UNCATALYZED HYDROLYSIS OF DEOXYURIDINE THYMIDINE AND 5-BROMODEOXYURIDINE

The N-glycosyl bonds of deoxyuridine, thymidine, and 5-bromodeoxyuridine undergo slow hydrolysis in aqueous solution, pH 3-7. The reaction rates are independent of the pH in this range, and of the nature and concentration of the buffer. The reactions have positive entropies of activation. A linear correlation exists between the logarithms of the rate constants for the three nucleosides and the ionization constants for the 1-protons of the corresponding bases. It is proposed that the reaction involves a simple SnI ionization mechanism. The existing data on the known acidcatalyzed hydrolyses of these nucleosides is reexamined. It has been considered that the acid-catalyzed hydrolyses of nucleosides proceeds via sugar ring opening to an intermediate immonium ion. It is suggested that an A-l mechanism, analogous to the hydrolysis in neutral solution, might better fit the data for deoxyuridine derivatives. © 1969, American Chemical Society. All rights reserved.