[C:1]([C:4]12[CH2:11][CH:10]3[CH2:12][C:6]([C:13]([OH:15])=[O:14])([CH2:7][CH:8]1[CH2:9]3)[CH2:5]2)(=[O:3])[CH3:2].[C:16](Cl)(=O)C>CO>[C:1]([C:4]12[CH2:11][CH:10]3[CH2:12][C:6]([C:13]([O:15][CH3:16])=[O:14])([CH2:7][CH:8]1[CH2:9]3)[CH2:5]2)(=[O:3])[CH3:2]To 3-acetyltricyclo[3.3.1.03,7]nonane-1-carboxylic acid (2.4 g, 11.4 mmol) obtained in step I, in MeOH (48 mL) cooled to ice bath temperature, was added acetyl chloride (1.64 mL, 22.8 mmol). The reaction mixture was gradually warmed to room temperature and stirred for 2 h. The volatiles were removed under reduced pressure and the crude product was purified by column chromatography to obtain methyl 3-acetyltricyclo[3.3.1.03,7]nonane-1-carboxylate (2.4 g) in 93% yield as viscous liquid. m/z (M+1) 223. IR cm−1 2953, 1728, 1698, 1461, 1234, 1078, 755. 1H NMR (CDCl3) 300 MHz δ 3.66 (s, 3H), 2.75-2.70 (m, 1H), 2.53-2.46 (m, 1H), 2.40-2.32 (m, 1H), 2.19 (s, 3H), 2.15-2.05 (m, 1H), 2.03-1.60 (m, 8H). 13C NMR (CDCl3) 75 MHz δ 210.9, 175.3, 61.4, 53.4, 51.6, 50.5, 48.0, 45.9, 45.6, 42.6, 41.9, 36.8, 35.9, 26.4.
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