S-to-N acyl transfer, intramolecular

Monbaliu JCM, Dive G, Stevens CV, Katritzky AR (2013) Governing parameters of long-range intramolecular S-to-N acyl transfers within (S)-acyl isopeptides. J Chem Theory Comput 9 927-934... 

The governing parameters for the long-range conversion of (5)-acyl isopeptides (41 X = [CHRCOl OH) to native peptide analogues (42 X = [CHRCO]j OH) via intramolecular S-to-N acyl transfer (Scheme 13) are shown by computational and statistical methods (principal component analysis and cluster analysis) of model... 

Thioester ligation involves two segments, each containing a thioester and a Cys that results in the production of a cysteine residue at the ligation site. In this approach, the first step is formation of a covalent thioester-linked intermediate by nucleophilic attack of the thiol side chain of an AT-cysteine peptide on a thioester segment. An intramolecular S — N acyl transfer to form an amide bond then completes the ligation reaction (Figure 6). 

Figures. Thiol-thioester exchange to form an amide bond. Nucleophilic attack takes place by the side chain thiol functionality in a cysteinyl peptide at a thioester segment to form an intramoiecular thioester, which undergoes intramolecular S N acyl transfer to form an amide bond.

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