Modified in the base

Due to the importance of modified nucleosides that are also in the base, the development of new biocatalytic processes appUed to the synthesis of derivatives modified in the base is of great interest Adenosine deaminase (ADA) and adenylate deaminase (AMPDA) are biocatalysts that catalyze the hydrolytic deaminahon of purine nucleosides and nucleotides. Some applications of these deaminases for the preparation and transformation of compounds structurally related to nucleosides with potential antitumor and antiviral activities have been described in the last few years [8]. 

The inhibitors of DNA polymerases have been found among dNTP derivates modified in the base (2-substituted dATP and I P-substituted dGTP analogs, derivatives with altered base-pairing specificity), derivates modified in the sugar (arabinonu-cleotides, 2, 3 -dideoxynucleotides, acyclonucleotides) and derivates modified in the triphosphate group (for example, phosphorothioates of dATP) [31-33]. 

Reversed-phase h.p.l.c. - thermospray m.s. analyses of radiation induced decomposition products of thymine and thymidine, which are modified in the base moiety, and of 2, 3 -dideoxycytidine in plasma have been reported. 

The 3 -deoxy-pyrazolo[3,4-d]pyrimidine nucleoside (27) has been prepared by conventional coupling,and various 3 -deoxyinosine analogues modified in the base unit were synthesized from guanosine by free radical deoxygenation of a 2, 5 -di-0-TBDMS derivative.63... 

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