Electrophilic Triterpenoid Enones: A Comparative Thiol-Trapping and Bioactivity Study

Area of Science:

• Medicinal Chemistry
• Organic Chemistry
• Biochemistry

Background:

• Bardoxolone methyl belongs to the triterpenoid cyanoacrylate class, known for transient covalent binding to thiols.
• The mechanism of this "pulsed reactivity" and its biological effects remain largely unknown.

Purpose of the Study:

• To investigate the reactivity and bioactivity of novel Δ1-dehydrooleanolates.
• To elucidate the structure-activity relationships governing thiol binding and biological modulation by triterpenoid thia-Michael acceptors.

Main Methods:

• Synthesis of a series of Δ1-dehydrooleanolates from oleanolic acid.
• Comparative analysis of thiol reactivity and bioactivity against transcription factors (Nrf2, NF-κB, STAT3).

Main Results:

• The triterpenoid scaffold sterically hinders enone reactivity.
• Electron-withdrawing groups like cyanide or carboxylate restore Michael reactivity transiently.
• Observed a significant dissociation between thiol-trapping and biological endpoint modulation.

Conclusions:

• Steric and electronic factors of the triterpenoid scaffold critically influence reactivity with thiols.
• Shape complementarity plays a key role in the bioactivity of these compounds.
• The study highlights the nuanced interaction between triterpenoid structure, reactivity, and biological function.