[CH:1]1([CH:6]([C:14]2[CH:19]=[CH:18][C:17]([F:20])=[CH:16][CH:15]=2)[C:7]([O:9]C(C)(C)C)=[O:8])[CH2:5][CH2:4][CH2:3][CH2:2]1.FC(F)(F)C(O)=O>ClCCl>[CH:1]1([CH:6]([C:14]2[CH:19]=[CH:18][C:17]([F:20])=[CH:16][CH:15]=2)[C:7]([OH:9])=[O:8])[CH2:5][CH2:4][CH2:3][CH2:2]12.20 g (about 88% pure, 6.96 mmol) of (+/−)-tert-butyl cyclopentyl(4-fluorophenyl)acetate were dissolved in 2.9 ml of dichloromethane, and 10.7 ml of trifluoroacetic acid were added at RT. The mixture was stirred at RT for 3 h and then concentrated under reduced pressure. The residue was dried under high vacuum overnight. The solid obtained was triturated with acetonitrile and then filtered off with suction and washed with a little acetonitrile. Drying under high vacuum gave 720 mg of a first solids batch. The filtrate obtained above was concentrated and the residue was purified by preparative RP-HPLC (mobile phase acetonitrile/water). This gave a further 529 mg of the target product (overall yield 80.8% of theory).
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