[CH3:1][O:2][C:3]1[CH:4]=[C:5]([OH:12])[C:6](=[CH:10][CH:11]=1)[C:7]([OH:9])=[O:8].[C:13](=O)(O)[O-].[Na+].S(OC)(OC)(=O)=O>CC(C)=O.CCOCC.C1(C)C=CC=CC=1>[CH3:13][O:8][C:7](=[O:9])[C:6]1[C:5](=[CH:4][C:3]([O:2][CH3:1])=[CH:11][CH:10]=1)[OH:12]
A mixture of 4-methoxysalicylic acid (Aldrich) (178.1 g, 1.06 mmole) sodium bicarbonate (89 g, 1.06 mole), and dimethyl sulfate (133.6 g, 1.06 mole) in acetone (2 l) is refluxed with stirring under nitrogen for 20 hours. The mixture is cooled, filtered, and the acetone is removed under reduced pressure to yield an oily residue. The residue is taken up in ether (1.8 l) and toluene (0.50 l). The extracts are washed with sodium bicarbonate solution, water, dried over sodium sulfate, and concentrated to give a syrup (190.9 g). Recrystallization from hexane gives 172.7 g (89.5%) of analytically pure solid, mp 49°-50° C.
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