Sundarababu Baskaran

A novel and efficient one-pot method has been developed for the synthesis of cyclopropane-fused bicyclic amidines on the basis of a CuBr2-mediated oxidative cyclization of carbanions. The usefulness of this unique multicomponent strategy has been demonstrated by the use of a wide variety of substrates to furnish novel cyclopropane-containing amidines with a quaternary center in very good yields. This ketenimine-based approach provides straightforward access to biologically active and pharmaceutically important 3-azabicyclo[n.1.0]alkane frameworks under mild conditions. The synthetic power of this methodology is exemplified in the concise synthesis of the pharmaceutically important antidepressant drug candidate GSK1360707 and key intermediates for the synthesis of amitifadine, bicifadine, and narlaprevir.

Functionalized indoles are synthezised under mild conditions in a tartaric acid-dimethylurea melt. The melt serves as the solvent and as the catalyst. Under these reaction conditions, sensitive functional groups such as N-Boc, N-Cbz, or azides are stable, and indolenines are obtained regioselectively in excellent yields. The practical use of the method is demonstrated in the synthesis of the hormone melatonin. © 2012 American Chemical Society.

The antibacterial drug ciprofloxacin (cfH) has been used to protect gold nanoparticles of two different mean diameters, 4 and 20 nm. The protection is complete with about 65 and 585 cfH molecules covering 4 and 15 nm particles, respectively. The nature of binding has been investigated by several analytical techniques. The nitrogen atom of the NH moiety of piperazine group binds on the gold surface, as revealed by voltammetric and spectroscopic studies. The cfH-adsorbed particles are stable in the dry state as well as at room temperature, and as a result, redispersion is possible. The rate of release of the drug molecule from the nanoparticles is more in the basic medium than in pure water, and the kinetics depend on the size of the particle; faster desorption is seen in smaller particles. The bound cfH is fluorescent, and this property could be used in biological investigations. This study shows that metal nanoparticles could be useful carriers for cfH and fluoroquinolone molecules. Most of the bound molecules could be released over an extended period of time.

Lapachol (1), a naphthoquinone isolated mostly from the plants of the bignoniaceae family has a broad spectrum of biological activities and as a consequence it has been the object of different chemical transformations. Lomatiol (3), another naturally occurring naphthoquinone having structural similarities to lapachol, has been obtained from chemical and microbial transformations of lapachol in very low yields. In the present study, an easy approach for the synthesis of lomatiol (3) from lapachol (1) has been developed using SeO2 oxidation in 90% yield. Lomatiol, under epoxidation conditions afforded novel furano- and pyrano-naphthoquinone derivatives, which are analogues of anticancer agents, 2-acetylfuronaphthoquinone and β-lapachone. Most of the structures were unambiguously confirmed by single crystal X-ray analysis.

A direct and mild route to formanilides from aromatic nitro compounds bearing different functional groups under catalytic transfer hydrogenation (CTH) conditions is described. © 2001 Elsevier Science Ltd.

A new method for the direct synthesis of β-chloro-N′- tosylamidines from olefins using chloramine-T and trifluoromethanesulfonic acid is described. © Georg Thieme Verlag Stuttgart - New York.

The N-formylation of secondary amines and anilines using ammonium formate as a formylating agent is described. (C) 2000 Elsevier Science Ltd.

A facile amination of quinolone carboxylic acids to fluoroquinolone antibacterials under microwave irradiation is described. © 2001 Elsevier Science Ltd. All rights reserved.

A highly facile and chemoselective method for the reductive N-formylation of aryl azides under catalytic transfer hydrogenation conditions is described. © 2002 Elsevier Science Ltd. All rights reserved.

A simple and efficient method for the stereoselective synthesis of isoxazoline/isoxazole-fused iminosugar derivatives has been developed using intramolecular nitrile oxide cycloaddition (INOC) as a key step. Iminosugar C-nitromethyl glycosides, derived from simple carbohydrates, served as excellent nitrile oxide precursors in 1,3-dipolar cycloaddition reactions. N-Alkenyl iminosugar C-nitromethyl glycosides afforded novel isoxazoline-fused indolizidine-, pyrrolizidine-, and quinolizidine-based iminosugars in excellent yields with a high degree of stereoselectivity, whereas N-alkynyl iminosugar C-nitromethyl glycosides furnished the corresponding isoxazole containing tricyclic iminosugars in very good yields.