Absolute configuration of (-)-5-benzoyl-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylic acid, the active enantiomer of ketorolac

Abstract
The (-)-S isomer of 5-benzoyl-1,2-dihydro-3H-pyrrolo[1,2-alpha]pyrrole-1-carboxylic acid is about 60 times more potent than the (+)-R isomer in the carrageenan edema test and ca. 230 times more active than the (+)-R isomer in the mouse phenylquinone writhing assay.