Browsing by Author "Alka Agarwal"

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1-Prop-2-ynyl-1H-benzimidazol-2-amine
(2011) Alka Agarwal; Manavendra K. Singh; Satish K. Awasthi
In the title compound, C10H9N3, the benzimidazol-2-amine and CH2 -C≡CH units are not coplanar, with a dihedral angle of 60.36°between their mean planes. The crystal structure is stabilized by intermolecular N-H⋯N hydrogen bonding and π-π interactions [centroid-centroid distances 3.677 (1) and 3.580 (1) Å], assembling the molecules into a supra-molecular structure with a three-dimensional network.
2-(4-Chlorophenyl)chromen-4-one
(2011) Shailja Singh; Manavendra K. Singh; Alka Agarwal; Satish K. Awasthi
The title compound, C15H9ClO2, is a synthetic flavonoid obtained by the cyclization of 3-(4-chloro-phen-yl)-1-(2-hy- droxy-phen-yl)prop-2-en-1-one. The 4-chloro-phenyl ring is twisted at an angle of 11.54°with respect to the chromen-4-one skeleton. In the crystal, pairs of molecules are interconnected by weak Cl⋯Cl interactions [3.3089 (10) Å] forming dimmers which are further peripherally connected through intermolecular C-H⋯O hydrogen bonds..
(2E)-1-(4-Amino-phen-yl)-3-(2,4-dichloro-phen-yl)prop-2-en-1-one
(2011) Shailja Singh; Manavendra K. Singh; Alka Agarwal; Firasat Hussain; Satish K. Awasthi
The title compound, C 15H 11C l2NO, is approximately planar (r.m.s. deviation = 0.062 Å) and contains a single C=C double bond in a trans (E) configuration. The crystal packing is stabilized by intermolecular N - H⋯N and N - H⋯O inter-molecular hydrogen bonding. © Singh et al. 2011.
An efficient and economical synthesis of 5-substituted 1 H -tetrazoles via Pb(II) salt catalyzed [3+2] cycloaddition of nitriles and sodium azide
(Elsevier Masson SAS, 2016) Rama Kant; Vishal Singh; Alka Agarwal
A simple, mild and efficient method is developed for the synthesis of 5-substituted 1H-tetrazoles. Out of three used Pb(II) catalysts, lead chloride (PbCl2) has been found to be an efficient catalyst for [3+2] cycloaddition of NaN3 with aromatic and aliphatic nitriles to afford 5-substituted 1H-tetrazoles. The catalyst is reusable up to four cycles with consistent activity. The cost effectiveness and easy availability of the catalyst, simple methodology, excellent yield and easy work-up are the additional advantages. © 2015 Académie des sciences.
An expedient approach to 1,2-dihydroisoquinoline derivatives via cobalt catalysed 6-endo dig cyclization followed by Mannich condensation of o-alkynylarylaldimines
(Royal Society of Chemistry, 2015) Urvashi; Gaurav K. Rastogi; Sandeep K. Ginotra; Alka Agarwal; Vibha Tandon
A highly effective 6-endo dig cyclisation of o-alkynylaldimines to 1,2-dihydroisoquinolines has been described via direct and nitro Mannich condensation using inexpensive and readily available cobalt chloride as catalyst. This strategy provides an effective procedure for the synthesis of substituted 1,2-dihydroisoquinolines derivatives in moderate to high yields. An addition of pronucleophiles, such as nitromethane, acetone and α-hydroxyacetone, to o-alkynylarylaldimines has been achieved via isoquinolinium intermediate. This journal is © The Royal Society of Chemistry.
Anchoring CuO nanoparticle on nitrogen-doped reduced graphene oxide as nanocatalyst for the synthesis of 5-substituted-1H-tetrazole and 1,2,3- triazole derivatives
(Elsevier B.V., 2023) Alka Singh; Alka Agarwal
A basic and proficient newer method was exploited for the preparation of CuO-NrGO nanoparticles which was characterized by state of art instruments i.e. Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), Energy dispersive X-ray (EDX), Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), Thermo gravimetric analysis (TGA) and UV-visible spectroscopy. The prepared heterogeneous nanoparticle possesses a significant level of catalytic activity for the production of two diversified series i.e.5-substituted-1H-tetrazole and 1,2,3-triazole derivatives in excellent yield (92% and 95% respectively) with minimal catalyst loading. CuO-NrGO nanoparticles showed reusability up to seven repetitions without any significant loss (11% in 5-substituted-1H-tetrazole and 10.3% in 1,2,3-triazole derivatives) of catalytic activity and productivity. © 2023 Elsevier B.V.
