A Convenient Method for the Synthesis of 2′,3′-Didehydro-2′,3′-Dideoxy Nucleosides

9-(2,3-Dideoxy-β-D-glyceropent-2-enofuranosyl)adenine (2′,3′-didehydro-2′,3′-dideoxyadenosine, 9a), 9-(2,3-dideoxy-β-D-glyceropent-2-enofuranosyl)hypoxanthine (2′,3′-didehydro-2′,3′-dideoxyinosine, 9b) and 4-amino-7-(2,3-dideoxy-β-D-glyceropent-2-enofuranosyl)pyrrolo[2,3-d]pyrimidine (2′,3′-didehydro-2′,3′-dideoxytubercidin, 9c) were prepared via a free radical β-elimination of bromo and phenoxy(thiocarbonyl) leaving groups from appropriate 5′-O-(2-acetoxyisobutyryl)-2′(3′)-phenoxy(thiocarbonyl)-3′(2′)-bromo derivatives 6, 7 of adenosine (1a), inosine (1b) and tubercidin (1c) with tributyltin hydride and subsequent deprotection of the resulting 5′-O-(2-acetoxyisobutyryl)-2′,3′-didehydro-2′,3′-dideoxynucleosides 8a, 8b and 8c, respectively.