Introduction of Peptide Synthesis Reagents

Peptide synthesis reagent is the reagent used to connect carboxyl group and amino group to form amide bond, mainly condensation reagent. According to the molecular structure of synthetic reagents, they can be roughly divided into carbodiimide type, phosphorus positive ion type, urea positive ion type, imine positive ion type, organic phosphorus condensation agent and others. Among them, carbodiimide type, urea positive ion type and phosphorus positive ion type are the three main types of agents. Carbodiimide type is the earliest and most commonly used peptide condensation agent. Urea positive ion and phosphorus positive ion type condensation agents have the best performance, while urea positive ion condensation agents show more excellent performance in peptide synthesis. They have become the mainstream peptide condensation agents used in scientific research and are the most widely used.

Generations of Peptide Synthesis Reagents

The emergence of peptide synthesis reagents is a great breakthrough in amide bond synthesis. Peptide synthesis reagents have developed to the fourth generation. The first generation of peptide synthesis reagents are carbodiimide condensation agents represented by dicyclohexyl carbodiimide (DCC), N, N-diisopropyl carbodiimide (DIC) and 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC). However, the condensation efficiency of these reagents is not high and they are easy to produce serious racemization. The second generation of peptide synthesis reagents are based on the emergence of 1-hydroxybenzotriazole (HOBt), 1-hydroxy-7-azabenzotriazole (HOAt) and other additives. They can effectively inhibit racemization and improve the reaction rate when used in combination with carbodiimide condensation agent and ionic condensation agent; However, HOBt and HOAt are inflammable and explosive, which makes transportation and treatment more troublesome. The third generation of peptide synthesis reagents are onium salt condensates derived from HOBt and HOAt (represented by phosphorus positive ion condensates and urea positive ion condensates). These reagents enable unnatural amino acids and sterically hindered amino acids to be successfully applied to peptide synthesis. Their performance is superior to other types of condensates in terms of reaction activity, product yield and purity. The fourth generation of peptide synthesis reagents are new additives and condensation agents derived from oxymatrine.  Oxymatrine and its derivatives have the advantages of cheap and easy raw materials, simple synthesis method, good solubility, stable properties, simple treatment, low toxicity of by-products, and some can even be recycled and reused.

Applications of Peptide Synthesis Reagents

Peptide synthesis reagents can not only be used as condensing agents, such as in the condensation of CO₂ and halogenated hydrogen to produce urethane. There are other broad applications. Peptide synthesis reagents can be used as important pharmaceutical and pesticide intermediates. They are used to manufacture pharmaceutical anesthetics, pesticides, herbicides and so on. Meanwhile, they can be used as catalysts. For example, they are used as the catalysts for ester hydrolysis under high pressure. They can be used as catalysts in the hydrolysis or condensation of phenylchloroformic acid. In addition, peptide synthesis reagents can also be used as catalysts for the arylation of dihydrofuran in the presence of trifluorobenzene.