New observations concerning the chloroacetaldehyde reaction with some tRNA constituents. Stable intermediates, kinetics and selectivity of the reaction

Abstract

The stable intermediates formed in the reaction of cytosine, cytidine and adenosine with chloroacetaldehyde were isolated. The -CH2CH/OH/- bridge between the exo and endo nitrogen atoms of the parent base was found in these compounds by means of PMR spectroscopy. Their acid-induced dehydration resulted in formation of appropriate ethenoderivatives. The rate constants of the intermediate formation and its dehydration were found to be 38×10-4 and 47×10-4 /min-1/ for adenosine, and 33×10-4 and 10×10-4 /min-1/ for cytidine. The pH range of 4.5 - 5.0 was found to be optimum for both adenosine and cytidine reactions. The quantitative modification of these two nucleosides in the presence of guanosine may be achieved with high selectivity only at a low pH of 3.0 - 4.0. N6-methyladenosine and N4-methylcytidine react quantitatively with chloroacetaldehyde and the reaction rate is higher than in the case of the parent nucleosides. The structure of the reaction products was assigned on the basis of PMR spectroscopy. © 1978 Information Retrieval Limited.