Incipient Twisted Ribbon Structure Stabilized by C12Helical Turns in γ4/α Hybrid Peptide

Synthesis and migrastatic activity of cytochalasin analogues lacking a macrocyclic moiety

Cytochalasans are known as inhibitors of actin polymerization and for their cytotoxic and migrastatic activity. In this study, we synthesized a series of cytochalasin derivatives that lack a macrocyclic moiety, a structural element traditionally considered essential for their biological activity. We focused on substituting the macrocycle with simple aryl-containing sidechains, and we have also synthesized compounds with different substitution patterns on the cytochalasin core. The cytochalasin analogues were screened for their migrastatic and cytotoxic activity. Compound 24 which shares the substitution pattern with natural cytochalasins B and D exhibited not only significant in vitro migrastatic activity towards BLM cells but also demonstrated inhibition of actin polymerization, with no cytotoxic effect observed at 50 μM concentration. Our results demonstrate that even compounds lacking the macrocyclic moiety can exhibit biological activities, albeit less pronounced than those of natural cytochalasins. However, our findings emphasize the pivotal role of substituting the core structure in switching between migrastatic activity and cytotoxicity. These findings hold significant promise for further development of easily accessible cytochalasan analogues as novel migrastatic agents.

Ambidextrous α,γ-Hybrid Peptide Foldamers

Molecular chirality is ubiquitous in nature. The natural biopolymers, proteins and DNA, preferred a right-handed helical bias due to the inherent stereochemistry of the monomer building blocks. Here, we are reporting a rare co-existence of left- and right-handed helical conformations and helix-terminating property at the C-terminus within a single molecule of α,γ-hybrid peptide foldamers composed of achiral Aib (α-aminoisobutyric acid) and 3,3-dimethyl-substituted γ-amino acid (Adb; 4-amino-3,3-dimethylbutanoic acid). At the molecular level, the left- and right-handed helical screw sense of α,γ-hybrid peptides are representing a macroscopic tendril perversion. The pronounced helix-terminating behaviour of C-terminal Adb residues was further explored to design helix-Schellman loop mimetics and to study their conformations in solution and single crystals. The stereochemical constraints of dialkyl substitutions on γ-amino acids showed a marked impact on the folding behaviour of α,γ-hybrid peptides.