Benzyl N-(3-chloro-4-fluorophenyl)-carbamate
(2011) Manavendra K. Singh; Alka Agarwal; Satish K. Awasthi
The title compound, C14H11ClFNO2, the phenyl ring (A), the chlorofluorophenyl ring (B) and the central ketone O/C/O group (C) are not coplanar, with dihedral angles B/C = 31.6 (2), A/B = 21.3 (2) and A/C = 50.1 (2)°. The crystal packing is stabilized byN-H⋯O and C-H⋯O interactions.
Challenges and Recent Advances of Novel Chemical Inhibitors in Medulloblastoma Therapy
(Humana Press Inc., 2022) Anand Maurya; Upendra Kumar Patel; Jitendra Kumar Yadav; Virender Pratap Singh; Alka Agarwal
Medulloblastoma is a common term used for the juvenile malignant brain tumor, and its treatment is exciting due to different genetic origins, improper transportation of drug across the blood-brain barrier, and chemo-resistance with various side effects. Currently, medulloblastoma divided into four significant subsections (Wnt, Shh, Group 3, and Group 4) is based on their hereditary modulation and histopathological advancement. In this chapter, we tried to combine several novel chemical therapeutic agents active toward medulloblastoma therapy. All these compounds have potent activity to inhibit the medulloblastoma. © 2022, The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.
Ciprofloxacin-Tethered 1,2,3-Triazole Conjugates: New Quinolone Family Compounds to Upgrade Our Antiquated Approach against Bacterial Infections
(American Chemical Society, 2022) Alka Agarwal; Preeti Singh; Anand Maurya; Upendra Kumar Patel; Alka Singh; Gopal Nath
A newer ciprofloxacin series containing 1,2,3-triazole conjugates of ciprofloxacin was designed, synthesized, and well characterized using modern analytical techniques by reacting diversified anilines with ciprofloxacin obtained from ciprofloxacin hydrochloride. The newer conjugates were evaluated for their antimicrobial activity against various strains, viz. Staphylococcus aureus (ATCC25923), Enterococcus faecalis (clinical isolate), Staphylococcus epidermidis (ATCC3594), Escherichia coli (ATCC25922), Pseudomonas aeruginosa (ATCC27853), Salmonella typhi (clinical isolate), Salmonella typhimurium (clinical isolate), Acinetobacter baumannii (ATCC19606), Aeromonas hydrophila (ATCC7966), Plesiomonas shigelloides (ATCC14029), and Sphingo biumpaucimobilis (MTCC6362) in vitro. Interestingly, some of the conjugates showed superior antimicrobial activity as compared to the control drug ciprofloxacin. The three compounds 4i, 4j, and 4n showed strong activity with minimum inhibitory concentration (MIC) 0.78 μM, while the compound 4g showed MIC 1.56 μM against S. typhi (clinical). The compound 4a showed good efficacy against S. aureus (ATCC25923) and S. typhi (clinical) with MIC 3.12 μM, while the compound 4b exhibited efficacy with MIC 3.12 μM against S. aureus (ATCC25923) and the control drug ciprofloxacin showed MIC 6.25 μM. Among all of the synthesized compounds, 4e, 4f, 4g, 4h, 4p, 4q, 4t, and 4u displayed less than 20% hemolysis, while the rest of the compounds showed hemolysis in the range of 21–48%. Moreover, the structure of compound 4b was also established by single-crystal X-ray diffraction studies. © 2022 The Authors. Published by American Chemical Society
Crystallographic, Thermal and Hirshfeld Surface Studies of N-(1H-1,3-benzodiazol-2-yl)benzamide
(Springer India, 2017) Vishal Singh; Rama Kant; Alka Agarwal
In present study, the compound N-(1H-1,3-benzodiazol-2-yl)benzamide was synthesized and characterized by 1H NMR, IR, elemental and X-ray analysis. A good quality single crystal was grown by slow evaporation solution growth technique to investigate their X-ray structure. The compound crystallizes in a triclinic crystal system with space group P-1 and having the unit cell parameters of a = 10.2350(5) Ǻ, b = 14.7494(7) Ǻ, c = 24.2813(11) Ǻ, α = 79.084(4) °, β = 83.927(4) °, γ = 80.039(4) °, V = 3534.8(3) Å3and Z = 12. The molecules are arranged in a linear manner and crystal packing is stabilized by N–HO, N–HN, C–HO, C–H and intermolecular interactions. These interactions generate various hydrogen bond patterns e.g. R21(6), R22(10), R22(8), R21(7) and R44(30). Hirshfeld surface analysis suggests that the intermolecular HH, CH, NH and OH contacts are predominant. The thermal behavior of crystal was determined by DSC and TGA analysis. © 2017, The National Academy of Sciences, India.
