Synthetic Studies of C-15 and C-17 Compounds

- A new synthesis of 4-methyl-3-phenyl and 3-phenyl-4-styryl coumarins developed by condensing substituted o-hydroxyacetophenones and 2'-hydroxychalcones with phenyl acetic acid or its 4-methoxy derivative in the presence of DCC-DMSO - 2'-Hydroxy-?-cinnamylidene acetophenones undergo facile oxidative cyclisation to the corresponding 2-styryl chromone on treatment with potassium iodate–DMSO - A new convenient method for the benzylation of chelated phenolic groups in various substrates developed by using benzyl chloride-acetone-anhydrous potassium carbonate with tetra-n-butylammonium iodide catalyst (quantitative yields) - 2'-Benzyloxy-?-cinnamylidene acetophenones were converted to their epoxideswhich on treatment with BF3-etherate afforded the corresponding 3-styryl chromones - 2'-Hydroxy-?-cinnamylidene acetophenones gave the corresponding 3-hydroxy-2-styryl chromones on treatment with hydrogen peroxide- diethylamine in DMSO-dioxan - In the 13C-NMR spectral studies of 2'-hydroxy-?-cinnamylidene acetophenones the four olefinic carbons were assigned diagnostic and definite ? values.