Syntheses, DNA intercalation activities and molecular modelling on structures of tatramethyldifuronaphthalenes

2 , 7-Dialkoxynaphthalene (2) formed from the condensation of 2 , 7-dihydroxynaphthalene (1) with 3-chloro-2-butanone , refluxed in POCl₃/CCl₄ to give cyclized products of 73% asymmerical 4 and symmetrical tetramethyldifuronaphthalene 5. In the presence of hydrochloride , 2 was partly cyclized to give 3 , followed by cyclization at room temperature in acetylacetate/methylenechloride under the action of BBr₃ to give only symmetrical product 5. The structures of all products was fully characterized using IR , UV , FL , ¹H NMR , ¹³C NMR , MS and elementary analysis. It was found that 4 can intercalate into Calf Thymus DNA , but 5 couldn' t , and the apparrent intercalation constant for 4 was recorded. Using molecular modelling study , not only the bond lengths and angles of 5 were calculated well , but also it is indicated that the difference in DNA intercalation activity between 4 and 5 mainly depends on that in their molecular planarity.