1: With sodium hydroxide; ethanol; water 39 h; 2: With hydrogenchloride; water in ethanol pH=1;

1: azetidine-1,3,3-tricarboxylic acid 1-tert-butyl ester 3-ethyl ester With diphenyl phosphoryl azide; triethylamine in toluene T=80°C; 4 h; 2: tert-butyl alcohol in toluene 4 h;