Hydrochloric Acid → (S)-Suprofen

Participants

Reaction Conditions

Reaction Steps

To 100 mg crude Candida cylindracea lipase (Sigma L1754 Type VII, 500 units/mg solid) in 4 mL 0.2 M phosphate buffer, pH 7.0, was added 200 mg (±)-α-methyl-4-(2-thienylcarbonyl)benzeneacetic acid methyl ester (suprofen methyl ester). The resulting suspension was gently stirred with a magnetic stirrer for 48 hours at 22° C. The reaction mixture was acidified to pH 1.0 with 1 N HCl and exhaustively extracted with ethyl acetate three times. The combined organic extract was dried over sodium sulfate and was then evaporated to dryness. The residue was chromatographed over a silica gel (MN Kieselgel 60) column (0.8×15 cm). Elution of the column with a solvent system consisting of ethyl acetate-hexane (1:5) gave unreacted (R)-α-methyl-4-(2-thienylcarbonyl)benzeneacetic acid methyl ester, [α]D25 =-54.7° (c=3.9, CHCl3), ee>0.90, and (S)-α-methyl-4-(2-thienylcarbonyl)benzeneacetic acid, [α]D25 =+43.5° (c=2.1, CHCl3), ee>0.95. The optical purity expressed as enantiomeric excess (ee) is determined by proton magnetic resonance spectroscopy of the methyl ester in the presence of the chiral lanthanide shift reagent, Eu(hfc)3.

Provenance & Evidence