Acetate → (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetate

Participants

Reaction Conditions

Reaction Steps

To the crude (21.837 g) (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid (41.41% w/w; 9.043 g, 19.77 mmol) containing the (S)-isomer as the ester impurity in a 200 mL round bottom flask was added IPA (150.72 mL). The mixture was heated at 60° C. under N2 till the oily residue dissolved completely. The resultant orange solution was heated at about 60° C. for 5 min. Seeds of L-arginine salt of (R)-2-(7-(4-cyclopentyl-3-trifluoromethyl)benzyloxy)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetate (362 mg) were added. The seeds were suspended in the orange solution. A 2.27 M aqueous solution of L-arginine (8.709 mL, 3.44 g, 19.77 mmol) pre-warmed to about 60° C. was added into the mixture dropwise over 30 min. A light yellow precipitate formed gradually during the addition. The suspension was stirred for about an additional 30 min. The temperature of the suspension was allowed to drop at about 0.4° C. per minute to room temperature. The mixture was agitated occasionally at room temperature overnight. The suspension was filtered and the cake was washed with IPA (3×6 mL) and EtOAc (3×15 mL). The filter cake was dried at room temperature under vacuum overnight to give L-arginine salt of (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetate as a white solid (11.631 g, 44.7%): HPLC 99.38 Area %, 99.6% ee. TGA, PXRD, PLM, SEM and DSC indicated the solid as a non-solvated, crystalline compound with an average aggregates size of 18.05 microns and a melting point of 202.69° C.

Provenance & Evidence