Br[CH2:2][CH:3]([O:7][CH2:8][CH3:9])[O:4][CH2:5][CH3:6].[OH:10][C:11]1[C:20]([CH3:21])=[CH:19][C:14]([C:15]([O:17][CH3:18])=[O:16])=[C:13]([CH3:22])[CH:12]=1.C(=O)([O-])[O-].[Cs+].[Cs+]>CN(C=O)C>[CH2:5]([O:4][CH:3]([O:7][CH2:8][CH3:9])[CH2:2][O:10][C:11]1[C:20]([CH3:21])=[CH:19][C:14]([C:15]([O:17][CH3:18])=[O:16])=[C:13]([CH3:22])[CH:12]=1)[CH3:6]2-Bromo-1,1-diethoxyethane (0.31 mL) was added to a mixture of methyl 4-hydroxy-2,5-dimethylbenzoate (example 18, step b) (0.25 g) and caesium carbonate (0.68 g) in DMF (20 mL). The resulting mixture was stirred at 85° C. for 16 h. The reaction was partitioned between water (200 mL) and ethyl acetate (100 mL). The aqueous phase was separated and extracted with ethyl acetate (2×100 mL). The combined organic solutions were washed with water (2×100 mL) and brine (100 mL), dried over magnesium sulphate, filtered and evaporated. The residue was purified by silica gel chromatography eluting with isohexane to 10:1 isohexane:ethyl acetate gradient. The fractions containing product were combined and evaporated in vacuo to give the subtitled compound as a clear oil. Yield 0.26 g.
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