Weighing 5-fluorocytosine 25.0g in 500ml three-necked bottle, to which added 55ml of toluene, hexamethyldisilamine 2ml, 110 heating reflux 6.5h, after the completion of the reaction, concentrated reaction solution. Then add 26.0g of triacetyl ribose and 200ml of dichloromethane to reduce the temperature to -10~0, add 20ml of tin tetrachloride and 50ml of dichloromethane mixed solution dropwise, react for 8h, adjust the pH with aqueous sodium bicarbonate to 4~5, and then extract with dichloromethane for two times, merge the organic phases, and then obtain the condensate by evaporation and concentration.
Add n-pentyl chloroformate 30 mlg, dichloromethane 100 ml, pyridine 20 ml to the condensate, react at -15 for 2h, adjust pH4-6 with hydrochloric acid, stratify, and concentrate the organic layer to obtain oil.
Add 100ml of acetic anhydride to the oil, heat and reflux for 15h, evaporate the acetic anhydride under reduced pressure, add 450ml of water and 400ml of trichloromethane to extract, 200ml of water washed three times. The trichloromethane layer was concentrated to obtain an oil, which was extracted by dichloromethane and concentrated to obtain an oil.
Finally, it was separated on a silica gel column eluting with ethyl acetate and petroleum ether 1:1, and the final product was collected, concentrated and dried to obtain the white-like compound with high purity.1H-NMR (400MHz, CDCl3)δ0.1.0~1.07 (t, 3h), 1.20(t,3H), 1.29(d,2H), 1.34~1.36(d,4H), 1.57(d,4H), 1.57(d,4H), 1.57(d,4H), 1.57(d,4H), 1.57(d,4H), 1.57(d,4H). ), 1.57 (d,2H), 4.08 (d,2H), 4.55 (d,2H), 4.59~4.60 (s,2H), 5.94 (d,2H), 6.93 (m,1H) 8.0 (s,1H). Liquid phase purity 99% .