7-SUBSTITUTED 7-DEAZA-2'-DEOXYGUANOSINES - REGIOSELECTIVE HALOGENATION OF PYRROLO[2,3-D]PYRIMIDINE NUCLEOSIDES

The synthesis of 7-chloro-, 7-bromo-, and 7-iodo-substituted 7-deaza-2 '-deoxyguanosine derivatives 2b-d is described. The regioselective 7-h alogenation with N-halogenosuccinimides was accomplished using 7-[2-de oxy-3,5- formylamino)-4-methoxy-7H-pyrrolo[2,3-d]pyrimidine (4) as the common precursor. A one-pot reaction (2N aq. NaOH) of the halogenated intermediates 5a-c furnished the desired compounds. Also the 7-hexyny l derivative 2e of 7-deaza-2'-deoxyguanosine is described.