Rajender S. Varma

Alumina-mediated deacetylation of benzaldehyde diacetates. A simple deprotection method

Abstract A simple, extremely fast, and high yielding method for the selective deprotection of benzaldehyde diacetates is described which occurs under mild conditions on neutral alumina surface. Gentle heating, using microwave irradiation or conventional methods facilitates the procedure.

The synthesis of radiolabeled compounds via organometallic intermediates

Utilisation de boranes, alanes, silanes, germanes, stannanes, de composes organiques du mercure, de thallates, de reactifs de Grignard, de composes organiques du lithium

Alumina-mediated cleavage of t-butyldimethylsilyl ethers

Abstract A simple method for the cleavage of t -butyldimethylsilyl ethers is described which occurs on alumina surface under solvent free conditions within 10–15 minutes. Mild heating, using microwave irradiation facilitates the procedure.

Alumina-mediated microwave thermolysis : a new approach to deprotection of benzyl esters

Abstract A simple and high yielding method for deprotection of benzyl esters is described which occurs under mild and solvent-free conditions on alumina surface using microwave irradiation.

Alumina-mediated condensation. A simple synthesis of aurones

Abstract A simple and high yielding synthesis of aurones (2-phenylmethylene-3 (2H)-benzofuranones) is described which occurs under mild conditions on alumina surface using readily available benzofuranones and arylaldehydes.

Growth inhibitory effects of bioflavonoids and related compounds on human leukemic CEM-C1 and CEM-C7 cells

Seven compounds, which included some naturally occurring dietary substances, were tested for their inhibitory effects on growth and metabolism of human leukemic CEM-C1 and CEM-C7 cell lines. Among the active compounds the naturally occurring dietary constituents were found to be the most active. The strongest inhibitory effects were observed with 3,4,5,7-tetrahydroxy-flavone (luteolin) and 4,4-dihydroxychalcone. 31P-NMR spectra of cells incubated for 24 h with 30 microM of either of these compounds show complete ATP depletion. Also glucose uptake by the cells as measured by 13C-NMR is completely inhibited by these compounds. These results may be relevant to the tumor suppressing activity of bioflavonoids and the role of these compounds in chemoprevention.

SELECTED REDUCTIONS OF CONJUGATED NITROALKENES

Conjugated nitroalkenes are readily reduced by a variety of borane and borohydride reagents. The reactions provide a convenient access to a number of nitrogen and oxygen based functional groups.

2.1 – Reduction of Nitro and Nitroso Compounds

Nitro compounds are versatile synthetic intermediates which have found widespread utility in industrial applications. Aromatic nitro compounds are the usual starting materials for commercial applications, but aliphatic compounds exhibit a greater diversity of chemical behavior under reducing conditions.1–4 Nitroso compounds, hydroxylamines, oximes, amines, nitrones, ketones and silyl nitronates are frequently encountered during the reduction of nitro compounds. Several specialized reviews have appeared which highlight the versatility of the nitro group in organic chemistry.1–8

Ruthenium tetraoxide catalyzed oxidation of nucleosides: A facile synthesis of 5′-carboxylic acid derivatives

Abstract Purine and pyrimidine nucleosides have been oxidized to the corresponding 5′-carboxylic acids using potassium persulfate and ruthenium trichloride under basic conditions. The method provides easy access to nucleosides bearing 3′-amino and 5′-carboxylic acid functionalities from 3′-azido compounds as exemplified by oxidation of AZT followed by reduction of the acid.

Ruthenium tetraoxide: a mild reagent for the oxidation of 2′,3′-O-isopropylidene purine nucleosides

Abstract 2′,3′-O-isopropylidene purine nucleosides have been oxidized with ruthenium tetraoxide to provide the corresponding 5′-carboxylic acids in quantitative yields under neutral conditions.