C([C@H]1COC(=O)N1[C:14](=[O:25])[CH:15]([C:19]1[CH:24]=[CH:23][CH:22]=[CH:21][CH:20]=1)[CH2:16][CH:17]=[CH2:18])C1C=CC=CC=1.[O:26]1CCCC1.O.[OH-].[Li+].OO>O>[C:19]1([C@H:15]([CH2:16][CH:17]=[CH2:18])[C:14]([OH:25])=[O:26])[CH:20]=[CH:21][CH:22]=[CH:23][CH:24]=1Combine (S)-4-benzyl-3-(2-phenylpent-4-enoyl)-2-oxazolidinone (3.35 g, 10 mol), tetrahydrofuran (80 mL), and water (20 mL). Cool in an ice bath. Add lithium hydroxide hydrate (0.84 g, 20 mmol) and an aqueous solution of hydrogen peroxide (4 mL, 30%, 46.4 mmol). After 3 hours, concentrate the reaction mixture to about half volume, dilute the concentrated reaction mixture with an aqueous 1 M sodium hydroxide solution and extract twice with diethyl ether. Cool the aqueous layer in an ice bath, acidify with an aqueous 3 M hydrochloric acid solution, and extract twice with dichloromethane. Extract the combined organic layers with a saturated aqueous sodium thiosulfate solution, dry over MgSO4, filter, and evaporate in vacuo to give (S)-2-phenylpent-4-enoic acid: Rf =0.48 (silica gel, 5% methanol/dichloromethane).
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