Novel Lapachol Derivatives and Their Antioxidant Activity

A convenient synthesis of the new enamine derivatives 2-diethylamino-3-(3-methyl-2-butenyl)-1,4-naphthalenedione (2), 2-ethylamino-3-(3-methyl-2-butenyl)-1,4-naphthalenedione (3), 2-diethanolamino-3-(3-methyl-2-butenyl)-1,4-naphthalenedione (4), and 2-(1-piperazinyl)-3-(3-methyl-2-butenyl)-1,4-naphthalenedione (5) was carried out from natural 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphtalenedione (lapachol, 1) and diethylamine, ethylamine, diethanolamine and piperazine, respectively. All products were fully characterized by IR, 1H and 13C NMR spectroscopy. Results revealed no antioxidant behavior for 1 and enamines 2 and 3, but antioxidant activity for enamines 4 and 5.