CHIN-HUNG LAI2026-10-162026-10-162024-09-06Pure ID: 14933933Pure UUID: fedcb57c-5870-4ffb-8fa1-dee4cc37a97f10.1021/acs.joc.4c01463https://www.scopus.com/pages/publications/105001594849https://scholars.csmu.edu.tw/handle/123456789/28303This study presents an efficient synthesis pathway for etrasimod, starting from (+)-cis-4-acetoxy-2-cyclopenten-1-ol, yielding 5.6% overall with 98% enantiomeric excess. The crucial intermediate, (4R)-anilinocyclopent-2-enone, was derived from the (S)-alcohol/isocyanate adduct through a concerted, Al2O3-promoted decarboxylative rearrangement, which inverted the configuration. A tetracyclic fused lactam was formed via a one-pot acylation-Michael addition, followed by keto α-arylation. Subsequent removal of the oxo group facilitated the synthesis of cyclopenta[b]indol-3-ylacetic acid through a series of reactions, including methanolysis, indoline oxidation, and hydrolysis.9enjournal article