Natural product chemistry, 140. Synthesis of some new acridones

Abstract Methyl 6‐amino‐2,3‐dimethoxybenzoate ( 6 ) which was obtained from 6‐formyl‐2,3‐dimethoxybenzoic acid ( 1 ), was treated with phloroglucinol to give two new acridone alkaloids, 1,3,8‐trihydroxy‐7‐methoxy‐9‐acridone ( 7 ) and 1,3‐dihydroxy‐7,8‐dimethoxy‐9‐acridone ( 8 ). Methylation of 7 and 8 gave another four new acridone alkaloids, 1,8‐dihydroxy‐3,7‐dimethoxy‐9‐acridone ( 9 ), 1,8‐dihydroxy‐3,7‐dimethoxy‐10‐methyl‐9‐acridone ( 10 ), 1‐hydroxy‐3,7,8‐trimethoxy‐10‐methyl‐9‐acridone ( 11 ) and 1,3,7,8‐tetramethoxy‐10‐methyl‐9‐acridone ( 12 ).