Protected nucleosides are mainly used in the synthesis of nucleic acids and their derivatives in chemical and biological research. The role of protecting groups is to prevent the active groups of nucleosides (such as hydroxyl, amino, etc.) from undergoing undesirable reactions in chemical reactions, thereby improving the selectivity and yield of the synthesis. They are often used in nucleic acid synthesis, such as the synthesis of DNA or RNA, to ensure that specific reaction steps do not damage the structure of the synthesized part.