Trends to Acid-Labile Cys Protecting Groups: Thp as an Efficient and Non-Aromatic Cys Protecting Group for Fmoc Chemistry

Abstract

Since the discovery of solid-phase peptide synthesis (SPPS) by Merrifield [1], the peptide field has suffered a dramatic change in a wide set of points such as the development of new solid supports, the discovery of highly efficient coupling reagents and additives, as well as the fashionable design of linkers and protecting groups. Consequently, the solid phase peptides synthesis is considered the most efficient way to synthesize a broad number of complex molecules. Into the complete process of the SPPS, a large number of problematic side reactions occur, in consequence during the past decades tremendous efforts have been done in order to avoid this drawbacks that jeopardize the efficiency of this methodology. Amino acid racemization is still an issue in SPPS because of the similarity between the desired product and the concomitant racemic product. In this sense, several factors such as the coupling reagents, the handles or the protecting groups, or even the basic conditions used during the peptide synthesis, could affect directly the integrity of the α-proton, which are able to modulate the amino acid racemization.