The greening of protection/deprotection strategies in peptide synthesis.

The presence of functional groups in a wide range of biologically active compounds makes their protection and deprotection an important and frequently mandatory exercise in synthetic organic chemistry.1 In particular, protection and deprotection of the -amino functionality of amino acids is one of the most important issues in peptide synthesis. Therefore, introduction as well as removal must be done in mild conditions that do not affect the remaining protecting groups or even the peptide chain.2 Although there are hundreds of protective groups that can be introduced and removed by a variety of methods, new and milder strategies continue to be developed for many of the existing protective groups; nevertheless, most of them have their own particular drawbacks. The selection of mild reaction conditions for the use of protective groups is a crucial seek of the contemporary synthetic chemistry. The use of ionic liquids (ILs) and deep eutectic solvents (DES) in organic synthesis has received great attention due to their unusual properties as nonconventional solvents.3 Recently, we explored the applicability of these green solvents as reaction media, for the selective introduction and removal of various protecting groups4-6 and for the synthesis of potential biologically active compounds.