Peptides – Molecular Allrounders

The enormous structural and functional diversity available through combining different amino acids into peptides offers numerous exciting opportunities. This article summarizes recent research highlights from my laboratory in the areas of asymmetric catalysis, supramolecular chemistry, and chemical biology. This scope includes the development of bioinspired peptide catalysts, synthetic collagen peptides, supramolecular porous assemblies, and cell-penetrating peptides.

The role of β-hairpin conformation in ester hydrolysis peptide catalysts based on a TrpZip scaffold

Peptide catalysts based on TrpZip scaffolds for the hydrolysis of para-nitrophenylacetate in aqueous media were found to have higher catalytic activity in sequences without β-hairpin character.

Catalysis-Enabled Access to Cryptic Geldanamycin Oxides

Catalytic, selective modifications of natural products can be a fertile platform for unveiling not only new natural product analogs with altered biological activity, but also for revealing new reactivity and selectivity hierarchies for embedded functional groups in complex environments. Motivated by these intersecting aims, we report site and stereoselective oxidation reactions of geldanamycin facilitated by aspartyl-peptide catalysts. Through the isolation and characterization of four new geldanamycin oxides, we discovered a synergistic effect between lead peptide-based catalysts and geldanamycin, resulting in an unexpected reaction pathway. Curiously, it seems unlikely that our discoveries would not have been possible absent the outer sphere interactions intrinsic to both the catalyst and the natural product. The result is a set of new “meta” catalytic reactions that deliver both unknown and previously incompletely characterized geldanamycin analogs. Enabled by the catalytic, site-selective epoxidation of geldanamycin, biological assays were carried out to document the bioactivities of the new compounds.<div><br></div>

Catalysis-Enabled Access to Cryptic Geldanamycin Oxides

Catalytic, selective modifications of natural products can be a fertile platform for unveiling not only new natural product analogs with altered biological activity, but also for revealing new reactivity and selectivity hierarchies for embedded functional groups in complex environments. Motivated by these intersecting aims, we report site and stereoselective oxidation reactions of geldanamycin facilitated by aspartyl-peptide catalysts. Through the isolation and characterization of four new geldanamycin oxides, we discovered a synergistic effect between lead peptide-based catalysts and geldanamycin, resulting in an unexpected reaction pathway. Curiously, it seems unlikely that our discoveries would not have been possible absent the outer sphere interactions intrinsic to both the catalyst and the natural product. The result is a set of new “meta” catalytic reactions that deliver both unknown and previously incompletely characterized geldanamycin analogs. Enabled by the catalytic, site-selective epoxidation of geldanamycin, biological assays were carried out to document the bioactivities of the new compounds.<div><br></div>

Ugi reaction-derived prolyl peptide catalysts grafted on the renewable polymer polyfurfuryl alcohol for applications in heterogeneous enamine catalysis

The multicomponent synthesis of prolyl pseudo-peptide catalysts using the Ugi reaction with furfurylamines or isocyanides is described. The incorporation of such a polymerizable furan handle enabled the subsequent polymerization of the peptide catalyst with furfuryl alcohol, thus rendering polyfurfuryl alcohol-supported catalysts for applications in heterogeneous enamine catalysis. The utilization of the polymer-supported catalysts in both batch and continuous-flow organocatalytic procedures proved moderate catalytic efficacy and enantioselectivity, but excellent diastereoselectivity in the asymmetric Michael addition of n-butanal to β-nitrostyrene that was used as a model reaction. This work supports the potential of multicomponent reactions towards the assembly of catalysts and their simultaneous functionalization for immobilization.

Conformational Dynamics in Asymmetric Catalysis: Is Catalyst Flexibility a Design Element?

Traditionally, highly selective low molecular weight catalysts have been designed to contain rigidifying structural elements. As a result, many proposed stereochemical models rely on steric repulsion for explaining the observed selectivity. Recently, as is the case for enzymatic systems, it has become apparent that some flexibility can be beneficial for imparting selectivity. Dynamic catalysts can reorganize to maximize attractive non-covalent interactions that stabilize the favored diastereomeric transition state, while minimizing repulsive non-covalent interactions for enhanced selectivity. This short review discusses catalyst conformational dynamics and how these effects have proven beneficial for a variety of catalyst classes, including tropos ligands, cinchona alkaloids, hydrogen-bond donating catalysts, and peptides.1 Introduction2 Tropos Ligands3 Cinchona Alkaloids4 Hydrogen-Bond Donating Catalysts5 Peptide Catalysts6 Conclusion

Bio-inspired CO2reduction by a rhenium tricarbonyl bipyridine-based catalyst appended to amino acids and peptidic platforms: incorporating proton relays and hydrogen-bonding functional groups

Herein, we report a new approach to bio-inspired catalyst design. The molecular catalyst employed in these studies is based on the robust and selective Re(bpy)(CO)3Cl-type (bpy = 2,2′-bipyridine) homogeneous catalysts, which have been extensively studied for their ability to reduce CO2electrochemically or photochemically in the presence of a photosensitizer. These catalysts can be highly active photocatalysts in their own right. In this work, the bipyridine ligand was modified with amino acids and synthetic peptides. These results build on earlier findings wherein the bipyridine ligand was functionalized with amide groups to promote dimer formation and CO2reduction by an alternate bimolecular mechanism at lower overpotential (ca.250 mV) than the more commonly observed unimolecular process. The bio-inspired catalysts were designed to allow for the incorporation of proton relays to support reduction of CO2to CO and H2O. The coupling of amino acids tyrosine and phenylalanine led to the formation of two structurally similar Re catalyst/peptide catalysts for comparison of proton transport during catalysis. This article reports the synthesis and characterization of novel catalyst/peptide hybrids by molecular dynamics (MD simulations of structural dynamics), NMR studies of solution phase structures, and electrochemical studies to measure the activities of new bio-inspired catalysts in the reduction of CO2.