1: (1S)-(+)-N-(2,2-dimethylpropionyl)-1-phenylethylamine With n-butyllithium; tert.-butyl lithium in tetrahydrofuran; hexane; pentane T=-78 - -60°C; 2: carbonic acid diethyl ester in tetrahydrofuran; hexane; pentane T=-78 - 20°C; Further stages.;