1: 1,1-dimethylethyl 1,4-dioxo-8-azaspiro[4.5]-8-carboxylate With N,N,N',N,-tetramethylethylenediamine; sec.-butyllithium in diethyl ether T=-78 - -70°C; 5.5 h; 2: methyl iodide in diethyl ether T=-78 - 20°C;

1: With trifluoroacetic acid T=0 - 5°C; 0.166667 h; 2: With water 2.5 h; Heating / reflux;

toluene-4-sulfonic acid in acetone T=0 - 20°C;

hydrogenchloride in ethyl acetate T=20°C; 5 h;