[C:1]1([C:7]2[C:8]([C:18]([O:20]C)=[O:19])=[N:9][O:10][C:11]=2[C:12]2[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=2)[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.[Li+].[OH-]>CO.C1COCC1.O>[C:1]1([C:7]2[C:8]([C:18]([OH:20])=[O:19])=[N:9][O:10][C:11]=2[C:12]2[CH:13]=[CH:14][CH:15]=[CH:16][CH:17]=2)[CH:2]=[CH:3][CH:4]=[CH:5][CH:6]=1To a thick suspension of methyl 4,5-diphenylisoxazole-3-carboxylate (306 mg, 1.09 mmol) in MeOH (8 mL), THF (2 mL) and water (2 mL) at rt was added LiOH, hydrate (46.0 mg, 1.09 mmol) and the reaction mixture was allowed to stir at rt for 1 hr. During this time, the reaction became homogeneous. The MeOH and THF were removed in vacuo and the remaining aqueous mixture was acidified to pH ˜1 with 1N HCl. The mixture was then extracted with EtOAc (30 mL). The organic layer was washed with brine (20 mL), dried (MgSO4) and concentrated to afford 4,5-diphenylisoxazole-3-carboxylic acid (290 mg, 1.09 mmol, 100% yield) as a yellow solid. HPLC retention time=1.72 minutes (YMC Combi 4.6×30 mm S-5 ODS column) eluting with 10-90% aqueous methanol+0.1 TFA a 2 minute gradient.
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