Robust Chemical Synthesis of "Difficult Peptides" via 2-Hydroxyphenol-pseudoproline (ψpro) Modifications.

The challenging preparation of "difficult peptides" has always hindered the development of peptide-active pharmaceutical ingredients. Pseudoproline (ψpro) building blocks have been proven effective and powerful tools for the synthesis of "difficult peptides". In this paper, we efficiently prepared a set of novel 2-(oxazolidin-2-yl)phenol compounds as proline surrogates (2-hydroxyphenol-pseudoprolines, ψpro) and applied it in the synthesis of many well-known "difficult peptides", including human thymosin α1, amylin, and β-amyloid (1-42) (Aβ42).