dicyclohexyl-carbodiimide in ethyl acetate T=0 - 20°C; 1 h;

1: N-(9-fluorenylmethoxycarbonyl)-L-aspartic acid-β-(tert-butyl)ester With 4-methyl-morpholine; N-methyl-N-(4,6-dimethoxy-2,4,6-triazin-2-yl)-morpholinium p-toluenosulphonate in acetonitrile T=0°C; 2 h; 2: 2,3,4,5,6-pentafluorophenol in acetonitrile T=0 - 20°C; 20 h;

pyridine in N,N-dimethyl-formamide 0.75 h; Ambient temperature;

1: 78 percent / NaHCO3 / H2O; acetone / Ambient temperature 2: dicyclohexylcarbodiimide / ethyl acetate / 2 h / 0 °C View Scheme

1: 78 percent / NaHCO3 / H2O; acetone / Ambient temperature 2: dicyclohexylcarbodiimide / ethyl acetate / 2 h / 0 °C View Scheme

Multistep reaction;

sodium tetrahydroborate in tetrahydrofuran T=20°C; 0.5 h;