Discovery of a Unique Structural Motif in Lanthipeptide Synthetases for Substrate Binding and Interdomain Interactions.

Class III lanthipeptide synthetases catalyze the formation of lanthionine/methyllanthionine and labionin crosslinks. We present here the 2.40 Šresolution structure of the kinase domain of a class III lanthipeptide synthetase CurKC from the biosynthesis of curvopeptin. A unique structural subunit for leader binding, named leader recognition domain (LRD), was identified. The LRD of CurKC is responsible for the recognition of the leader peptide and for mediating interactions between the lyase and kinase domains. LRDs are highly conserved among the kinase domains of class III and class IV lanthipeptide synthetases. The discovery of LRDs provides insight into the substrate recognition and domain organization in multidomain lanthipeptide synthetases.

Macrocyclization of bioactive peptides with internal thiazole motifs via palladium-catalyzed C-H olefination.

Peptides containing thiazole fragments represent a large group of bioactive compounds with potential medicinal applications. However, methods for efficient synthesis of these compounds with structural diversity are limited. Herein, we report a method for modification and macrocyclization of thiazole-containing peptides through palladium-catalyzed δ-C(sp2)-H olefination. In this protocol, the thiazole and neighboring amide bonds act as directing groups, which allows site-specific olefination of phenylalanine, tryptophan and tyrosine residues. This chemistry exhibits broad substrate scope and provides facile access to peptide-peptide conjugates and peptide macrocycles. Our results highlight the potency and applicability of thiazole motifs in promoting Pd-catalyzed functionalization of peptides.

Peptide Macrocyclization Through Palladium-Catalyzed Late-Stage C-H Activation.

Cyclic peptides are an important class of bioactive compounds for the chemical biology and pharmaceutical industry. Chemical synthesis of highly constrained cyclic peptides is often challenging. Here we describe the synthetic strategy of peptide macrocyclization through late-stage palladium-catalyzed C-H activation. These methods utilize endogenous backbone amides in the peptide sequence as directing groups and are efficient in the preparation of small-to-middle size peptide macrocycles.

Late-Stage Macrocyclization of Bioactive Peptides with Internal Oxazole Motifs via Palladium-Catalyzed C-H Olefination.

Oxazole is an important pharmacophore and exists in the backbone of many bioactive peptide natural products and peptidomimetics. Efficient methods for the synthesis and direct functionalization of complex oxazole-containing peptides are in high demand. Herein, we report the late-stage site-selective functionalization of oxazole-containing peptides via palladium-catalyzed δ-C(sp2)-H olefination of phenylalanine, tryptophan, and tyrosine residues. This strategy utilizes oxazole motifs as internal directing groups and provides access to oxazole-containing peptide macrocycles with bioactivities.

Late-Stage Peptide Macrocyclization by Palladium-Catalyzed Site-Selective C-H Olefination of Tryptophan.

Transition-metal-catalyzed C-H activation has shown potential in the functionalization of peptides with expanded structural diversity. Herein, the development of late-stage peptide macrocyclization methods by palladium-catalyzed site-selective C(sp2 )-H olefination of tryptophan residues at the C2 and C4 positions is reported. This strategy utilizes the peptide backbone as endogenous directing groups and provides access to peptide macrocycles with unique Trp-alkene crosslinks.

Backbone-Enabled Directional Peptide Macrocyclization through Late-Stage Palladium-Catalyzed δ-C(sp2 )-H Olefination.

C-H activation methods for peptide macrocyclization have the potential to provide peptidomimetics and cyclic peptides with expanded structural diversity. Now, a highly versatile peptide macrocyclization strategy via late-stage palladium-catalyzed δ-C(sp2 )-H olefination of phenylalanine residues has been developed. This method utilizes peptide backbone amides as internal directing groups and allows facile macrocyclization of peptides in the N-to-C direction. Combined with the previously developed ß-C(sp3 )-H arylation method for peptide macrocyclization in the C-to-N direction, a pair of palladium-catalyzed reactions were obtained that are directionally orthogonal, and the first example of one-pot synthesis of bicyclic peptides via Pd-catalyzed ß-C(sp3 )-H and δ-C(sp2 )-H activation is demonstrated.