1: tert-butyl 4-oxo-piperidine-1-carboxylate With n-butyllithium; diisopropylamine in tetrahydrofuran; hexane T=-78 - -10°C; 0.25 h; 2: bromoacetic acid tert-butyl ester With tris-(dimethylamino)-phosphine in tetrahydrofuran; hexane T=-78 - 20°C; 4 h; 3: With water; ammonium chloride in tetrahydrofuran; hexane