School Of Pharmaceutical Sciences :: Faculty of Pharmaceutical Sciences

A. Pre-Doctoral Research :

Carried out research work under Dr. R. N. Chakraborty, D. Sc., F.N.A., F.A.S .. the then Professor of Chemistry, School of Tropical Medicine, Calcutta on various Medicinal Plants.
Isolated and characterised a large number of phytochemicals such as sterols, triterpenes, glycosides, sapogenins etc.
Worked on the structure - activity relationship of well known pharmacophore and synthesised a large number of compounds possessing considerable antifungal activity.
Applied Friedel - Craft reaction on a new haloacylchloride and synthesised a new series of compounds having potential insecticidal activities.
Developed a new and convenient method of synthesis of aromatic :-keto aldehydes by application of Friedel-Craft Reaction and controlled hydrolysis of the products thereof. Resulting products have been found to posses antiviral activity effective against influenza virus.
In recognition of my works in Medicinal Chemistry under the guidance of Prof. R. N. Adhya; the then Head of the Department of Chemistry, Calcutta School of Tropical Medicine, I was awarded the Doctorate of Philosophy Degree of Calcutta University.
B. POST DOCTORAL RESEARCH:
Firedel crafts reaction is one of the most useful reactions in organic chemistry and has been studied extensively for more than a century that encompasses the preparation of diverse types of compounds by alkylaytion, acylation, cyliacylation and other miscellaneous types of reactions. It is well-known that when substrates are employed in unimolar proportions in Friedel-crafts reaction normal products are obtained and their mechanism of formation is well understood.
In an attempt to synthesise polynuclear compounds by applying Friedel-crafts acylation reaction we contemplated that if the substrate is used in higher proportion, the normal reaction products that would be obtained might further act with the substrate giving rise to polynuclear compounds. We also presume an ingenuous development of the reaction condition that might depend on the nucleophilicity of the substrate and the electrophilicity of the acyl carbonyl group of the initially formed acylated product.
This presumption was, indeed, found to be feasible and could be demonstrated for the first time that when excess amounts of substrates are used interesting polynuclear compounds are formed as secondary reaction products. The works on mono-substituted benzenes e.g. anisole and phenetole with dichloroacetyl chloride in presence of anhydrous Alel3 demonstrates that our contemplation is correct and it opens' an enormous futuristic approach of Friedel-crafts reaction which was once considered static after its long history of 110 years. [Friedel-Crafts Chemistry: A New Synthetic Route for polynuclear compound; S.B. Mahato, N.R Mondal, A. K. Pal and S. K. Moitra ; Journal of Organic Chemistry. 49. 718-20, 1984].
The replication of our novel findings in a wider range, based on disubstituted benzenes e.g. dimethyl resorcinol, m-xylene, m-methyl m-chlorotoluene etc. affirmed our idea on a concrete base and demonstrates the role of the substrate governing the mechanism of the Friedel-crafts reaction and has been unambiguously investigated by way of synthesising structurally unique polynuclear compounds [Novel Friedel-Crafts Reactions of Some Arenes ; S. B. Mahato, N. B. MandaI, A. K. Pal, & S.K. Moitra ; Tetrahedron vol. 43, No. 19, PP 4439 to 4445, 1987].
We were intrigued by this new found knowledge and attempted to synthesise differently substituted choride and different pairs of substituted benzenes. Monosubstituted benzenes of varying nucleophilicity e.g. Toluene, chlorobenzene, anisole, phenetole etc. were used as model substrates for initial formation of acylated product which were reacted in situ with uni or bimolar proportion of other substituted benzenes to 'yield differently substituted di or polymeric products.
The highly exciting results may be considered as a new tool for target synthesis of this new class of compounds and is notable for its generality, preparative simplicity and conceptual novelty [A Novel Application of the Friedel-Crafts Reaction to the synthesis of Differently Substituted Polynuclear compounds. S.B. Mahato, N.B. Mandai, A.K. Pal, S.K. Moitra, C. Lehman and P. Luger; Journal of Organic Chemistry, 1988, 53, 5554-5558].
Characterisation of the products were done by using modern instrumental technique viz 1 HNMR, 13 CNMR, IR, Mass spectra, X-ray crystallography and also by classical chemical methods.
C. RESEARCH IN ANALYTICAL CHEMISTRY:
A study on the analysis of various cough syrups attracted the attention of analytical scientists over the last ten years. A comparison between reversed phase and silica methods of similar cough syrup demonstrates that peak responses obtained by the aqueous silica method are more symmetric than the reversed phase methods. I order to unambiguously ascertain the influence of surface silanols, the author studied a combination of diphenhydramine and chlorpheniramine in cold syrup. The retention of the compounds increased with the increase of the mobile phase pH (0-11). The pH of the mobile phase can also affect the peak shape in aqueous silica methods. Difference in solvation, which depends on the degree of protonation, has been cited as a possible explanation. The resulting research publication has been extensively reviewed in "Chramatographic Analysis of Pharmaceuticals," Ed. John A. Adamsvics, Second Edition, Vol. 74 (Chromatographic Science Series), Marcel Decker Inc., New York, 1997.
Antiamaebic formulations containing Iodochlorohydroxyquinoline / Diiodohydroxyquinoline / Tinidazole / Diloxanide Furoate were extensively studied with a view to develop simple but facile analytical methods for use in QC Laboratorics.

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