ARABINONUCLEOTIDES .I. A STUDY OF FORMATION OF 3'-ARABINONUCLEOTIDYL ESTERS BY CONVERSION OF AN INTERNUCLEOTIDE LINKAGE

A novel reaction of ribooligonucleotides involves the conversion of the ribose moiety of the pyrimidine nucleotides into derivatives of β-D-arabinose without breaking the 3′-5′-internucleotide bonds. The reaction consists of three steps: (1) an activation which generates 2′:3′→5′-cyclic triesters, (2) a thermal rearrangement which produces 3 ′-5′-linked diesters containing O2:2′-cyclonucleosides, and (3) mild alkaline hydrolysis leading to the formation of arabinooligonucleotides. This rather complex process has now been extensively studied on the simplest model, a suitably protected 2′(3′)→-5′-linked diuridine monophosphate. The cyclic triester intermediate, 5′-O-acetyluridylyl-[(2′: 3′)→5 ′]-(2′: 3′-O-isopropylidene)uridine, was also obtained by a de novo synthesis by the general method of Michelson (1959). The formation of 5′-O-acetyl-02:2′-cyclouridylyl-(3′→5′)-(2′:3′-O-isopropylidene)uridine was found to depend on the nature and concentration of the activating agent, the solvent, the temperature, and is base-catalyzed. This step could be at least partially reversed by anhydrous acid. The irreversible alkaline hydrolysis, followed by acidic deblocking, gave arauridylyl-(3′→5′)-uridine in virtually quantitative yield. These results provide useful information with regard to the synthesis and chemistry of polyarabinonucleotides. © 1969, American Chemical Society. All rights reserved.