Acid‐catalysed depurination of DI‐, TRI‐ and polydeoxyribonucleotides: Effect of molecular environment on the cleavage of adenine residue

First‐order rate constants for the acid‐catalysed cleavage of adenine base from 2′‐deoxyadenosine, its 3′ ‐ and 5′‐ monophosphates, various dinucleoside monophosphates, trinucleoside diphosphates and hexameric 2′‐deoxyadenylic acid were measured by the method of initial velocity. The results obtained were compared with the effect that hetroassociation with caffeine has on the pre‐equilibrium protonation and rate‐limiting heterolysis of 2′ ‐deoxyadenosine and its isosteric analogue, 1‐(2‐deoxy‐β‐D‐erythro‐pentofuranosyl) benzimidazole. The kinetics of the depurination of poly (dA‐T), poly(dA) and a mixture of poly(dA) and poly(T) were determined, and the rate variations observed are discussed on the basis of the known structures of these polymers.