BRANCHED-CHAIN SUGAR NUCLEOSIDES .I. 9-[3-DEOXY-3-C-(2'-HYDROXYETHYL)-BETA-D-ALLOFURANOSYL]ADENINE AND 9-[3-DEOXY-3-C-(2'-HYDROXYETHYL)-BETA-D-RIBOFURANOSYL]ADENINE

The synthesis of two novel branched-chain sugar nucleosides is described. The key intermediate in this synthesis, 3-deoxy-3-C-(2′-hydroxyethyl)-1,2:5,6-di-O-isopropylidene-α-D-allofuranose (3), was prepared by application of a Wittig reaction to 1,2:5,6-di-O-isopropylidene-α-D-ribo-hexofuran-3-ulose (1). Compound 3 was hydrolyzed selectively to the 1,2-monoisopropylidene derivative 4, which was converted via benzoylation and acetolysis into 1,2-diacetate 6. Condensation of this compound with 6-benzamidochloromercuripurine in the presence of titanium tetrachloride, followed by deblocking with methanolic sodium methoxide, yielded the branched-chain nucleoside 9-[3-deoxy-3-C-(2′-hydroxyethyl)-β-D-allofuranosyl]adenine (8) in 48% yield based on 6. In a separate procedure, 3-C-(carbomethoxymethyl)-3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-allofuranose (2) was degraded to 3-deoxy-3-C-(2′-hydroxyethyl)-1,2-O-isopropylidene-α-D-ribofuranose (10). The latter was then used in a parallel procedure to that used for the preparation of nucleoside 8 to prepare the branchedchain nucleoside 9-[3-deoxy-3-C-(2′-hydroxyethyl)-β-D-ribofuranosyl]adenine (9) in 37% yield based on the diacetate. The ORD and nmr spectra of the branched-chain sugar nucleosides are described. © 1969, American Chemical Society. All rights reserved.