Synthesis of (-)-aphanorphine using aryl radical cyclization

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Medicinal Chemistry

Background:

• (-)-aphanorphine is a complex alkaloid with potential pharmacological applications.
• Efficient synthetic routes are crucial for accessing such molecules for further study.
• Radical cyclization offers a powerful strategy for constructing complex ring systems.

Purpose of the Study:

• To develop a novel and efficient synthetic route to (-)-aphanorphine.
• To explore the utility of tin hydride-mediated aryl radical cyclization in alkaloid synthesis.
• To achieve exclusive formation of the 6-exo cyclization product.

Main Methods:

• The synthesis employed a 1-benzyloxycarbonyl-2-(2-bromo-4-methoxyphenylmethyl)-2-methoxycarbonyl-4-(phenylthiomethylene)pyrrolidine precursor.
• Tributyltin hydride (Bu(3)SnH) was used to mediate an aryl radical cyclization reaction.
• Reaction conditions were optimized to favor the desired cyclization pathway.

Main Results:

• The aryl radical cyclization proceeded efficiently, yielding the target molecule.
• Exclusive formation of the 6-exo cyclization product was observed.
• The synthetic strategy proved effective for constructing the core structure of (-)-aphanorphine.

Conclusions:

• Tin hydride-mediated aryl radical cyclization is a viable and selective method for synthesizing (-)-aphanorphine.
• This approach provides a valuable tool for the synthesis of related alkaloids and complex organic molecules.
• The study highlights the power of radical chemistry in modern organic synthesis.