Regioselective Syntheses of 7-Halogenated 7-Deazapurine Nucleosides Related to 2-Amino-7-deaza-2′-deoxyadenosine and 7-Deaza-2′-deoxyisoguanosine

Abstract

The syntheses of 7-halogenated derivatives 3b-e of 2-amino-7-deaza-2'-deoxyadenosine as well as 7-bromo and 7-chloro-7-deaza-2'-deoxyisoguanosines 4b-c are described. Nucleobase anion glycosylation was employed for the convergent nucleoside synthesis. The regioselective 7-halogenation was performed either on the nucleoside precursor 7 or on the nucleobase 12. Two bromo substituents were introduced in the 7- and 8-position when the unprotected 2-amino nucleoside 9 was used. Conformational analysis of the sugar moiety of nucleosides 3a-e and 4a-c was performed on the basis of vicinal 1 H, 1 H NMR coupling constants.