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温度

0 °C

Compound 2a (1 g, 1.48 mmol) was dissolved in 1,2-dichloroethane (2 l). The mixture was degassed for 15 min using a stream of argon. Hoveyda-Grubbs catalyst (II) (50 mg, 5 mol %) was added and the mixture was refluxed for 4 h. The solvent was evaporated and the crude ester was dissolved in THF (100 ml), methanol (50 ml) and water (50 ml). The mixture was cooled to 0° C. on an ice-bath. Aqueous lithium hydroxide (20 ml, 1M) was added and the mixture was stirred at 0° C. for 4 h. The volume was then doubled by addition of water and the mixture was acidified with acetic acid. Extraction (dichloromethane) followed by flash column chromatography (methanol 1→5% in ether) gave pure title compound (450 mg, 61%).

1. customThe mixture was degassed for 15 min
2. additionHoveyda-Grubbs catalyst (II) (50 mg, 5 mol %) was added
3. temperaturethe mixture was refluxed for 4 h
4. customThe solvent was evaporated
5. dissolutionthe crude ester was dissolved in THF (100 ml)
6. additionAqueous lithium hydroxide (20 ml, 1M) was added
7. additionThe volume was then doubled by addition of water
8. extractionExtraction (dichloromethane)