To a stirred solution of 2-(4-methoxy-benzenesulfonyl)-3-phenyl-propionic acid ethyl ester (1.0 gm, 3mmol) (example 9), methyl iodide (1 ml, excess) and 18-Crown-6 (500 mg) in acetone (250 ml), K2CO3 (10 gm, excess) was added and the reaction mixture was refluxed for 24 hours. At the end, the reaction mixture was filtered and the acetone layer was concentrated. The residue obtained was extracted with chloroform, washed well with water, dried over anhydrous MgSO4, filtered and concentrated. The product obtained was purified by silica-gel column chromatography by eluting it with 30% ethyl acetate:hexanes to afford 2-(4-methoxy-benzenesulfonyl)-2-methyl-3-phenyl-propionic acid ethyl ester as a colorless oil. Yield 1.0 g, 98%; MS: 349 (M+H)+.
