Formation of ethenocarbaldehyde derivatives of adenosine and cytidine in reactions with mucochloric acid

Mucochloric acid, a genotoxic compound formed during chlorine disinfection of drinking water, was reacted with adenosine and cytidine at pH 4.0, 90 degrees C. HPLC analyses with UV detection at 325 nm showed that one previously unidentified product peak was formed in each reaction. The products were separated and isolated by HPLC and characterized by UV absorbance, 1H and 13C NMR spectroscopy, and mass spectrometry. The products were identified as 3-(beta-D-ribofuranosyl)-7-formylimidazo[2,1-i]purine (I) and 6-(beta-D-ribofuranosyl)-3-formylimidazo[1,2-c]pyrimidin-5(6H)-one (II) (ethenocarbaldehyde derivatives of adenosine and cytidine, respectively). The ethenocarbaldehyde derivative of adenosine was also produced in reactions carried out at pH 7.4 and 37 degrees C. The formation of the ethanocarbaldehyde derivatives and the previously identified etheno derivatives from mucochloric acid is explained by an initial conversion of mucochloric acid, through hydrolysis and decarboxylation, to chloromalonaldehyde. Chloromalonaldehyde reacts with the nucleosides and forms an intermediate adduct which either undergoes ring closure by intramolecular displacement of the chlorine atom or breaks down to form chloroacetaldehyde which subsequently produces the etheno derivatives.