Insight into peptide bond formation from 3D-structural chemistry

This chapter is an update of our contribution on the same topic published 20 years ago which dealt with the important issue of our still incomplete understanding of the reaction mechanisms involved in peptide bond formation and their implications for reactivity, regiospecificity, and propensity to racemize (or epimerize). The electronic and steric properties of five classes of C-carboxyl reactive derivatives of alpha-amino acid and peptides, namely fluorides, anhydrides, esters, azides, and amides are reviewed on the basis of the available 3D-structure information, mainly extracted from detailed X-ray diffraction analyses.