Vidarabine synthesis method

The invention relates to a vidarabine synthesis method. The method comprises the steps that 8-hydroxy-N,3',5'-O-triethyl-2'-O-p-tosyl adenosine is added, hydrazine hydrate with the mass time being 1.1-1.4 and the mass percent being 80% is added, heating is conducted to reach 78-85 DEG C, and a thermal reaction is conducted for 45-50 h; distillation is conducted under pressure reduction, and the hydrazine hydrate is removed; the original raw materials of water with the mass time being 5-8 and catalytic oxidizer potassium permanganate with the mass time being 0.03-0.12 are added, a stirring reaction is conducted at the room temperature for 6-8 h, a solid obtained after reaction liquid is filtered is a vidarabine crude product; the crude product is subjected to actived carbon decoloration andrecrystallization in sequence, and a vidarabine pure product is obtained. Accordingly, a cascade reaction is conducted through a one-pot two-step method, overturning and deprotection of configurationare completed through a h