Tapas Sarkar

Bacopaside I and II: two pseudojujubogenin glycosides from Bacopa monniera.

Two saponins, designated as bacopaside I and II, have been isolated from Bacopa monniera Wettst. and their structures have been elucidated as 3-O-alpha-L-arabinofuranosyl-(1-->2)-[6-O-sulphonyl-beta-D-glucopyranosyl-(1-->3)]-alpha-L-arabinopyranosyl pseudojujubogenin (1) and 3-O-alpha-L-arabinofuranosyl-(1-->2)-[beta-D-glucopyranosyl (1-->3)]-beta-D-glucopyranosyl pseudojujubogenin (2) mainly on the basis of 2D NMR and other spectral analyses.

Carbazole alkaloids from roots of Glycosmis arborea

Abstract A new carbazole alkaloid, designated as glycoborinine, was isolated from the roots of Glycosmis arborea , along with two other known carbazole alkaloids, viz. glycozoline and glycozolidine, and two known quinoline alkaloids, viz. skimianine and 3- (3′,3′-dimethylallyl)-4,8-dimethoxy- N -methylquinolin-2-one. Its structure was elucidated mainly on the basis of its 2D NMR spectral analyses.

A new bisbenzylisoquinoline alkaloid isolated from Thalictrum foliolosum, as a potent inhibitor of DNA topoisomerase IB of Leishmania donovani

Chemical investigation of the stem of Thalictrum foliolosum resulted in the isolation of two new bisbenzylisoquinoline alkaloids (1 and 2) along with known protoberberine group of isoquinoline alkaloids thalifendine (3) and berberine (4). The structures of the new compounds were established by detailed 2D NMR spectral analysis with their configurations determined from their optical rotation values and confirmed using circular dichroism. Inhibitory activities of these four compounds against DNA topoisomerase IB of Leishmania donovani were evaluated. Compound 2 exhibited almost complete inhibition of the enzyme activity at 50 μM concentration and it was found to be effective in killing both wild type as well as SAG resistant promastigotes of the parasite.

Synthesis of furo[3,2- c ]coumarin from the reaction of 3-halochromone and 2-aminochromone; 2-aminochromone as a masked 4-hydroxycoumarin

Synthesis of 2-(2-hydroxybenzoyl)-4H-furo[3,2-c]chromen-4-one has been accomplished by the reaction of 3-halochromone with 2-aminochromone. In this reaction, 2-aminochromone acts as a masked 4-hydroxycoumarin.

Design and synthesis of dichromeno[2,3-b;3′,2′-e]pyridine-12,14-dione to evaluate its optical properties

An unambiguous synthesis of dichromeno[2,3-b;3′,2′-e]pyridine-12,14-diones has been developed under mild conditions and their optical properties have been evaluated by studying UV-vis absorption and photoluminescence (PL) spectroscopy, cyclic voltammetry (CV) measurements, DFT calculations and thermogravimetric analysis.