Studies on Xanthine Derivatives. I. Formation of Tricyclic Heterocycles from Hydrolysates of 1-(5-Oxohexyl) theobromine (Pentoxifylline)

Abstract

1-(5-Oxohexyl) theobromine (I) in alkaline solution was hydrolyzed by heating to give 4-(methylamino)-1-methyl-5-(5-oxohexyl) aminocarbonylimidazole (II) and N-[4-(5-carboxy-1-methylimidazolyl)]-N-methyl-N'-(5-oxohexyl) urea (III). When acidified with HCl, II and III were cyclized to 4, 4a, 5, 6, 7, 8-hexahydro-10-oxo-1, 4, 4a-trimethyl-1H-pyrido [1, 2-a]-purine (IV) and 4, 5, 7, 8, 9, 10-hexahydro-5, 12-dioxo-1, 4, 10a-trimethyl-1H-pyrido [2', 1' : 2, 3]-imidazo [4, 5-f] oxadiazocine hydrochloride (V), respectively.