合成路线1

L-Gulono-gamma-lactone (I) was reduced with DIBAL and then protected as the diisopropylidene ketal (III). This was converted to 1,6-anhydrogulopyranose (IV) upon treatment with 0.5N HCl. Subsequent oxidative cleavage of (IV) with NaIO4, followed by reduction with NaBH4 provided triol (V), which was protected as the isopropylidene derivative (VI) with acetone and TsOH. Condensation of (VI) with benzoyl chloride in the presence of pyridine yielded benzoate ester (VII). Then, ketal deprotection of (VII) afforded diol (VIII). Oxidative treatment with NaIO4/RuO2 produced acid (IX), and further oxidative decarboxylation with Pb(OAc)4 furnished dioxolanyl acetate (X). 5-Iodouracil (XI) was silylated using hexamethyldisilazane and a catalytic amount of (NH4)2SO4. The resulting silylated uracil (XII) was coupled with dioxolanyl acetate (X) in the presence of trimethylsilyl triflate to afford an anomeric mixture of nucleosides (XIII). Title compound was then obtained by deprotection of the benzoate ester of the mixture (XIII) with methanolic ammonia, followed by chromatographic isolation of the desired L-anomer.