Design, synthesis and antimicrobial activity of novel benzothiazole analogs
(2013) Manavendra K. Singh; Ragini Tilak; Gopal Nath; Satish K. Awasthi; Alka Agarwal
In an attempt to design and synthesize a new class of antimicrobials, dialkyne substituted 2-aminobenzothiazole was reacted with various substituted aryl azides to generate a small library of 20 compounds (3a-t) by click chemistry. Structures of the newly synthesized compounds were established on the basis of spectral data. These compounds were screened for their antibacterial activity against Gram+ bacteria (Staphylococcus aureus and Enterococcus faecalis), Gram- bacteria (Salmonella typhi, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Shigella boydii) and antifungal activity against Candida tropicalis, Candida albicans, Candida krusei, Cryptococcus neoformans) as well as molds (Aspergillus niger, Aspergillus fumigatus). The compound 3e showed maximum potency against all Gram+/gram- bacterial strains with MIC value 3.12 μg/ml, which is two fold more active as compared to standard drug ciprofloxacin (MIC 6.25 μg/ml). However, all compounds were found ineffective against S. boydii (clinical isolate). Further, only one compound 3n was found to be the most active against all fungal strains with MIC value in the range of 1.56 μg/ml-12.5 μg/ml while the remaining compounds showed moderate to weak antifungal activity. © 2013 Elsevier Masson SAS. All rights reserved.
Design, synthesis and biological evaluation of ciprofloxacin tethered bis-1,2,3-triazole conjugates as potent antibacterial agents
(Elsevier Masson SAS, 2016) Rama Kant; Vishal Singh; Gopal Nath; Satish Kumar Awasthi; Alka Agarwal
A series of new bis-1,2,3-triazole linked ciprofloxacin conjugates was designed, synthesized and evaluated in vitro antibacterial activity against a panel of clinically relevant bacteria. A significant part of the compounds displayed enhanced activity against both Gram-positive and Gram-negative species of bacteria as compared to the parent drug. Additionally, negligible toxicity profile of compounds indicates that they may act a good antibiotic in future. Despite relatively small number of synthesized conjugates, it was possible to observe important dependences between their structure and activity. © 2016 Elsevier Masson SAS
Efficient: N -formylation of primary aromatic amines using novel solid acid magnetic nanocatalyst
(Royal Society of Chemistry, 2020) Jitendra Kumar Yadav; Priyanka Yadav; Satish K. Awasthi; Alka Agarwal
Sulfonic acid functionalized over biguanidine fabricated silica-coated heterogeneous magnetic nanoparticles (NP@SO3H) have been synthesized, well characterized and explored for the first time, as an efficient and recyclable catalyst for N-formylation of primary amines under mild reaction conditions. Exploiting the magnetic nature of Fe3O4, the prepared catalyst was readily recovered from the reaction mixture via an external magnet. The catalyst can be reused for up to six cycles without any substantial loss of catalytic activity. The cost effectiveness, simple methodology, wide substrate tolerance, excellent yield and easy work-up are the additional advantages of present catalytic system. This journal is © The Royal Society of Chemistry.
