合成路线1

In a related procedure, 1,6-anhydro-L-gulose (IX) was obtained from L-gulose (VIII) by treatment with 0.5 N HCl. Oxidative cleavage of (IX) by NaIO4, followed by reduction of the aldehyde groups with NaBH4, led to the dioxolane triol (X), which was further protected as the isopropylidene ketal (XI). Benzoylation of the free hydroxyl of (XI), followed by acidic hydrolysis of the acetonide group, furnished the benzoate diol (XII). Then, oxidation of the vicinal diol moiety of (XII), by means of RuO2 in the presence of NaIO4, afforded carboxylic acid (III). Oxidative decarboxylation of acid (III) with lead tetraacetate produced the key acetoxy dioxolane (XIII). This was coupled with the silylated N-acetylcytosine (XIV) in the presence of trimethylsilyl triflate to yield a mixture of anomers, which were separated by column chromatography. Final hydrolysis of the desired isomer (VII) was then performed by treatment with methanolic ammonia.