1. Hydrogen bonding peptides as asymmetric organocatalysts
Brian R. Linton, Department of Chemistry, College of the Holy Cross
Enantioselective organocatalysts have been developed for nitroalkane conjugate addition. These peptide catalysts result from modular solid-phase and solution-phase syntheses, and are able to control the addition of nitroalkanes to vinyl ketones with stereoselectivities up to 74% ee, as shown below. The peptides function as green catalysts, since they are employed at two mole percent, contain no metals, and are easily biodegradable.
The best peptide catalysts (bottom left) present hydrogen bonding amino acid sidechains on the same face of a beta-turn scaffold. Mechanistic investigations suggest the assembly of substrates on one face of the peptide catalyst (below at right). Currently we are optimizing the stereoselectivity by modifying individual amino acid residues, as well as exploring the use of alternate substrates.
peptide catalyst