The Total Synthesis of Chalcitrin

Area of Science:

• Organic Chemistry
• Natural Product Synthesis
• Medicinal Chemistry

Background:

• Chalcitrin is a yellow pigment found in the fungus Chalciporous piperatus.
• Its unique pulvinic acid dimer structure presents a synthetic challenge.
• Previous characterization identified it as a free acid, but this study suggests otherwise.

Purpose of the Study:

• To achieve the first total synthesis of chalcitrin.
• To explore efficient synthetic routes for its complex polycyclic core.
• To clarify the exact natural form of chalcitrin.

Main Methods:

• A 17-step linear synthesis from commercially available starting materials.
• Utilized gold(I)-catalyzed Conia ene reaction for core construction.
• Employed N-heterocyclic carbene-mediated acyloin addition for polycyclic core formation.
• Introduced side chains via a late-stage double Stille coupling.

Main Results:

• Successful total synthesis of chalcitrin.
• Demonstrated the efficacy of gold(I) and N-heterocyclic carbene catalysis in constructing the core.
• Identified challenges with alternative synthetic designs due to steric hindrance.
• Revealed that the originally characterized material was the carboxylate salt, not the free acid.

Conclusions:

• The first total synthesis of chalcitrin was accomplished.
• The study highlights the utility of specific catalytic reactions for complex molecule synthesis.
• Corrected the understanding of chalcitrin's natural form, impacting future research and characterization.