Synthetic method for capecitabine key intermediate

The invention discloses a synthetic method for capecitabine key intermediate 2`,3`-O-diacetylpyridine-5`-deoxygenation-5-fluorine-N4-[(pentyloxy) carbonyl] cytidine. The synthetic method for the capecitabine key intermediate comprises the following steps that 1, 5- fluorocytosine, an acid-binding agent, chloroform, water and phase transfer catalyst are mixed, pentyl chloroformate is added dropwise under stirring, and the chloroform solution of (5-fluorine-2-oxo-1,2-dihydropyrimidine-4-base) amylcarbamate is obtained; 2, 1,2,3-three-O-acetyl-5-deoxygenation-6- ribofuranose is added into the chloroform solution obtained in the step 1, lewis acid is added dropwise, the reaction is performed for 2-10 hours after adding, and the capecitabine key intermediate is obtained after post-processing. The synthetic method is simple and convenient in operation, a silicane protective agent and intermediate product purification are not needed, the high yield of finished products is achieved, the proportion of alpha isomer in the products is effectively controlled, and compared with literature data, the purity of the obtained products is greatly improved.