In solid-phase peptide synthesis, it is required that the raw amino acids participating in the reaction do not participate in the formation of peptide bonds, and the active functional groups are protected. At the same time, after the reaction, the protective groups of these active groups can be removed.

Popular protective amino acids and reagents:

Fmoc-OSu   CBZ-OSu

2,3,5-Trimethylphenol    N-Fmoc-7-methyl-L-tryptophan

Fmoc-Pen(Acm)-OH  Fmoc-Pen(Trt)-OH

The development focus of amino acid protection mainly focuses on: ① NEW α- The development of amino protective groups, NSC, DDE, NDE and other groups have the characteristics of reducing racemization and improving deprotection efficiency; ② For the development of side chain active group protection, a variety of protective groups with excellent stability, high selectivity and reducing side reactions have been developed for different active groups. The protective amino acids prepared in practical applications show excellent properties. With the increasingly complex structure of synthetic peptides, the protective groups of amino acids tend to develop in the direction of selectivity and specificity. With their unique advantages, enzymatic and photolytic protective groups may become a new hotspot in the future.

When selecting amino acid protective groups, the problem of reaction selectivity should be fully considered, that is α- Amino protective groups and α- Carboxyl protective group is a temporary protective group. After an amino acid is bound to the peptide chain, it should be removed immediately; The side chain protective group is a "permanent" protective group, which will not be affected by the reactant during the synthesis of the peptide, and will not react. It will be finally removed after the peptide synthesis. Therefore, the stability of the side chain protective group is greater than α- Amino protective groups and α- Carboxyl protecting group.