Toluene → (2S)-2-[4-[4-(6-carbamoyl-3,5-dimethylpyrazin-2-yl)-2-fluorophenyl]-3-chlorophenyl]propanoic acid

Participants

Reaction Conditions

Reaction Steps

2-[4-[4-(6-Carbamoyl-3,5-dimethylpyrazin-2-yl)-2-fluorophenyl]-3-chlorophenyl]prop-2-enoic acid (Intermediate 31-10; 142 g, 283.44 mmol), bis(1,5-cyclooctadiene)rhodium(I) tetrafluoroborate (1.381 g, 3.40 mmol), (R)-1-[(Sp)-2-(di-tert-butylphosphino)ferrocenyl]ethylbis(2-methylphenyl)phosphine (2.102 g, 3.68 mmol) in degassed methanol (2.5 L) and degassed toluene (836 mL) were stirred under an atmosphere of hydrogen at 5 bar and 45° C. for 4 hours. Chiral HPLC analysis (chiralpak AD 5 μm, 250 mm×4.6 mm column, eluted with 60% isohexane/40% ethanol/0.2% acetic acid, retention time for required enantiomer 14.5 minutes) indicated the ratio of desired to undesired enantiomer was 87:13. The solvent was removed in vacuo. The crude product was dissolved in 5% methanol/dichloromethane and then chromatographed on silica (5 Kg of Merck lichro prep silica 15-25 μm, 200 mm diameter column), eluting with a solvent mixture of 5% methanol/dichloromethane. Pure fractions were evaporated to dryness to afford the mixture of the enantiomers, chiral prep HPLC chromatography (5 Kg of chiralpak AD 20 μm, 200 mm diameter column, eluted with 70% isohexane/30% ethanol/0.2% acetic acid, retention time for required enantiomer 17 minutes) then gave (2S)-2-[4-[4-(6-carbamoyl-3,5-dimethylpyrazin-2-yl)-2-fluorophenyl]-3-chlorophenyl]propanoic acid (58 g, 40%, 99% ee) as a white solid.

Provenance & Evidence