REGIOSELECTIVITY OF THE MANNICH REACTION ON PYRROLO[2,3-D]PYRIMIDINE NUCLEOSIDES RELATED TO 7-DEAZA-2'-DEOXYADENOSINE OR 7-DEAZA-2'-DEOXYGUANOSINE

Mannich reactions were performed on 7-deazapurine 2'-deoxyribonucleosi des and the regioselectivity was studied. 7-Deaza-2'-deoxyadenosine (2 '-deoxytubercidin, 4a) furnished the 7-substituted Mannich base 5a. Th e side chain was introduced in the 8-position when 7-deaza-2 '-deoxygu anosine was used (Mannich base 7a). The regioselectivity changed back from position 8 to 7 when the reaction was performed on 4-methoxy-2-me thylthio-7H-pyrrolo[2,3-d]pyrimidine 2'-deoxyribonucleoside (12). Thus a 7-substituted Mannich product of 7-deaza-2 '-deoxyguanosine could b e obtained after demethylation and oxidation of the methylthio group f ollowed by displacement of the oxidized 2-substituent with ammonia.