dicyclohexyl-carbodiimide in N,N-dimethyl-formamide 1.) 0 deg C, 3 h, 2.) room temp., 18 h;

1: 82 percent / trifluoroacetic acid / 10 h / Ambient temperature 2: 60 percent / dicyclohexylcarbodiimide / dimethylformamide / 1.) 0 deg C, 3 h, 2.) room temp., 18 h View Scheme