A. Ravi Kumar

Stereoselective synthesis of (-)-cytoxazone

Abstract A novel stereoselective synthesis of (−)-cytoxazone 1 was achieved via addition of p -methoxyphenylmagnesium bromide to the benzylimine derived from ( S )-2,3- O -isopropylidene glyceraldehyde followed by one-step regioselective cyclization of N -Boc amino diol 7 .

A new approach to (-)-anisomycin

Abstract An efficient approach to enantiomerically pure (+)-deacetylanisomycin 2a and a formal synthesis of (+)-anisomycin 2 (11% overall yield in 10 steps) have been achieved through simple and good yielding reactions, starting from 1,2:3,4:5,6-tri-O-isopropylidene- d -mannitol 3. Grignard reaction and intramolecular cyclisation reactions are key steps in the strategy.

A short, simple and general approach for the synthesis of (3S, 4S)-3-methoxy-4-methylamino pyrrolidine and (3S, 4R)-3-methoxy-4-methylamino pyrrolidine

A general and efficient stereoselective approach for the synthesis of (3S,4S) and (3S,4R)-3-methoxy-4-methylamino pyrrolidines, a part of the structure of AG-7352, a naphthyridine antitumor agent and quinoline antibacterial compounds has been described.

An efficient synthesis of protected (2R,3R,4S)-4,7-diamino-2,3-dihydroxyheptanoic acid, a constituent of callipeltins A and D

Abstract An efficient and stereoselective synthesis of protected (2 R ,3 R ,4 S )-4,7-diamino-2,3-dihydroxyheptanoic acid, a constituent of the depsipeptides, callipeltins A and D, from d -ribose is described.

Copper-catalyzed three-component synthesis of aminonaphthoquinone-sulfonylamidine conjugates and in vitro evaluation of their antiproliferative activity.

A series of aminonaphthoquinone-sulfonylamidine conjugates were synthesized via a copper-catalyzed three-component reaction of N-propargyl aminonaphthoquinone, sulfonyl azides and various amines. Majority of the compounds exhibited promising antiproliferative potential when evaluated against a panel of four cancer cell lines. Docking experiments of representative compounds indicated that the conjugates can occupy the ATP-binding pocket of topoisomerase-II enzyme.

Design and synthesis of positional isomers of 1-alkyl-2-trifluoromethyl-5 or 6-substituted benzimidazoles and their antimicrobial activity

A series of novel positional isomers of 1-alkyl-2-trifluoromethyl benzimidazole derivatives 3a–j and 4a–j have been synthesized and screened for antibacterial activity against gram positive bacteria viz, Bacillus subtilis, Staphylococcus aureus and gram negative bacteria viz., Escherichia coli, Pseudomonas aeruginosa and antifungal activity against Candida albicans, Aspergillus niger, Rhizopus oryzae and Saccharomyces cerevisiae. Results indicate that compounds 3b, 4b were having promising antibacterial and antifungal activity.

Synthesis of novel optically pure α-amino acid functionalised-7-trifluoromethyl substituted quinolone derivatives and their antibacterial activity

Abstract7-Trifluoromethyl-4-hydroxy quinoline-3-carboxylic acid ethyl ester was prepared from 3-amino benzotrifluoride and EMME. The hydroxyquinoline was reacted with amino acids to furnish amino acid funtionalised quinolines (5, 6, 7). The compounds were alkylated by ethyl iodide followed by hydrolysis afforded the title compounds in good yields. They were screened for their antibacterial activity for in vitro against Gram +ve and Gram −ve bacterial strains and found 11e and 11b as promising compounds.

Note An efficient FeCl 3 catalyzed synthesis of β-keto enol ethers under solvent-free microwave irradiation condition

β-Keto enol ethers have been extensively used as key intermediates in organic synthesis 1-5 . For example, they have been used for the preparation of enantiomerically pure compounds 6 . β-Keto enol ethers are generally prepared starting from βdiketones by treatment with diazomethane 5 , with alcohols and p-toluenesulfonic acid at reflux 4 , methoxide 2,3 , iodine 7 , TiCl4 in methanol 8 and B(C6H5)3 (Ref. 9). However, some of these methods are associated with certain drawbacks such as multistep procedure, costly reagents, harsh reaction conditions, complex experimental process, long reaction times and low yields. Thus several previous methods have been excluded from practical applications due to environmental and economic considerations. Therefore, there is still the need to develop a facile, quicker, high yielding and nonpolluting preparation of β-keto enol ethers. Ferric chloride has been used as an efficient catalyst for several transformations 10,11 . In recent years, an elegant method of rapid heating by microwave irradiation has been applied in organic synthesis 12,13 . Additionally, microwave assisted reactions are novel, more efficient, convenient and provide solvent-free conditions. As part of the existing program aimed at developing new selective and environment friendly methodologies 13-15 for preparation of fine chemicals, it is wished to report herein another catalytic activity of FeCl3 for the efficient synthesis of β-keto enol ethers under solvent free microwave irradiation conditions.