Acetonitrile → 5-Azaspiro[2.4]heptan-4-one, 7-amino-7-methyl-

To an acetonitrile solution (70 mL) of the crude product (800 mg, 3.46 mmol) of 1-(1,2-diamino-1-methylethyl)-1-cyclopropanecarboxylate dihydrochloride was added 1,1,1,3,3,3-hexamethyldisilazane (7.38 mL, 34.6 mmol), and the mixture was heated under reflux under a nitrogen atmosphere in an oil bath at 100° C. for 4 hours. Then the solution was cooled to room temperature, and to the solution was added methanol (70 mL). After that, the solvent was removed under reduced pressure. Thus a crude product of 7-amino-7-methyl-5-azaspiro[2.4]heptan-4-one was obtained as a light brown gum-like solid.