Reaction of the potent bacterial mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) with 2'-deoxyadenosine and calf thymus DNA: identification of fluorescent propenoformyl derivatives.

The potent bacterial mutagen and drinking water disinfection byproduct 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) was reacted with 2'-deoxyadenosine and calf thymus DNA in aqueous solutions at neutral conditions. HPLC analyses of the 2'-deoxyadenosine reaction mixtures showed that two previously unidentified products were formed. The products were isolated by preparative C18 chromatography, and their structures were characterized by UV absorbance, fluorescence emission, 1H and 13C NMR spectroscopy, and mass spectrometry. It was concluded that in both products a propeno bridge had been incorporated between N-1 and N6 of the adenine unit. In one of the products, the propeno bridge carried a formyl group [3-(2'-deoxy-beta-D-ribofuranosyl)-7H-8-formyl[2,1-i]pyrimidopurine++ + (pfA-dR)], and in the other the substituents consisted of a formyl group and a chlorine atom [3-(2'-deoxy-beta-D-ribofuranosyl)-7H-8-formyl-9-chloro[2,1-i]pyrimid opurine (Cl-pfA-dR)]. These novel adducts exhibited fluorescence in the visible region with emission maxima around 460 nm. The yields of the products in reactions performed at pH 7.4 and 37 degrees C were about 0.03 mol %. In reaction of MX with calf thymus DNA, the adduct pfA-dR was formed and its yield was about 0.6 adduct/10(5) nucleotides.