The synthesis of peptides is a process of repeated addition of amino acids, and the sequence of solid phase synthesis is usually from the C end (Suo Jiduan) to the N terminal (amino terminal). The past is a polypeptide synthesis in solution called liquid phase synthesis method, and now the use of solid phase synthesis method, which greatly reduces the difficulty of purification of each product. In order to prevent the occurrence of side reactions, the side chains of the amino acids involved in the reaction are protected, while the carboxyl groups are free and must be activated before the reaction. There are two chemical synthesis methods, namely Fmoc and tBoc. Because Fmoc has many advantages over tBoc, most of them are synthesized by Fmoc method

Each cycle consists of the following three steps, which are repeated until the peptide extends to the desired length.

1 deprotection: Fmoc protected amino acids must be protected with an alkaline solvent (piperidine) to remove the amino group.

2 activation: the carboxyl groups of the amino acids to be activated.

3 coupling: activation of the carboxyl and amino acid before a naked amino reaction, the formation of peptide bonds. In this step, the excess reagent is used to promote the reaction.