The protection of amino acids is very important in peptide synthesis, which directly determines the success of peptide synthesis. Because many of the common 20 amino acids have active side chains, which need to be protected. Generally, these protective groups are stable in the synthesis process, without side reaction, and can be completely removed quantitatively after synthesis.

The amino acids that need to be protected in synthesis include Cys, ASP, Glu, his, Lys, ASN, Gln, Arg, Ser, THR, Trp and Tyr. Groups to be protected: hydroxyl, carboxyl, sulfhydryl, amino, amido, guanidine, indole, imidazole, etc. Trp may not be protected because indole is stable. Of course, in special cases, some amino acids may not be protected, such as Asn, Gln, Thr, Tyr.

Here are 20 Fmoc amino acids commonly used in peptide synthesis:

Fmoc-Lys(Boc)-OH

Fmoc-Met-OH

Fmoc-Ala-OH

Fmoc-Arg(Pbf)-OH

Fmoc-Asn(Trt)-OH

Fmoc-Asp(OtBu)-OH

Fmoc-Cys(Trt)-OH

Fmoc-Gln(Trt)-OH

Fmoc-Glu(OtBu)-OH

Fmoc-Gly-OH

Fmoc-L-His(Trt)-OH

Fmoc-Ile-OH

Fmoc-Leu-OH

Fmoc-Ser(tBu)-OH

Fmoc-Phe-OH

Fmoc-Pro-OH

Fmoc-Thr(tBu)-OH

Fmoc-Trp(Boc)-OH

Fmoc-Tyr(tBu)-OH

Fmoc-Val-OH