A series of novel spiro-substituted 4-hydroxypyranocoumarins and their corresponding dihydropyrano cis-diols has been synthesized. Among them the spiroadamantylpyranocoumarin and the diols can interact with the stable free radical 1, 1- diphenyl-2-picrylhydrazyl and scavenge superoxide anions generated in the xanthine– xanthine oxidase system.