SYNTHESIS OF BIOLOGICALLY ACTIVE XANTHENE AND NAPHTHOFURAN DERIVATIVES

Abstract

A large variety of natural products of biological importance contain xanthenes and bcnzoxanthenes as an integral part of their structures. Xanthenes are of great interest in organic synthesis owing to their various biological activities, their application in photodynamic therapy and their use as dyes and fluorescent materials for visualizing biomolecules. The arenofurans are well known for their antibacterial, antiviral, anticancer, mutagenic, antifertility activities. They act as inhibitors of hepatocyte nuclear factor 4-alpha, agonist for nicotinic acetylcholine receptor and inhibitor of nuclear transcription factor kappa-3. Keeping the importance of these heterocycles in mind, we have developed a methodology for the synthesis of these compounds using simple, mild, efficient and cost effective catalysts. The cheap, easily available and easily removable silica sulphuric acid has been used as catalyst for the solvent-free synthesis of dibenzoxanthesnes. The reaction procedure is quite simple, rapid and dibenzoxanthenes are formed exclusively in good yields. We have demonstrated basic alumina as a novel promoter for the coupling of f3-naphthols and 3-nitrostyrenes to afford naphthofurans in good to high yields under solvent-free conditions. The simplicity of experimental procedure and ready availability of catalyst and starting materials render this an experimentally attractive method for the synthesis of naphthofurans. The reaction of anaphthol with -nitrostyrenes is less effective and produced the corresponding naphthofurans in low yields. This may be attributed for the less reactivity of f3-position of a-naphthol in comparision to that of a-position of I3-naphthol. All the compounds were fully characterized by analytical tools and by comparison of the known data for the available compounds.