Method for synthesizing 7-denitrification-7-halogen guanosine

The invention discloses a method for synthesizing 7-denitrification-7-halogen guanosine. The method comprises the following steps: removing a protecting group of a compound of the formula (III) under an alkali condition so as to obtain a compound of the formula (IV1) or (IV2) as shown in the specification, wherein R1 is H or OH; R2 is I, Br or Cl; R3 is H or a formula as shown in the specification. The 7-denitrification-7-halogen guanosine synthesized by using the method is a basic raw material with wide application in biology fields such as DNA (Deoxyribonucleic Acid) sequencing, marking and extension, the compound is high in price, complex in synthesis method and hard to control at present, however the method disclosed by the invention is simple and easy to obtain the expected raw materials, the synthesis process is ordinary chemical reaction, and the method can be applied to large-scale popularization and application.