[O:1]=[C:2]1[C:11]2[C:6](=[CH:7][CH:8]=[CH:9][CH:10]=2)[CH2:5][C@@H:4]([C:12]([O:14][CH3:15])=[O:13])[CH2:3]1.[CH2:16](O)[CH2:17][OH:18].C1(C)C=CC(S(O)(=O)=O)=CC=1>C1C=CC=CC=1>[C:2]12([O:18][CH2:17][CH2:16][O:1]1)[C:11]1[C:6](=[CH:7][CH:8]=[CH:9][CH:10]=1)[CH2:5][C@@H:4]([C:12]([O:14][CH3:15])=[O:13])[CH2:3]2To a stirred solution of (R)-methyl 4-oxo-1,2,3,4-tetrahydronaphthalene-2-carboxylate (4.5 g, 22.03 mmol) in benzene (40 mL), ethane-1,2-diol (3.69 mL, 66.1 mmol) and a catalytic amount of p-toluenesulfonic acid was added. The reaction mixture was heated to reflux temperature and further maintained for 20 hours. Then, reaction mixture was allowed to RT, concentrated under vacuum to yield 12 g of crude compound. This crude material was purified by flash chromatography (Biotage) using 7% ethyl acetate in hexane to give title compound (4.7 g) m/z 248.6.
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