[C:1]([O:5][CH2:6][CH3:7])(=[O:4])[CH2:2][OH:3].[S:8](Cl)([C:11]1[CH:17]=[CH:16][C:14]([CH3:15])=[CH:13][CH:12]=1)(=[O:10])=[O:9].C(N(CC)CC)C.O>C(OCC)C>[S:8]([O:3][CH2:2][C:1]([O:5][CH2:6][CH3:7])=[O:4])([C:11]1[CH:17]=[CH:16][C:14]([CH3:15])=[CH:13][CH:12]=1)(=[O:10])=[O:9]A solution of ethyl glycolate (500 mg, 4.8 mmol) and tosyl chloride (915 mg, 4.8 mmol) in anhydrous diethyl ether (2 ml) at 0° C. was treated dropwise with triethylamine (1.34 ml, 9.6 mmol). The temperature was maintained at 0° C. with stirring for a further 2 h. After this time, water was added and the phases separated. The aqueous phase was extracted with fresh diethyl ether. The combined organic extracts were dried (MgSO4), filtered and the solvent removed in vacuo. The crude product was purified by column chromatography over silica gel (Rf=0.29, 25% ethyl acetate in hexane) affording the tosylate 2 as a colorless oil which solidified on standing as a white solid (868 mg, 70%). [This procedure was repeated on 2× scale (1.8 g, 73%)]. δH (400 MHz, CDCl3) 1.22-1.27 (3H, m, CH3), 2.46 (3H, s, ArCH3), 4.16-4.22 (2H, m, CH2CH3), 4.58-4.59 (2H, m, OCH2), 7.36 (2H, d, J=8.2 Hz, ArH), 7.84 (2H, d, J=8.2 Hz, ArH); δc (100.6 MHz, CDCl3) 14.2, 21.9, 62.1, 64.9, 128.3, 130.1, 132.9, 145.5, 166.2; MS (ES+) 276.0 (100%, [M+H2O]+) (ion not detected in ES−).
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