Total Synthesis of Crotophorbolone

Area of Science:

• Organic Chemistry
• Natural Product Synthesis
• Diterpenoid Chemistry

Background:

• Crotophorbolone is a complex tigliane diterpenoid with a unique ABC-tricyclic structure.
• Tigliane diterpenoids are known for their diverse biological activities, making their synthesis a significant challenge.
• Previous synthetic efforts have not achieved the total synthesis of crotophorbolone.

Purpose of the Study:

• To achieve the first total synthesis of crotophorbolone.
• To develop a stereoselective and efficient synthetic route to this complex natural product.
• To explore novel synthetic methodologies for constructing congested polycyclic systems.

Main Methods:

• Stereoselective construction of a six-membered C-ring fragment from (R)-carvone.
• π-Allyl Stille coupling for A-ring attachment.
• α-Alkoxy bridgehead radical reaction for endo-cyclization of the B-ring.
• Rhodium-catalyzed C2 olefin isomerization, C13 decarboxylative oxidation, and C4 hydroxylation for functional group manipulation.

Main Results:

• Successful assembly of the complex ABC-tricyclic core of crotophorbolone.
• Stereoselective formation of five contiguous stereocenters in the C-ring.
• Stereospecific and stereoselective formation of the sterically hindered C9-C10 bond.
• Completion of the total synthesis through strategic functional group interconversions.

Conclusions:

• The first total synthesis of crotophorbolone has been accomplished.
• The developed synthetic strategy provides a viable route to complex tigliane diterpenoids.
• This work demonstrates the power of radical cyclization and transition-metal catalysis in natural product synthesis.