Total synthesis of (-)-tuberostemonine

Area of Science:

• Organic Chemistry
• Natural Product Synthesis
• Medicinal Chemistry

Background:

• Stemona alkaloids are a class of natural products with potential biological activities.
• Tuberostemonine is a complex pentacyclic Stemona alkaloid.
• Total synthesis provides access to complex natural products for further study.

Purpose of the Study:

• To achieve the first total synthesis of the complex pentacyclic Stemona alkaloid, tuberostemonine.
• To develop an innovative synthetic strategy that efficiently utilizes stereochemical information from a readily available precursor.

Main Methods:

• A 24-step synthetic route was designed starting from Cbz-l-tyrosine.
• Key steps included ruthenium-catalyzed azepine ring-closing metathesis, alkene isomerization, and cross-metathesis.
• Stereoselective attachment of the gamma-butyrolactone moiety was achieved using a lithiated ortho ester.

Main Results:

• The first total synthesis of tuberostemonine was successfully accomplished.
• An overall yield of 1.4% was obtained from a hydroindole intermediate.
• The synthetic strategy effectively relayed the stereocenter of the amino acid precursor to nine stereocenters in the target molecule.

Conclusions:

• The developed synthetic route represents a significant advancement in the synthesis of complex Stemona alkaloids.
• The methodology highlights the utility of ruthenium catalysis and stereoselective functionalization in complex molecule construction.
• This synthesis provides a foundation for exploring the biological properties and potential applications of tuberostemonine.