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2,6‐Diaminopurine and guanine 2′‐deoxynucleosides substituted with a fluoromethyl, methyl, vinyl, ethyl, or azido group at the C‐4’ position of the sugar moiety 1–10 were synthesized and their activity against HIV and HBV were determined. 4′‐Fluoromethyl and 4′‐methyl derivatives 1 and 2, respectively, were synthesized by glycosidation of the 4′‐substituted sugars 11 and 12, respectively, using 2,6‐diaminopurine, followed by deoxygenation of the 2′‐hydroxyl group. 4′‐Vinyl analog 3 was synthesized from 4′‐hydroxymethylnucleoside 19, and 4′‐ethyl derivative 4 was obtained by hydrogenation of 3. 4′‐Azide analog 5 was synthesized by SNAr reaction of guanine derivative 23 with ammonia. Nucleosides 1–5 were converted to the corresponding guanine derivatives 6–10 using adenosine deaminase. Some of these compounds exhibited substantial to potent anti‐HIV and HBV activity with generally favorable cytotoxicity profiles.

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Encouraged by our recent findings that 4′-cyano-deoxyguanosine (2), entecavir analogues 4 and 5 are highly potent anti-hepatitis B virus (HBV) agents, we designed and synthesized 6 having a hybridized structure of 4 and 5.