Cyclic dinucleotide covalent modifier and preparation method and application thereof

The invention relates to a cyclic dinucleotide covalent modifier as well as a preparation method and application thereof. The invention particularly relates to a method for linking a linking arm to acompound shown in a formula SF. According to the method, the linking arm is linked to S in phosphorus sulfonyl of the compound shown in the formula SF, and thus, by the method for linking the linkingarm to the compound shown in the formula SF, influence on the activity of the compound shown in the formula SF is very small, and linkage of the linking arm to the S in the phosphorus sulfonyl can beused in the aspects of covalent linkage of a target unit such as a synthesis combined adjuvant, macromolecule covalent loading, fluorescence labeling and the like. Therefore, as a novel STING agonist,the compound shown in the formula SF is used as a STING passagemechanism research probe, an immunotherapy reagent and animmunologic adjuvant for treating immune-related diseases, and for example, canbe used for treating tumors,