Synthesis of 3-methoxy-5-hydroxy-3 ',4 '-methylenedioxy-6 '',6 ''-dimethylpyrano [2 '',3 '': 7,8]flavone
3-Methoxy-5-hydroxy-3', 4'-methylenedioxy-6'', 6"-dimethylpyrano[2", 3" : 7, 8]flavone 7 has been synthesised from phloroacetophenone 1. Phloroacetophenone 1 on treatment with chlorobutyne (2-chloro-2-methylbut-3-yne) in dry dioxan yields 2, 6-dihydroxy-6', 6'-dimethylpyrano[2', 3' : 4, 3]acetophenone 2 which on treatment with methoxymethyl chloride affords 2, 6-di (methoxymethoxy)-6, 6'-dimethylpyrano[2'', 3" : 4', 3']acetophenone 3. Alkaline condensation of 3 with piperonal gives 2', 6'-di (methoxymethoxy)-3, 4-methylenedioxy-6", 6"-dimethylpyrano[2", 3" : 4', 3']chalcone 4. Demethoxymethylation of 4 affords 2, 6-dihydroxy-3, 4-methylenedioxy-6", 6"- dimethylpyrano[2", 3" : 4', 3']chalcone 5. Chalcone 5 on treatment with H2O2 in pyridine furnishes 3, 5-dihydroxy-3', 4'-methylenedioxy-6", 6"-dimethylpyrano[2", 3" : 7, 8]flavone 6. Finally partial methylation of 6 gives 3-methoxy-5-hydroxy-3', 4'-methylenedioxy-6", 6"- dimethylpyrano [2", 3" : 7, 8]flavone 7. All the new products have been characterised by the spectral data and elemental analysis.<