[CH2:1]1[C@H:6]2[CH2:7][C:8](=[O:10])[CH2:9][C@H:5]2[CH2:4][C:3](=[O:11])[NH:2]1.[CH:12](O)([OH:14])[CH3:13].C(=O)(O)[O-].[Na+]>C1(C)C=CC=CC=1.C1(C)C=CC(S(O)(=O)=O)=CC=1>[CH2:1]1[C@H:6]2[CH2:7][C:8]3([O:14][CH2:12][CH2:13][O:10]3)[CH2:9][C@H:5]2[CH2:4][C:3](=[O:11])[NH:2]1(cis)-2,4,4a,5,7,7a-hexahydro-1H-cyclopenta[c]pyridine-3,6-dione 14d (1.20 g, 7.80 mmol), ethanediol (1.34 g, 21.50 mmol) and p-toluenesulfonic acid (24 mg, 0.13 mmol) were dissolved in 60 mL of toluene, heated to reflux for 8 hours with stirring, then added dropwise with saturated sodium bicarbonate solution to adjust pH to 7 around and extracted with dichloromethane (50 mL). The aqueous phase was extracted with dichloromethane (50 mL×3). The combined organic phase was washed with saturated sodium chloride solution (50 mL×3), then dried over anhydrous magnesium sulfate, filtered and the filtrate was concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain the title compound (cis)-spiro[1,3-dioxolane-2,6′-2,4,4a,5,7,7a-hexahydro-1H-cyclopenta[c]pyridine]-3′-one 14e (1.10 g, yield: 70.0%) as a white solid.
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