Macrocyclic Core of Salarin C: Synthesis and Oxidation

Area of Science:

• Natural Product Synthesis
• Organic Chemistry
• Marine Natural Products

Background:

• Salarin C is a cytotoxic natural product isolated from the sponge Fascaplysinopsis sp.
• The macrocyclic core of salarin C contains two epoxide moieties.
• Salarin A is derived from salarin C through a photooxidation process.

Purpose of the Study:

• To describe the synthesis of the macrocyclic core of salarin C.
• To replace the epoxide moieties with alkene groups.
• To investigate the conformational properties and chemical transformations of the synthesized macrocycle.

Main Methods:

• The synthesis involved key steps such as ring-closing metathesis.
• Alkene moieties were used to replace the original epoxide groups.
• NOESY-based conformational analysis was employed.
• Photooxidation using singlet oxygen mimicked the conversion of salarin C to salarin A.

Main Results:

• The synthesis successfully generated the macrocyclic core of salarin C with alkene replacements.
• Ring-closing metathesis exclusively yielded the (E)-alkene product.
• Conformational analysis revealed a planar arrangement of the oxazole ring and side chains.
• Photooxidation of the oxazole unit afforded macrocyclic trisacylamines.

Conclusions:

• A synthetic route to the salarin C macrocyclic core was established, featuring alkene moieties instead of epoxides.
• The study elucidated the conformational preferences of the macrocycle.
• The research successfully mimicked a key transformation in the salarin C to salarin A conversion, yielding new macrocyclic trisacylamines.