A New Method for the Preparation of Acyclonucleosides as a Potential Antiviral Agents

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Reaction of purine nucleosides with diisobutylaluminum hydride (DIBAL-H) in dry tetrahydrofurane resulted in the reductive cleavage of the ribose moiety at the anomeric position to give the corresponding 9-ribitylpurines in good yeilds. Taking into the consideration, the reductive ring opening reaction is likely explained in terms of the initial formation of a Lewis complex : the anomeric position 1' can be activated by the coordination of DIBAL-H with both the furanose ring-oxygen and the 7-ring nitrogen atom, to facilitate the nucleophilic attack of hydride anion at the anomeric position. the selectivity of the reductive cleavage at the anomeric position is obviously governed by virtue of the coordination of aluminum atom with the ring-oxygen.the ring scission analogue of neplanocin A,acycloneplanocin A,as a potential S-adenosylhomocysteine hydrolase inhibitor was synthesized via the reductive cleavage of 2', 3'-O-isopropylideneadenosine by DIBAL-H.The methodology using this reductive cleavage of nucleosides with DIBAL-H was shown to be applicable to the synthesis of biologically important acyclonucleosides.To the best of our knowledge, the present reductive cleavage of the ribose moiety in purine nucleosides with DIBAL-H is unprecedented and is of great interest for the preparation of antiviral cyclonucleosides.