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The syntheses of 1,7-dideaza-2',3'-dideoxyadenosine (1) and related pyrrolo [2,3-b]pyridine 2',3'-dideoxyriboand 2',3'-didehydro-2',3'-dideoxyribonucleosides (see 2-5) are described. As starting materials, 2'-deoxyribonucleosides 6 or 7 were used. The 3'-OH group was removed by Burton deoxygenation or via mesylation followed by elimination and catalytic hydrogenation. Compound 1 was also obtained from the direct glycosylation of 4-nitro-lH-pyrrolo[2,3-b]pyridine (17) with the 2,3-dideoxyribofuranosyl chloride 18. The triphosphate 25 of 1 showed only marginal activity against HIV-1 reverse transcriptase, indicating that purine N(l) is required for the inhibitory activity of the parent 2',3'-dideoxyadenosine.

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The synthesis of the imidazo[1,2‐a]pyrimidine 2′‐deoxyribonucleosides 2a and 3a related to 2′‐deoxyguanosine or 2′‐deoxyinosine is described. Glycosylation of the nucleobase anion of 5 with 2′‐deoxy‐3,5‐bis‐O‐(4‐methylbenzoyl)‐α‐D‐erythro‐pentofuranosyl chloride (6) yielded stereoselectively the N‐1 β‐D‐deoxyribofuranoside 7. Under the same conditions the 2′,3′‐dideoxyrihalogenoses 11 and 14 were employed to afford anomeric mixtures of glycosylation products (12, 13 and 15, 16). The glycosylation products obtained from the 2′‐deoxyribo‐ and 2′,3′‐dideoxyribo halides were then converted into the final nucleosides (2a, b and 3a, b). The inhibitory activity of the imidazo[1,2‐a]pyrimidine 2′,3′‐dideoxynucleoside 5′‐triphosphates 28a and 28b against HIV reverse transcriptase was tested.