反应详情

Dissolve (R)-2-hydroxy-4-phenylbutyric acid, ethyl ester (4.16 g, 20 mmol) in methanol (40 mL). Add 1N lithium hydroxide (25 mL, 25 mmol) and stir under an atmosphere of argon for 3.5 hours. Acidify with 1N hydrochloric acid (25 mL), saturate with sodium chloride and extract with ethyl acetate (3×25 mL). Combine the organic phases, dry (MgSO4) and evaporate the solvent in vacuo. Take up the residue in methylene chloride (20 mL) and add diphenyldiazomethane (3.36 g, 17.3 mmol). Stir overnight and wash with saturated sodium hydrogen carbonate (2×). Dry (MgSO4), evaporate the solvent in vacuo and recrystallize (methylene chloride/hexane then again with cyclohexane) to give (R)-2-hydroxy-4-phenylbutyric acid, diphenylmethyl ester as white needles (2.3 g, 38%); mp 82°-84° C.

1. concentrationsaturate with sodium chloride
2. extractionextract with ethyl acetate (3×25 mL)
3. dry with materialCombine the organic phases, dry (MgSO4)
4. customevaporate the solvent in vacuo
5. stirringStir overnight
6. washwash with saturated sodium hydrogen carbonate (2×)
7. dry with materialDry (MgSO4)
8. customevaporate the solvent in vacuo
9. customrecrystallize (methylene chloride/hexane