Ribosylation of the Base Residue of Inosine Derivatives by Phase-Transfer Catalysis

Abstract

Reaction of 2′,3′,5′-O-silylated inosine derivative 1 with 2, 3-O-isopropylidene-5-O-tritylribosyl chloride (3) in a two-phase (CH₂Cl₂-aq. NaOH) system in the presence of Bu₄NBr gave three products, i. e., 6-O-α-, 6-O-β-, and N ¹-β-isomers of glycosides 4, 5a, and 5b. A similar PTC reaction of 1 with 2, 3, 5-tri-O-benzylribosyl bromide (9) gave four regio- and stereo-isomers involving the N¹-β-glycoside 10. Reaction of 1 with 2, 3, 5-tri-O-benzoylribosyl bromide (11) afforded three products involving the desired N¹-β-glycoside 12b, which could be deprotected to give N ¹-ribosylinosine (15b) as a useful intermediate for the synthesis of cIDPR.