Cl.[CH2:2]([O:4][C:5]([C:7]1[N:11]=[C:10]([CH:12]([NH:24][CH3:25])[CH2:13][C:14]2[CH:23]=[CH:22][C:21]3[C:16](=[CH:17][CH:18]=[CH:19][CH:20]=3)[CH:15]=2)[O:9][N:8]=1)=[O:6])[CH3:3].Cl.[CH3:27]C(O)C>CC([O-])C.CC([O-])C.CC([O-])C.CC([O-])C.[Ti+4]>[CH3:3][CH:2]([O:4][C:5]([C:7]1[N:11]=[C:10]([CH:12]([NH:24][CH3:25])[CH2:13][C:14]2[CH:23]=[CH:22][C:21]3[C:16](=[CH:17][CH:18]=[CH:19][CH:20]=3)[CH:15]=2)[O:9][N:8]=1)=[O:6])[CH3:27]5-(1-methylamino-2-(2-naphthyl)ethyl)-[1,2,4]oxadiazole-3-carboxylic acid ethyl ester hydrochloride (1.64 g, 4.5 mmol) was suspended in 2-propanol (35 ml). After addition of tetraisopropyl titanate (1.3 g, 4.5 mmol) the reaction mixture was refluxed for 18 h. Hydrochloric acid (1N, 30 ml) was added and the reaction mixture was extracted with ethyl acetate (150 ml). The organic phase was washed with a saturated aqueous solution of sodium hydrogencarbonate (50 ml) and water (3×50 ml). After drying (magnesium sulfate) the solution was concentrated in vacuo to give 1.3 g of (R) 5-(1-methylamino-2-(2-naphthyl)ethyl)-[1,2,4]oxadiazole-3-carboxylic acid (2-propyl)ester that was used for the next step without further purification.
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