Treatment of 2,,3'-0-methoxyethylideneadenosine (1) with excess pivalic acid chloride in refluxing pyridine gave a mixture composed primarily of 6-lV-pivalamido-9-(3-chloro-3-deoxy-2-0-acetyI-5-0-pivalyl-d-D-xylofuranosyljpurine (2a) and 6-lV-pivalamido-9-(3-chloro-3-deoxy-5-0-pivalyl-2-0-[4,4-dimethyl-3-pivalyloxypent-2enoy 1]-ß-d-xylofuranosyl)purine (2b) in high combined yield. Methanolic sodium methoxide converted this mixture to 9-(2,3-anhydro-/3-D-ribofuranosyl)adenine (adenosine ribo-epoxide) (3) in greater than 60% overall yield from starting adenosine. The epoxide 3 was found to spontaneously decompose (presumably via the N3-*^'xylo-cyclonucleoside, i) to the ring-opened aminoimidazole carboxamidine cyclonucleoside ii in water. Sodium hydroxide smoothly effected transformation of ii to the corresponding carboxamide, iii. Pivalylation and benzoylation of 3 in pyridine with the appropriate acid chloride gave 6-M-pivalamido-9-(5-0-pivalyl-2,3-anhydroß-o -ribofuranosyl)purine ( 4) and the corresponding N,N, 08,-tribenzoate, 6, respectively. Tetraethylammonium fluoride in refluxing acetonitrile followed by methoxide deblocking converted 4 or 6 into 9-(3-fluoro-3-deoxy-/3-D-xylofuranosyl)adenine ( 7). Reaction of 6 with sodium benzoate in moist DMF followed by deblocking gave 9-/3-d -xylofuranosyladenine (adenine xyloside) (8) in high yield. Treatment of 6 with sodium azide in hot DMF gave 9-(3-azido-3-deoxy-/3-n-xylofuranosyl)adenine (9a) in excellent yield after removal of protecting groups. Hydrogenation of 9a gave 9-(3-amino-3-deoxy-/3 -d -xylofuranosyl) adenine (9b). Treatment of the crude product [presumably a mixture of N-benzoylated 9-(3,5-di-0-benzoyl-/3-D-xylofuranosyl)adenines] from sodium benzoate

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