ARABINONUCLEOSIDES

The α‐D‐arabinonucleosides of cytosine (6) and 5‐fluorouracil (9) were prepared from the 2,3,‐5‐tri‐O‐benzoyl‐D‐arabinofuranosyl halides, in keeping with the trans rule. The 2′‐O‐methyl‐)3‐D‐arabinonucleosides of 5‐fluorouraeil (β‐14) and adenine (β‐21a) were prepared from 3,5‐di‐O‐(4‐ehlorobenzoyl)‐2‐O‐methyl‐α‐D‐arabinofuranosyl chloride, although in both cases a lesser amount of the α‐anomer was also found. Reaction of 3,5‐di‐O‐(4‐chlorobenzoyl)‐2‐deoxy‐2‐(methylthio)‐α‐D‐arabinofuranosyl chloride, prepared in four steps from methyl 2,3‐anhydro‐α‐D‐ribofurano‐side (15), with N‐benzoyladenine gave slightly more of the β‐ than the α‐arabinonucleoside 20b. The β‐anomer was converted to 9‐[2‐deoxy‐2‐(methylthio)‐β‐D‐arabinofuranosyl]adenine. Only 1‐α‐D‐arabinofuranosylcytosine (6) proved to be cytotoxic. Copyright © 1979 Journal of Heterocyclic Chemistry