Synthesis of Etrasimod (APD334): Al₂O₃-Promoted Decarboxylative Rearrangements of Cyclopentenones with Stereochemical...

Area of Science:

• Organic Chemistry
• Medicinal Chemistry
• Synthetic Chemistry

Background:

• Etrasimod is an important immunomodulator with therapeutic applications.
• Efficient and scalable synthesis routes are critical for pharmaceutical development.
• Existing synthetic methods may present challenges in terms of yield, stereoselectivity, or scalability.

Purpose of the Study:

• To develop an efficient and stereoselective synthesis pathway for etrasimod.
• To identify key intermediates and optimize reaction conditions for large-scale production.
• To establish a robust route for the synthesis of cyclopenta[b]indol-3-ylacetic acid.

Main Methods:

• Stereoselective synthesis starting from (+)-cis-4-acetoxy-2-cyclopenten-1-ol.
• Al2O3-promoted decarboxylative rearrangement of an alcohol/isocyanate adduct to form (4R)-anilinocyclopent-2-enone.
• One-pot acylation-Michael addition followed by keto α-arylation to construct a tetracyclic fused lactam.
• Subsequent functional group transformations including methanolysis, indoline oxidation, and hydrolysis.

Main Results:

• An overall yield of 5.6% for etrasimod was achieved.
• High enantiomeric excess (98%) was maintained throughout the synthesis.
• A key intermediate, (4R)-anilinocyclopent-2-enone, was efficiently synthesized via a configuration-inverting rearrangement.
• The synthesis culminated in the formation of cyclopenta[b]indol-3-ylacetic acid.

Conclusions:

• The presented pathway offers an efficient and stereoselective route to etrasimod.
• The developed methodology is suitable for the scalable synthesis of this important pharmaceutical compound.
• This work provides a valuable contribution to the field of synthetic organic and medicinal chemistry.