Structure-Selectivity Relationship of a Peptide Catalyst

Significance

A detailed study on the mode of action of catalyst 1 employed in asymmetric epoxidations is presented. The observed, nearly retained enantiomeric excess achieved with analogue 2 suggests that the NHBoc group is not involved in a key H-bonding interaction with the substrate. On the other hand, replacement of the amide function with an alkene 4 or a fluoroalkene 3 group leads to a significant drop in enantiomeric excess. Mechanistic insights in their mode of action are provided by the structure-dependent catalytic behavior of these isosteric peptides.