Abstract: | The preparation of N1 (2,3-O-isopropylidene-β-D-ribofuranosyl)-4-quinazolone ( 6 ) and N3-β-D-ribofuranosyI-4-quinazolone ( 3b ) are reported. The N3 derivative was prepared by the direct condensation of 4-trimethylsilyloxyquinazoline ( 2 ) and 2,3,5-tri-O-benzoyl- D - ribofuranosyl bromide. The N1 derivative was prepared from the previously reported N1 -β-D-ribofuranosyl-2,4-quinazolinedione via the cyclonucleoside 4 . |