CS(C)=O.C(Cl)(=O)C(Cl)=O.[OH:11][C@H:12]1[C@H:17]([C:18]2[C:23]([O:24][CH3:25])=[CH:22][C:21]([O:26][CH3:27])=[CH:20][C:19]=2[O:28][CH3:29])[CH2:16][CH2:15][N:14]([CH3:30])[CH2:13]1.C(=O)([O-])[O-].[Na+].[Na+]>C(Cl)Cl.O.C(N(CC)CC)C>[CH3:30][N:14]1[CH2:15][CH2:16][CH:17]([C:18]2[C:23]([O:24][CH3:25])=[CH:22][C:21]([O:26][CH3:27])=[CH:20][C:19]=2[O:28][CH3:29])[C:12](=[O:11])[CH2:13]1Dimethyl sulfoxide (35 ml) is added dropwise under nitrogen to a solution, cooled to -60° C., of oxalyl chloride (20 ml) in dry methylene chloride (500 ml), and the mixture is stirred for 5-10 minutes. A solution of (±)-trans-3-hydroxy-4-(2,4,6-trimethoxyphenyl)-1-methylpiperidine (62 g) in methylene chloride (300 ml) is then added, while the temperature of the reaction mixture is held at -60° C. After the addition, the mixture is stirred for 15 minutes and triethylamine (155 ml) is added. The reaction mixture is then allowed to warm to a temperature of -30° C., diluted with water and rendered alkaline with sodium carbonate. The organic layer is separated off and the aqueous layer is extracted with ethyl acetate. The organic layers are combined, washed with brine, dried over anhydrous Na2SO4 and concentrated to give a solid residue which, on crystallization from isopropanol, gives the desired product (47 g) of melting point 110°-112° C.
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