HALO SUGAR NUCLEOSIDES .6. SYNTHESIS OF SOME 5'-DEOXY-5'-IODO AND 4',5'-UNSATURATED PURINE NUCLEOSIDES

Reactions of the 5''-hydroxyl groups of suitably substituted purine nucleosides with methyltriphenoxyphosphonium iodide in nonpolar solvents such as tetrahydrofuran and dichloromethane give the corresponding 5''-deoxy-5''-iodo nucleosides in high yield. Previously, N3,5''-cyclonucleosides were the major products of these reactions when DMF [dimethylformamide] was used as solvent. Efficient syntheses of 9-(5-deoxy-.beta.-D-erythro-pent-4-enofuranosyl) purine nucleosides are described via dehydrohalogenation of various 5''-deoxy-5''-iodoinosine, -guanosine, and -adenosine derivatives with either silver fluoride in pyridine or 1,5-diazabicyclo[4.3.0]non-5-ene in DMF or pyridine.