benzotriazol-1-ol; triethylamine; dicyclohexyl-carbodiimide in N,N-dimethyl-formamide 1.) ice bath, 1 h, 2.) 23 deg C, 15 h;

benzotriazol-1-ol; triethylamine; dicyclohexyl-carbodiimide 1.) DMF, 23 deg C, 0.5 h, 2.) DMF a.) 0 deg C, 2 h, b.) 23 deg C, 15 h; Yield given. Multistep reaction;

1.1: NMM; isobutyl chloroformate / acetonitrile / 0.17 h / -15 °C 1.2: 1-hydroxybenzotriazole hydrate / acetonitrile / 0.17 h / cooling 1.3: 90.5 percent / NMM / acetonitrile; dimethylformamide / 20 °C / pH 8 2.1: HCl / dioxane / 1.5 h 3.1: 89.6 percent / NMM; isobutyl chloroformate / dimethylformamide; acetonitrile 4.1: HCl / dioxane / 1.5 h 5.1: 90.1 percent / NMM; isobutyl chloroformate / acetonitrile 6.1: ammonium formate / palladium on carbon / methanol / 0.5 h / 20 °C 7.1: trifluoroacetic acid View Scheme

1: tetrahydrofuran / 0.25 h / -20 °C 2: tetrahydrofuran / 1.) -20 deg C, 10 min, 2.) RT, 1 h 3: HCl / ethyl acetate / 3 h View Scheme

1: mixed anhydride method 2: mixed anhydride method 3: mixed anhydride method 4: H2 / catalytic hydrogenolysis View Scheme

trifluoroacetic acid

1: tetrahydrofuran / 0.25 h / -20 °C 2: tetrahydrofuran / 1.) -20 deg C, 10 min, 2.) RT, 1 h 3: HCl / ethyl acetate / 3 h 4: Et3N / CH2Cl2 / 4 h 5: H2 / Pd black / ethanol; acetic acid / 30 h / Ambient temperature 6: 1 N aq. NaOH / ethanol / 30 h / Ambient temperature View Scheme