Branched-chain sugar nucleosides. IV. 9-(3-Deoxy-3-C-"hydroxymethyl"-β(and α)-D-allofuranosyl and ribofuranosyl)adenine

Abstract

Hydroboration followed by alkaline hydrogen peroxide oxidation of 1,2:5,6-di-O-isopropylidene-3-C-methylene-α-D-ribo-hexofuranose (2) yielded 3-deoxy-3-C-"hydroxymethyl"-1,2:5,6-di-O-isopropylidene-α-D-allofuranose (3) and partially hydrolyzed 3 in a total yield of 88%. Compound 3 was hydrolyzed selectively to the 1,2-monoisopropylidene derivative 5, which was converted via benzoylation followed by acetolysis into the 1,2-diacetate 7. Condensation of the latter compound with chloromercuri-N-benzoyladenine in the presence of titanium tetrachloride, followed by deblocking with methanolic sodium methoxide, yielded 9-(3-deoxy-3-C-"hydroxymethyl"-β(and α)-D-allofuranosyl)adenine in yields of 44 and 4% respectively, based on 7. The over-all yield of 10 based on 3 is 20%. Sodium metaperiodate oxidation of 10, followed by sodium borohydride reduction of the aldehydo-derivative, afforded 9-(3-deoxy-3-C-"hydroxymethyl"-β-D-ribofuranosyl)adenine (11) in 81% yield.Direct acetolysis of 3, followed by conversion of the mixture of peracetates into a mixture of glycosyl chlorides, and finally condensation of the latter with 8 gave the blocked crystalline β-D-nucleoside 9 in an over-all yield of about 9%, based on 3. Subsequent unblocking of 9 gave a nucleoside having the same physical constants as 10.