[OH:1][C:2]1([C:9]#[N:10])[CH2:7][CH2:6][N:5]([CH3:8])[CH2:4][CH2:3]1.S(=O)(=O)(O)[OH:12].C(=O)([O-])[O-].[Ba+2].S([O-])([O-])(=O)=O.[Ba+2]>C(O)C.O>[OH:1][C:2]1([C:9](=[O:12])[NH2:10])[CH2:7][CH2:6][N:5]([CH3:8])[CH2:4][CH2:3]1The compound 4-hydroxy-4-cyano-1-methylpiperidine (36.4 g, 0.26 mole) was gradually added to sulfuric acid (80 ml), under external cooling. The mixture was maintained at room temperature for 41 hours, then was added to powdered ice (30 g). The resulting solution was neutralized with barium carbonate (376 g) to pH 8-9 and after addition of water the resulting barium sulfate was separated and washed with methanol. The filtrate was concentrated under reduced pressure. The product, 4-hydroxy-4 -carbamoyl-1-methylpiperidine (28.16 g, 0.18 mole, 69% yield), crystallized from ethanol as a white solid (mp. 180° C.).
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