Oxidation–reduction in hydrolysis of pyrimido[4,5-b]quinoline-2(3H),4(10H)diones (5-deazaflavins)

Abstract

Treatment of pyrimido[4,5-b]quinoline-2(3H), 4(10H)-diones (5-deazaflavins) with concentrated aqueous potassium hydroxide led to the exclusive formation of 1,5-dihydro-5-deazaflavins and 1,5-dihydro-5-deazaflavin-5-ones via intermolecular oxidation–reduction between initially formed 5-hydroxy-1,5-dihydro-5-deazaflavins and unchanged 5-deazaflavins; under dilute alkaline conditions reverse oxidation–reduction between 1,5-dihydro-5-deazaflavins and 1,5-dihydro-5-deazaflavin-5-ones occurred to form the original 5-deazaflavins and 5-hydroxy-1,5-dihydro-5-deazaflavins, which were oxidized into 1,5-dihydro-5-deazaflavin-5-ones by air.