[CH3:1][NH:2][C:3]([C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=1)([CH2:6][CH3:7])[CH2:4][OH:5].[Li]CCCC.[CH3:19][O:20][C:21]1[CH:22]=[C:23]([CH:27]=[C:28]([O:32][CH3:33])[C:29]=1[O:30][CH3:31])[C:24](Cl)=[O:25].C(O)(=O)C>C1COCC1>[CH3:7][CH2:6][C:3]([NH:2][CH3:1])([C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][CH:9]=1)[CH2:4][O:5][C:24]([C:23]1[CH:27]=[C:28]([O:32][CH3:33])[C:29]([O:30][CH3:31])=[C:21]([O:20][CH3:19])[CH:22]=1)=[O:25]To a solution of 1.84 g of 8 (10.3 mmol) in 28 mL of anhydrous THF were added dropwise, at −78° C., 4.11 mL of n-BuLi (2.5 mol/L in hexanes). After 15 minutes, a solution of 2.31 g (10.01 mmol) of 3,4,5-trimethoxybenzoyl chloride in 15.8 mL of anhydrous THF was added. The reaction mixture was then allowed to warm to −30° C. (ca 1 h) and 19 mL of acetic acid were cautiously added. Solvents were removed under vacuum and 55 mL of diethyl ether and 55 mL of water were added to the previously obtained oil. After stirring until complete dissolution, the resulting mixture was then decanted and the aqueous layer alcalinized completely with solid Na2CO3 and re-extracted with diethyl ether. The organic layers were washed twice with a saturated aqueous solution of sodium carbonate and with brine and then dried over sodium sulphate. Diethyl ether was evaporated under vacuum and the ester 9 was purified by chromatography on silica gel column (ethyl acetate/n-hexane, 7:3) to give 1.4 g of pure N-desmethyltrimebutine 9 (49% yield) as a yellow pale oil. MS(ESI), m/e 374.1 (M+).
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