1.1: sodium tetrahydroborate / methanol / 0.67 h / 20 °C 2.1: dichloromethane / 5 h / 20 °C 3.1: acetonitrile / 0.5 h / 20 °C 4.1: lithium trifluoromethane sulfonate / N,N-dimethyl-formamide / 0.5 h / 0 °C / Molecular sieve; Inert atmosphere 4.2: 0 °C / Inert atmosphere 4.3: 0 - 20 °C / Inert atmosphere 5.1: water; acetic acid / acetonitrile / 17 h / 80 °C 5.2: 17 h / 70 °C View Scheme

1: With sodium hydride in tetrahydrofuran T=20 - 40°C; 2.25 h; 2: With hydrogenchloride in tetrahydrofuran; diethyl ether T=20°C; 3 h;

sodium tetrahydroborate in methanol Reduction; 22 h;

1.1: sodium tetrahydroborate / methanol / 0.67 h / 20 °C 2.1: dichloromethane / 5 h / 20 °C 3.1: acetonitrile / 0.5 h / 20 °C 4.1: lithium trifluoromethane sulfonate / N,N-dimethyl-formamide / 0.5 h / 0 °C / Molecular sieve; Inert atmosphere 4.2: 0 °C / Inert atmosphere 4.3: 0 - 20 °C / Inert atmosphere 5.1: water; acetic acid / acetonitrile / 17 h / 80 °C View Scheme

1: With sodium hydride in tetrahydrofuran T=20 - 40°C; 2.25 h; 2: With hydrogenchloride in tetrahydrofuran; diethyl ether T=20°C; 3 h;

N,N,N',N',N'',N''-hexamethylphosphoric triamide; di-n-butylchlorotin hydride in tetrahydrofuran T=0°C; Reduction; 2.5 h;