The invention discloses a preparation method of
flucytosine. The preparation method comprises the following steps of S1, material preparation: separately preparing 2-12 parts of organic alkali, 1-10 parts of
cytosine, 2-8 parts of a halogenating
reagent, 0.5-5 parts of an amino protective agent, 1-5 parts of a fluorinating
reagent, 2-9 parts of
aztreonam and 0.5-6 parts of compound probiotics; and S2, preparation I: putting a certain amount of organic alkali into a reaction kettle at the temperature of 80 DEG C, then taking a certain amount of
cytosine and a certain amount of halogenating
reagent, putting the taken
cytosine and halogenating reagent into the reaction kettle, and mixing and stirring with the organic alkali to obtain an intermediate I. According to the
flucytosine preparation method, the preparation steps are simple, unnecessary tedious steps are omitted, the
raw material cost is low, the product quality is very stable, the
treatment effect can be improved and is more remarkable through the added
aztreonam, the nutritional ingredients can be increased through the added compound probiotics, and the side effects can be reduced.