In this review, we have presented the different chemical structures of proteinogenic amino acids. Also, we performed a precise reference scan of the proton balance of amino acids. It is worth noting that, the two most important parts in this review are the principles of chemical peptide synthesis in solution and the protection of the amino acid side group, so we focused the reference survey on them, and we reached many old and new references in these two important parts in the field of peptide synthesis. On the other hand, we also performed an important reference survey of peptide-coupling methodologies. Finally, in this review we presented an important part, the use of peptide coupling reagents, in this part; we focused on the most important and most popular methods used in peptide chemistry reactions.