Helical peptides are chiral, and can be used as chiral catalysts. We have designed helical peptide foldamers having alpha,alpha-disubstituted alpha-amino acids, and reported the helical-peptide foldamers-catalyzed 1,4-addition reactions of nitroalkane or dialkyl malonate to alpha,beta-unsaturated ketones. In general, small chiral organocatalysts with an amino group catalyzed enantioselective 1,4-addition reactions of dialkyl malonates to cycloalk-2-enones, however, such an organocatalyst could not apply to various ring size of cycloalk-2-enones. Here we demonstrate that the helical peptide can catalyze enantioselective 1,4-addition reactions of dialkyl malonate to cyclic alpha,beta-unsaturated ketones with various ring sizes. We optimized peptide catalysts and reaction conditions to accomplish highly enantioselective reactions. Using an optimized peptide catalyst, the 1,4-addition reactions of dialkyl malonates to cycloalk-2-enones proceeded with excellent enantioselectivities (&gt;94% ee). The helical structure of peptide was revealed by the X-ray crystallographic analysis, and the reaction mechanism was proposed. Furthermore, we developed a peptide-based chiral phosphine ligand for Ag-catalyzed asymmetric [3+2] cycloaddition reaction. These results will be presented in the poster.

Design of helical peptide foldamers for asymmetric reactions

2019 Fall National Meeting

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