Studies of nucleosides and nucleotides—XLV Purine cyclonucleosides.-12. Synthesis of adenine cyclonucleosides having 8,5′-0-anhydro linkage

A cyclonucleoside having an 8,5′-0-anhydro linkage was first synthesized by treatment of 8-bromo-2′-3′-O-isopropylideneadenosine with sodium hydride in dioxan at room temperature. The cyclonucleoside (III) has UV absorption properties similar to those reported for other 0-cyclonucleosides and shows a large positive Cotton curve in ORD and CD.

When compound III was heated in N H₂SO₄, 8-oxyadenosine (IV) and 8,5′-anhydro-8-oxyadenosine (V) were obtained. Heating III in 0·1N H₂SO₄ gave 5-(adenyl-8)-D-ribose (VI). Treatment of III with sodium hydride in DMF gave a nucleoside having an exocyclic methylene (VII).

Compound III was also reacted with potassium thiocyanate, sodium azide and hydrogen sulfide. In each case the nucleophiles attacked at C⁵′ and gave 5′-substituted 8-oxyadenosine.