Hydrogen bonding patterns and DFT studies of (4-Acetylphenyl)amino 2,2-Dimethylpropanoate and (E)-1-(4-aminophenyl)-3-[4-(dimethylamino)phenyl] prop-2-en-1-one
(Springer New York LLC, 2014) Rama Kant; Biswajit Maiti; Satish Kumar Awasthi; Alka Agarwal
The (4-acetylphenyl)amino 2,2-dimethylpropanoate (1) and (E)-1-(4-aminophenyl)-3-[4-(dimethylamino)phenyl]prop-2-en-1-one (2), were synthesized and characterized by elemental analysis, FT-IR, 1H NMR, 13CNMR and single crystal X-ray diffraction techniques. Both compounds 1 and 2 crystallized in orthorhombic crystal system with Pbca and P212121 space group respectively, having the unit cell parameters: a = 11.7220(12) Å, b = 14.4580(13) Å, c = 15.7853(12) Å, β = 90°, Volume = 2675.2(4) Å3, Z = 8 for 1 and a = 6.1146(5) Å, b = 9.0567(8) Å, c = 26.079(3) Å, β = 90°, Volume = 1444.2(2) Å3, Z = 4 for compound 2. The crystal structures of both compounds (1 and 2) are stabilized by N-H···O strong intermolecular hydrogen bonding forming C 1 1 (8) motifs. In compound 1, the molecules are linked by three C-H···O intramolecular H-bond forming S(6) motifs. In compound 2, the molecules are linked by C-H···N intermolecular H-bond exhibiting C 1 1 (12) motif and C-H···O intramolecular H-bond leading to S(5) motif. Crystallographic and vibrational data are compared with the results of density functional theory (DFT) method at the B3LYP/6-31G(d,p) level. The electronic (UV-vis) spectra was calculated by using the TD-DFT method and correlated with experimental spectra. © 2014 Springer Science+Business Media New York.
In vitro antimicrobial activity of o-phenylenediamine-tert-butyl-N-1,2,3-triazole carbamate analogs
(Birkhauser Boston, 2014) Manavendra Kumar Singh; Mayank Gangwar; Dharmendra Kumar; Ragini Tilak; Gopal Nath; Alka Agarwal
In an attempt to design and synthesize effective antimicrobial agents using click chemistry, mono- and di-alkyne-substituted monoboc protected o-phenylenediamines were reacted with different substituted aryl azides which yielded 18 new compounds (4a-4k and 5a-5f, 5l). Structures of all newly synthesized compounds were established by 1H and 13C NMR analysis. The intermediate compound 1 was also confirmed by X-ray crystallography. The title compounds were screened for their antibacterial activity against Gram +ve bacteria (Staphylococcus aureus and Enterococcus faecalis), Gram -ve bacteria (Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa), and their antifungal profile were tested on (Candida tropicalis , Candida albicans, Candida krusei, and Cryptococcus neoformans) as well as on molds such as (Aspergillus niger, Aspergillus fumigatus). The compounds 4k and 5f both showed maximum potency against S. aureus (ATCC 25323) strain with MIC value of 6.25 μg/ml, which is comparable with standard drug ciprofloxacin (MIC 6.25 μg/ml) while remaining compounds showed moderate to weak activity. Further, all compounds showed average antifungal activity in the range of 100-200 μg/ml. © Springer Science+Business Media New York 2014.
In vivo antifilarial activity of some cyclic and acylic alcohols
(2011) Alka Agarwal; Satish K. Awasthi; P.K. Murthy
The filarial nematodes, Wuchereria bancrofti, Brugia malayi, and Brugia timori are the causative agents of lymphatic filariasis. 2-Substituted propanol, cyclohexanol, and cyclooctanol compounds were evaluated for microfilaricidal and macrofilaricidal activity in vivo against Acanthocheilonema viteae and Litomosoides carinii in rodents. In the cyclohexanol series, 2-(piperidin-1-yl) cyclohexanol (2b) showed 88.9% macrofilaricidal activity against A. viteae in vivo, while cyclooctanol series, 2-(4- benzyl piperdin-1-yl) cyclooctanol (2f) showed 100% macrofilaricidal activity against A. viteae. Further, compounds 1-(furan-2-ylamino) ethanol (4a) and 1-(4-benzylpiperidin- 1-yl)-ethyl acetate (5b) showed 81.3% and 83.4% macrofilaricidal activity, respectively, against the same parasite. Interestingly, compounds 2f and 4a showed significant sterilization of female worms in A. viteae. However, these compounds were found inactive against L. carinii. Therefore, the new class of compounds appeared to have promising antifilarial activity. © 2011 Springer Science+Business Media, LLC.
