Synthesis of new annellated flavonoid derivatives possessing spasmolytic activity--VII

7,8-Dihydroxyflavone reacts with ethyl 2,3-dibromopropanoate to form the new, annellated, 1,4-benzodioxanes 1 containing a flavone structural unit. The regioisomers 1a and 1b thus obtained were separated and 1a was converted to the amides 2a-2f. The constitutions of 1 and 2 were elucidated by 500 MHz 1H-NMR spectroscopy. In the spasmolysis test, 2e showed significant antagonistic effect towards the agonists acetylcholine, barium chloride, and histamine.