[NH:1]([C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[C@H:2]([C:10]([OH:12])=[O:11])[CH2:3][C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1.O1CC[CH2:22][CH2:21]1.[C:25]([Li])(C)(C)[CH3:26].[B-](F)(F)(F)F.CC[O+](CC)CC>O>[CH2:21]([O:11][C:10](=[O:12])[C@H:2]([CH2:3][C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1)[N:1]([C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH2:25][CH3:26])[CH3:22]To a mixture of 2.65 g (10 mmole) of Boc-Phe in 50 ml of cold (ca. -78°), dry tetrahydrofuran was added 12 ml (ca. 22 mmole) of 1.9M t-butyllithium. After thirty minutes, the mixture was allowed to warm to -20° and then to react with 4.2 g (22 mmole) of triethyloxonium fluoborate. After thirty minutes, the mixture was allowed to warm to 0° and then poured into water and extracted with dichloromethane. The organic extract was washed sequentially with portions of 5% aqueous sodium bicarbonate and water, dried over sodium sulfate, filtered, and concentrated to dryness. Distillation (ca. 130°-200°) afforded an oil that was further purified by column chromatography on silica gel to give the title compound (4.7 g) as an analytically pure solid, m.p. 58°-61.5°.
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