Condensing agent

The condensing agent refers to a reaction auxiliary agent added in the condensation reaction. There are generally catalyzed condensing agents and condensing agents which, when condensed, combine with the resulting separated atoms or groups of atoms. The former is, for example, an acid catalyst in an esterification reaction, aluminum trichloride in a Friedl-Crafts reaction, and the like; the latter is a sodium metal or the like in a Wurtz-Fittig reaction. Two or more organic compound molecules emit a simple molecule such as water, ammonia, or hydrogen chloride to form a larger molecule, which is called a condensation reaction. Sometimes two organic compound molecules interact to form a larger molecule without releasing a simple molecule, also called a condensation (reaction), such as an aldol condensation. The choice of condensing agent depends on the type of condensation reaction, the structure of the reactants, the reaction conditions and the materials removed during the reaction. Protecting groups and condensing agents in chemical synthesis: In the chemical synthesis of nucleic acids, both nucleosides and mononucleotides as raw material monomers are polyfunctional compounds. When they are chemically linked, the group that removes the desired reaction will react, and other groups will participate in the reaction, resulting in various by-products such as self-polymerization, misconnection, and degradation. This not only reduces the yield of the desired synthesis product, but also makes it difficult to separate and purify the product. In order to ensure that the synthetic product can have the same 3'-5' phosphodiester bond structure and nucleotide arrangement order as the natural nucleic acid, this requires a high degree of orientation and specificity of the synthesis reaction. The solution is to temporarily protect the groups that do not require a reaction in the ligation reaction (such as a hydroxyl group on a sugar, an amino group on a base, a hydroxyl group on a phosphate, etc.) with a suitable protecting group as much as possible. Therefore, the choice of the protection base has a great relationship with the success of the synthesis. The choice of condensing agent is also important. The main reaction in nucleic acid synthesis is that phosphoric acid reacts with the hydroxy group of ribose or deoxyribose to form a phosphate bond. At present, a high activity and low side reaction condensing agent is firstly reacted with a phosphate component to form activated phosphoric acid, and then condensed with a hydroxyl component.