合成路线1

The reaction of D-glutamic acid (I) with NaNO2 and HCl gives the lactone carboxylic acid (II), which is esterified with EtOH and Ts-OH to yield the ester (III), reduced with NaBH4 in ethanol and silylated with Tbdps-Cl and imidazole to afford the protected chiral lactone (IV). The selenation of lactone (IV) with N-(phenylseleno)phthalimide (V) by means of LiHMDS and Tms-Cl in THF gives a mixture of diastereomers with a higher ratio (3:1) of the desired isomer (VI). (The unwanted isomer (VII) can be isomerized by reaction with DBU in THF.) The reduction of the lactone (VI) with DIBAL in toluene affords the lactol (VIII), which is treated with Ac2O and TEA to provide the acetoxy compound (IX). The condensation of (IX) with 5-fluoro-N,O-bis(trimethylsilyl)cytosine (X) by means of Tms-OTf in dichloromethane gives the selenated cytosine derivative (XI), which is treated with H2O2 in THF/pyridine to yield the unsaturated silylated precursor (XII). Finally, this compound is desilylated with HF and TEA in THF to afford the target cytosine derivative.