Ph.D Theses

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Browsing Ph.D Theses by Subject "Chemistry"

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    Inverse Electron Demand Diels Alder Reaction of Pyrido[1,2-a]pyrimidine 2-ones - Experimental and Theoretical Investigation and Antibacterial Activity of Synthesized Adducts
    (2023-03) Abinaya A; Dr. V.Sharulatha
    The IEDDA reaction of diene 2-oxo-2H-pyrido[1,2-a] pyrimidin-3(4H)-ylidiene acetic acid with various electron rich dienophiles in DMF medium yielded moderate to good yields in the presence of Lewis acid catalyst indium (III) chloride. FT-IR, 1H NMR, 13C NMR, and Mass Spectroscopy investigations were used to characterize and confirm the structures of all the synthesized adducts. Except for 3-butoxy-9-methyl-2,3,4,5 tetrahydropyrano[2,3-d]pyrido[1,2-a]pyrimidine-4-carboxylic acid (5) and Methyl-2-Oxo-1 Phenyl-1,2,3,3a,4,5-hexa hydropyrazolo[1,5-b]Pyrido[1',2':1,2]Pyrimido[5,4 e][1,2]Oxazine-4-Carboxylic Acid (7) which showed 1:1 and 6:4 ratio and for other adducts the ratio was found to be 6:1, supporting the endo rule. The analysis of the LUMO and HOMO energies of diene and dienophiles helped to prove the IEDDA reaction pathway. NBO charges computed using DFT techniques gave justification for the regioselectivity provided by the reaction. The synchronous nature of the transition states and intrinsic reaction coordinates of the reaction of diene 2-oxo-2H-pyrido[1,2-a] pyrimidin-3(4H) ylidiene acetic acid with dienophiles butyl vinyl ether and 1-methyl-1-cyclohexene by DFT method explained the observed diastereoisomeric ratio of 1:1 and 6:1 endo and exo ratio respectively. All synthesized compounds were tested for antibacterial activity, which showed moderate activity, however the compound 3a-methyl 2-oxo-1-phenyl-1,2,3,3a,4,5-hexahydropyrazolo[1,5-b]pyrido[1',2':1,2]pyrimido[5,4 e][1,2]oxazine-4-carboxylic acid was shown to be more powerful in both in-silico and in vitro investigations.
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    Synthesis, Computational Assessment and Biological Evaluation of 2-Amino-1,3,4-thiadiazoles and their Azo Derivatives
    (Avinashilingam, 2024-09) Kiruthika S; Dr. V. Sharulatha
    The development of new series of heterocycles has continued to support the growth of organic chemistry and pharmaceutical industry. The expansion of new and potent bio-active nitrogen and sulfur containing heterocycles was a constant requirement in the pharmaceutical industry. A search for potent anti-bacterial agents provoked us to design and synthesis 2-amino-1,3,4-thiadiazoles and their azo derivatives. The 2-amino-1,3,4-thiadiazoles were synthesized from eight different heterocyclic acids and thiosemicarbazide using concentrated sulphuric acid, p-toluene sulphonic acid and silica supported sulphuric acid catalysts. Silica supported catalyst yielded higher amount than other two catalysts. Amino group of thiadiazoles were converted into azo group by two couplers viz resorcinol and β-naphthol via conventional method resulting in excellent yields. Synthesized compound’s structures were elucidated by FTIR, UV-visible, 1H NMR, 13C NMR, mass spectroscopy and elemental analysis. DFT calculations were used to divulge the geometry optimization, quantum chemical descriptors, molecular electrostatic potential map and NBO analysis. Molecular docking analysis were performed against two proteins namely AgrA LytTR Domain of Staphylococcus aureus and LasR-TP1 complex of Pseudomonas aeruginosa. The highest docking score was found for compounds substituted with quinoline and β-naphthol rings. According to the in silico ADMET analysis all the compounds showed a good drug likeness property. The anti-bacterial activity was screened against Staphylococcus aureus and Pseudomonas aeruginosa. The target compounds with quinoline and β-naphthol substitution showed significant inhibitory activities against both the tested organisms than others. Moreover, these compounds exposed a correlation between experimental and theoretical predictions. The study provides basis for further in vivo and clinical trials of anti-bacterial activity.