Governing Parameters of Long-Range Intramolecular S-to-N Acyl Transfers within (S)-Acyl Isopeptides

The governing parameters for the long-range intramolecular S-to-N acyl transfer in (S)-acyl isopeptides are shown by computational and statistical methods (principal component analysis and cluster analysis) to be driven by enthalpic and geometric effects over the range n = 5-20. The results emphasize the dependency of ΔG(‡) on the geometrical parameters governing the approach of the reactive termini and the importance of stabilizing intramolecular hydrogen bonds in the transition states (TSs), rather than the effects of TS ring-size. The competition between the intra- (uni-) and inter- (bi)molecular acyl transfers were studied for representative examples.