Inherent Flexibility vis-à-vis Structural Rigidity in Chemically Stable Antimalarial Dispiro N-Sulfonylpiperidine Tetraoxanes
(Wiley-Blackwell, 2018) Chiranjeev Sharma; Kumkum Sharma; Jitendra Kumar Yadav; Alka Agarwal; Satish Kumar Awasthi
Structurally diverse and chemically stable tetraoxanes were formed by peroxidation of N-sulfonylpiperidones. X-ray analysis revealed that the crystal structures possess central spiro-2,5-disubstituted tetraoxane rings trans fused to 6-membered piperidine and cyclohexylidene substituents in classical chair conformations. The more flexible cycloheptane ring exhibited pseudorotation between chair and twist chair conformation. The two sulfonyl oxygen atoms act as hydrogen-bonding acceptors and participate in hydrogen bonding. Docking calculations showed that the tetraoxanes are aligned parallel to the plane of the porphyrin ring of heme so that the iron can attack the O−O bond to initiate redox-mediated reaction to render nanomolar antimalarial potency to these compounds against P. falciparum 3D7. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Insight into the interaction of benzothiazole tethered triazole analogues with human serum albumin: Spectroscopy and molecular docking approaches
(John Wiley and Sons Ltd, 2019) Priyanka Yadav; Jitendra Kumar Yadav; Arvind Kumar Dixit; Alka Agarwal; Satish Kumar Awasthi
The interaction of four benzothiazole tethered triazole analogues (MS43, MS70, MS71, and MS78) with human serum albumin (HSA) was investigated using various spectroscopic techniques (ultraviolet–visible (UV–vis) light absorption, fluorescence, circular dichroism (CD), molecular docking and density functional theory (DFT) studies). Fluorescence quenching constants (~1012) revealed a static mode of quenching and binding constants (Kb ~104) indicating the strong affinity of these analogues for HSA. Further alteration in the secondary structure of HSA in the presence of these analogues was also confirmed by far UV–CD spectroscopy. The intensity loss in CD studied at 222 nm indicated an increase in random coil/β-sheet conformations in the protein. Binding energy values (MS71 (−9.3 kcal mol−1), MS78 (−8.02 kcal mol−1), MS70 (−7.16 kcal mol−1) and MS43 (−6.81 kcal mol−1)) obtained from molecular docking revealed binding of these analogues with HSA. Molecular docking and DFT studies validated the experimental results, as these four analogues bind with HSA at site II through hydrogen bonding and hydrophobic interactions. © 2019 John Wiley & Sons, Ltd.
Insights into the interaction of potent antimicrobial chalcone triazole analogs with human serum albumin: Spectroscopy and molecular docking approaches
(Royal Society of Chemistry, 2019) Priyanka Yadav; Jitendra Kumar Yadav; Alka Agarwal; Satish K. Awasthi
Mechanistic insights into the interaction of five previously chemically synthesized triazole-linked chalcone analogs (CTs) with human serum albumin (HSA) were sought using various spectroscopic techniques (UV-visible absorption, fluorescence, and circular dichroism) and molecular docking. The fluorescence quenching experiments performed at three different temperatures (288, 298 and 308 K) revealed the static mode of quenching and the binding constants (Kb ∼ 106-9) obtained indicated the strong affinity of these analogs for HSA. Furthermore, significant changes in the secondary structure of HSA in the presence of these analogs were also confirmed by far UV-CD spectroscopy. The thermodynamic properties such as the enthalpy change (ΔH°), Gibbs free energy change (ΔG°) and entropy change (ΔS°) revealed that the binding process was spontaneous and exothermic. Theoretical studies, viz., DFT and molecular docking corroborated the experimental results as these five analogs could bind with HSA through hydrogen bonding and hydrophobic interactions. The present study provides useful information regarding the interaction mechanism of these analogs with HSA, which can provide a new avenue to design more potent chalcone triazole analogs for use in the biomedical field. © The Royal Society of Chemistry 2019.
Is structural hybridization invoking new dimensions for antimalarial drug discovery research?
(Royal Society of Chemistry, 2023) Bhawana Sharma; Alka Agarwal; Satish Kumar Awasthi
Despite effective prevention methods, malaria is a devastating, persistent infection caused by protozoal parasites that result in nearly half a million fatalities annually. Any progress made thus far in the eradication of the disease is jeopardized by the expansion of malaria parasites that have evolved to become resistant to a wide range of drugs, including first-line therapy. To surmount this significant obstacle, it is necessary to develop newly synthesized drugs with multiple modes of action that may have a novel target in various stages of Plasmodium parasite development and this is made possible by the hybridization concept. Hybridization is the combination of at least two diverse pharmacophore units with some linkers bringing about a single molecule with a diverse mode of action. It intensifies a drug's physiological and chemical characteristics, such as absorption, cellular target contact, metabolism, excretion, distribution, and toxicity. This review article outlines the currently published most potent hybrid drugs against the Plasmodium species. © 2023 RSC.