[C:1]1([C:7]([C:18]2[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=2)([C:12]2[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=2)[O:8][CH2:9][CH2:10][OH:11])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.C([Li])CCC.CCCCCC.Br[CH2:36][C:37]([OH:39])=[O:38]>C1COCC1.O>[C:1]1([C:7]([C:18]2[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=2)([C:12]2[CH:13]=[CH:14][CH:15]=[CH:16][CH:17]=2)[O:8][CH2:9][CH2:10][O:11][CH2:36][C:37]([OH:39])=[O:38])[CH:2]=[CH:3][CH:4]=[CH:5][CH:6]=1
2-(Triphenylmethoxy)ethanol (3.98 g, 0.013 mol) was dissolved in dry THF (50 ml) and a 2.5 M solution of butyllithium in hexane (5.5 ml, 0.0137 mol) was added at 0° C. A solution of bromoacetic acid (1.81 g, 13.0 mmol) was separately treated with a 2.5 M solution of butyllithium in hexane (5.5 ml, 13.7 mmol) at 0° C. before the two solutions were mixed. This reaction mixture was heated at reflux for 68 h, cooled, and water (200 ml) was added. Washing with ethyl acetate was followed by acidification of the aqueous phase with 0.5 M citric acid solution (50 ml). Extraction with ethyl acetate (2 × 100 ml) and drying (MgSO4) provided crude [2-(triphenylmethoxy)ethoxy]acetic acid (2.78 g, 58%). This acid was dissolved in dichloromethane (30 ml) and dicyclohexylcarbodiimide (1.72 g, 0.0083 mol) was added, followed by 4-pyrrolidinopyridine (0.11 g, 0.00074 mol) and ethanol (0.89 ml, 2 equiv.) (A. Hassner et al., Tetrahedron Lett. (1978) 4475). The reaction mixture was stirred for 16 h at room temperature and filtered to remove dicyclohexyl urea. The filtrate was evaporated, and the residue was purified by flash chromatography on silica gel (3 × 20 cm). Elution with cyclohexane containing 1-3% ethyl acetate provided the desired [2-(triphenylmethoxy)ethoxy]acetic acid ethyl ester (1.5 g, 50%) as an oil.
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