in tetrahydrofuran T=35°C; 2 h;

toluene-4-sulfonic acid; p-toluenesulfonyl chloride

in toluene 20 h; Reflux;

in diethyl ether

1: triethylamine / acetonitrile / 4 h / 20 °C 2: H2 / Pd / acetic acid; 2-methyl-propan-2-ol; H2O View Scheme

sodium hydrogen telluride in N,N-dimethyl-formamide T=70°C; 3.5 h;

1: EDC; HOBT; N-methylmorpholine / CHCl3 / 0 - 23 °C 2: 99 percent / H2 / 10 percent Pd/C / methanol; ethyl acetate / 2068.59 Torr 3: 82 percent / EDC; HOBT; N-methylmorpholine / CHCl3 / 0 - 23 °C View Scheme

1-hydroxybenzotriazol-hydrate; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; triethylamine in dichloromethane T=20°C;

TEA in N,N-dimethyl-formamide

1: 91 percent / triethylamine, dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBT) H2O / dimethylformamide; CH2Cl2 / 4 h / 0 °C 2: 98 percent / H2 / 5percent PdC / methanol 3: 1.) N-methylmorpholine, isobutyl chloroformate / 1.) THF, -15 - -10 deg, 15 min., 2.) THF, DMF, a) -15 - -10 deg, 2h, b) RT, overnight 4: 86 percent / NaOH / dimethylformamide; acetone / 1 h / Ambient temperature 5: 1.) N-methylmorpholine, isobutyl chloroformate, 2.) N-methylmorpholine / 1.) THF, -15 - -10 deg, 15 min., 2.) THF, DMF, a) -15 - -10 deg, 2h, b) RT, overnight 6: 94 percent / CH2Cl2 / 0.5 h / Ambient temperature View Scheme