Total synthesis of (-)-securingine G.

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Natural Product Synthesis

Background:

• (-)-securingine G is a complex natural product with a challenging molecular structure.
• Existing biosynthetic pathways for related compounds present synthetic hurdles.
• Novel synthetic strategies are needed for efficient access to complex alkaloids.

Purpose of the Study:

• To achieve the first total synthesis of (-)-securingine G.
• To develop a synthetic route that diverges from the proposed biosynthetic pathway.
• To establish a new method for nucleophilic pyridine anion addition in complex molecule synthesis.

Main Methods:

• The synthesis employed a nucleophilic pyridine anion addition strategy.
• A key step involved the use of a tri(2-pyridinyl)lanthanum complex to control reactivity.
• A new reagent, n-Bu3La·5LiCl, was developed for efficient halide/lanthanum exchange.

Main Results:

• Successfully synthesized (-)-securingine G, marking the first total synthesis.
• The developed method circumvented undesired base-mediated side reactions.
• Demonstrated the utility of the novel lanthanum complex and exchange reagent in challenging coupling reactions.

Conclusions:

• The first total synthesis of (-)-securingine G was accomplished.
• The developed synthetic strategy offers a viable alternative to biosynthetic pathways.
• The novel lanthanum-based reagents expand the toolkit for organometallic synthesis and complex molecule construction.