Recent advancements on the synthesis and biological significance of pipecolic acid and its derivatives

Pipecolic acids are cyclic non-protein amino acids serving as precursors for the biosynthesis of biological metabolites. Structurally, the six-membered cyclic motif consists of five-carbons and one nitrogen atom. The pipecolic acid (Pip) nucleus is present as a central structural component in many biological systems. It is a cyclic amino acid derived from L-lysine which has gained interest in the recent years within the pharmaceutical and chemical industries. This review focuses on three aspects of Pip. The first part provides detailed introduction and synthesis of Pip, while the second part describes the incorporation of Pip into peptides and lastly, in the third part, the biological applications of Pip are discussed. Herein, we have presented a detailed review on Pip and combined, for the first time, peptides of Pip and biological activities of Pip and its derivatives in one frame.