nucleophilic character of sulfur in thiazole and lipophilic nature of piperidinone skeleton substantially influenced the observed antimicrobial activity of thiazole-based piperidinone oximes. Among the synthesized compounds, 2,6-bis(4-hydroxy-3-methoxyphenyl)-1-methylpiperidin-4-one O-(2-(2-(4-hydroxy-3-methoxybenzylidene)hydrazinyl)thiazol-4-yl) oxime exhibited excellent antioxidant activity whereas compound 2,6-bis(4-chloro phenyl)-1-methylpiperidin-4-one O-(2-(2-(4-nitrobenzylidene)hydrazinyl)thiazol-4-yl)oxime emerged as an outstanding antimicrobial agent.