Isolation, structure, and synthesis of hermidin, a chromogen from Mercurialis perennis L.

Abstract

Hermidin has been isolated from Mercurialis perennis L. as a colourless, crystalline compound, shown by synthesis to be 5-hydroxy-4-methoxy-1-methylpyridine-2,6(1H,3H)-dione (2), which in aqueous solution exists as a dihydroxy-4-methoxy-1-methylpyridin-2(1H)-one (3) or (4). Oxidation of hermidin with nitric acid affords 4-methoxy-1-methylpyridine-2,3,6-trione (16). When equimolecular amounts of the latter and hermidin in aqueous solution are mixed an immediate deep blue solution containing an ion-radical (17) results. Oxidation of hermidin by air in methanolic solution gives 5,5′-dihydroxy-4,47′-dimethoxy-1,1′-dimethyl-3,3′-bipyridine-2,2′,6,6′-(1H,1′H,3H,3′H)-tetraone (18). and in pyridine solution 4,4′-dimethoxy-1,1′-dimethyl-3,3′-bipyridine-2,2′,5,5′,6,6′-hexaone (23). Knackmuss' conclusions on the oxidation of 3,6-dihydroxy-4-methylpyridin-2(1H)-one (26) have been re-interpreted. 3,4-Dihydroxy-5-methoxy-1-methylpyridin-2(1H)-one (7) has been synthesized.