Cl[CH2:2][C@H:3]([C@H:5]1[CH2:14][CH2:13][C:12]2[C:7](=[CH:8][CH:9]=[C:10]([F:15])[CH:11]=2)[O:6]1)[OH:4].[OH-].[Na+]>CC(O)C.C1(C)C=CC=CC=1.O>[F:15][C:10]1[CH:11]=[C:12]2[C:7](=[CH:8][CH:9]=1)[O:6][C@@H:5]([C@H:3]1[CH2:2][O:4]1)[CH2:14][CH2:13]2The compound (S*)-2-chloro-1-((R*)-6-fluoro-3,4-dihydro-2H-chromen-2-yl)-ethanol obtained in Example 2 (200 mg, 0.867 mmoles) is dissolved in i-PrOH (1.6 g) under nitrogen and the reaction mixture is cooled to 0° C. On the magnetically stirred mixture is added a 2M aqueous solution of sodium hydroxide (0.9 ml) in 10 min. The mixture is stirred for 1 hour at 0° C., then diluted with toluene (5 ml) and transferred in a separator funnel. The biphasic mixture is further diluted with toluene (5 ml) and demi water (5 ml) and the phases are separated. The organic phase is washed with demi water (10 ml) and concentrated under vacuum to yield (R*)-6-fluoro-3,4-dihydro((R*)-oxiran-2-yl)-2H-chromen as yellow oil (110 mg, 87%, 95% de via GC).
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