[OH:1][C:2]1[CH:10]=[CH:9][C:8]([OH:11])=[CH:7][C:3]=1[C:4]([OH:6])=[O:5].CS(O[CH2:17][C@@H:18]([CH3:21])[CH2:19][CH3:20])(=O)=O.C([O-])(O)=O.[Na+]>CN(C=O)C>[OH:1][C:2]1[CH:10]=[CH:9][C:8]([OH:11])=[CH:7][C:3]=1[C:4]([O:6][CH2:17][C@@H:18]([CH3:21])[CH2:19][CH3:20])=[O:5]To a solution of 2,5-dihydroxybenzoic acid (15.4 g) in DMF (50 ml) DBU (15.3 ml) was drop wise added. After complete addition (10 min) stirring was continued for 30 min at room temperature, then a solution of (2S)-2-methylbutyl methanesulfonate (16.4 g) in DMF (20 ml) was added drop wise. After complete addition (30 min) the reaction mixture was heated to 80° C. for 6 h. It was then cooled to room temperature, poured into saturated solution of NaHCO3 (200 ml) and extracted with ethyl acetate (2×300 ml). The combined extracts were dried over Na2SO4 and evaporated to dryness. The obtained dark oily residue was purified over silica gel column to give nearly pure (2S)-2-methylbutyl 2,5-dihydroxybenzoate as beige oil.
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