Effect of Ionic State of 2'-Deoxyguanosine and Solvent On Its Aralkylation By Benzyl Bromide

To extend studies of the aralkylation of nucleic acid components under a variety of solvent conditions, we determined product distributions from the reactions of benzyl bromide with 2'-deoxyguanosine and the anion of 2'-deoxyguanosine in 2,2,2-trifluoroethanol (TFE) and compared these distributions with those from the reaction of the anion with benzyl bromide in N'\N-dimethylacetamide (DMA). 7-Benzylguanine was the only benzylated product detected in the reaction with the neutral nucleoside in TFE, In striking contrast, the reaction of the anion of 2'-deoxyguanosine with benzyl bromide in TFE produced N-2-benzyl-2'-deoxyguanasine in significant yield and with high selectivity. The reaction of the anion of 2'-deoxyguanosine with benzyl bromide in DMA produced products derived only from reaction at the 1- and/or 7-position of the nucleoside. The weakly nucleophilic but protic polar solvent TFE and the iminolate tautomeric form of the 2'-deoxyguanosine anion appear to be essential for benzylation at the exocyclic N-2-position. [References: 28]

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