Rajagopal Nagarajan

Synthesis of pyrido[2,3-b]indoles and pyrimidoindoles via Pd-catalyzed amidation and cyclization.

Biologically and pharmaceutically active core structures containing a new class of 4-hydroxy-α-carbolines, dihydropyrido[2,3-b]indoles, pyrimido[4,5-b] and [5,4-b]indoles have been synthesized in good yields via Pd-catalyzed amidation and cyclizations. The keto-enol tautomerism in 4-hydroxy-α-carbolines has been investigated by DFT calculations and spectroscopic techniques. The fluorescence studies of pyrimido[4,5-b] and [5,4-b]indoles were carried out with good quantum yields.

Deep eutectic solvent mediated synthesis of quinazolinones and dihydroquinazolinones: synthesis of natural products and drugs

A mild and greener protocol was developed to synthesize substituted quinazolinones and dihydroquinazolinones via deep eutectic solvent (DES) mediated cyclization with a series of aliphatic, aromatic, and heteroaromatic aldehydes in good to excellent yields. This greener strategy was further utilised to synthesize various quinazolinone natural products and drugs.

Total synthesis of cruciferane via epoxidation/tandem cyclization sequence

The total synthesis of alkaloid cruciferane is performed in three steps with an overall yield of 60.3%. The key step involves the in situ epoxidation of indole followed by tandem Cyclization via epoxide ring opening to furnish the 3-hydroxypyrroloindoline skeleton. This methodology gave a step economical and protecting group free total synthesis of cruciferane.

Zinc triflate catalyzed regioselective synthesis of pyrrolo[2,3-c]carbazoles via heteroannulation

We explored the zinc triflate catalyzed heteroannulation reaction of 3-aminocarbazoles with substituted propargyl alcohols to form pyrrolo[2,3-c]carbazoles in moderate to good yields. This transformation proceeds with good regioselectivity and without the addition of additives or ligands.

NIS-mediated regioselective amidation of indole with quinazolinone and pyrimidone

A mild, metal-free condition was developed for the direct regioselective C2 amidation of indoles and pyrroles with quinazolinone and pyrimidone derivatives in intermolecular fashion, which led to novel indolyl/pyrrolyl quinazolinone and pyrimidone derivatives in moderate to good yields.

Copper catalysed synthesis of indolylquinazolinone alkaloid bouchardatine

AbstractWe describe the total synthesis of indolylquinazolinone alkaloid bouchardatine and some of the quinazolinone derivatives. The aerobic oxidation induced by copper(I) bromide, followed by Vilsmeier-Haack formylation gives the natural product bouchardatine alkaloid in good yield. Graphical Abstract2,3-Dihydroquinazolin-4(1H)-ones are an important class of privileged compounds which have a range of applications in many areas of chemistry and frequently found in many natural products. The aerobic oxidation induced by copper(I) bromide, followed by Vilsmeier-Haack formylation gives the natural product bouchardatine alkaloid in good yield.

Concise total synthesis of water soluble metatacarboline A, C, D, E and F and its anticancer activity

The simple, concise, protecting group free and first total synthesis of Metatacarboline alkaloids (abbreviated as Mc) Mc A, C, D, E and F are reported. The core structure of metatacarboline alkaloids has been constructed by the classical Wittig reaction as key step from easily accessible starting materials with 40-75% overall yields. These synthesized compounds have been subjected to evaluate for their anticancer activity using C6 glioma cell lines. Mc D and Mc F showed significant antiproliferative activity, which was confirmed by MTT and Clonogenic assay. FACS analysis showed that Mc D and Mc F arrested the cell cycle at sub G0/G1 and G2/M phase of cell cycle respectively. Further, Western blot analysis and immunohistochemistry of Mc D treated cells revealed activation of caspase dependent downstream signaling which led to apoptosis.

Formal total synthesis of calothrixin B and its N-benzyl analogues

A formal total synthesis of calothrixin B and its N-benzyl analogues has been accomplished from (2-chlorophenyl)boronic acid, 8-bromophenanthridine-7,10-dione and benzylamines. The synthesis involves Suzuki cross-coupling and copper-catalyzed domino reactions to generate N-benzylcalothrixins in good to moderate yields.

Synthesis of pyrano[2,3-c]carbazoles, pyrano[3,2-b]carbazoles and furo[3,2-b]carbazole derivatives via iodocyclization

AbstractA simple and facile synthesis of pyranocarbazole derivatives starting from easily accessible O-propargylated carbazoles using iodocyclization in good yields is reported. Graphical AbstractA simple and facile synthesis of pyranocarbazole derivatives starting from easily accessible O-propargylated carbazoles using iodocyclization is reported.

Total synthesis of sannanine and analogues thereof

The first total synthesis of Sannanine has been accomplished with an overall 30% yield in a concise manner. The key strategies involve Friedländer quinoline synthesis, demethylation, in situ oxidation and amination process.Graphical AbstractThe first total synthesis of Sannanine has been accomplished with an overall 30% yield in a concise manner. The key strategies involve Friedländer quinoline synthesis, demethylation, in situ oxidation and amination processes.