1: 55 percent / 1,2-dimethoxy-ethane / 1 h / Heating 2: 75 percent / 15percent H2SO4 / 6 h / Heating View Scheme

1: dioxane / 1 h / Heating 2: 74 percent / DMF / 4 h / Heating 3: 96 percent / N2O3 / acetic acid / 1 h / 15 °C 4: 55 percent / 1,2-dimethoxy-ethane / 1 h / Heating 5: 75 percent / 15percent H2SO4 / 6 h / Heating View Scheme

hydrogen; acetic acid; sodium nitrite 1.) H2O, THF, 22 h, 15 - 50 deg C, 2.) MeOH, H2O, RT, 5 h; Yield given. Multistep reaction;

1.1: hydrogenchloride; water / 2 h / 5 °C / |Inert atmosphere; |Large scale 1.2: 1.5 h / 30 °C / pH 12 - 12.5 / |Inert atmosphere; |Large scale 1.3: 2 h / 60 °C / |Inert atmosphere; |Large scale 2.1: LiOH*H2O; water / 20 h / 135 °C / |Autoclave; |Inert atmosphere 3.1: lithium carbonate / methanol; butan-1-ol / 0.17 h / |Reflux 3.2: 2.75 h / 17 - 30 °C / |Reflux 4.1: acetic acid; LiOH*H2O; water; Acylase I / methanol / 0.75 h / 25 - 35 °C / pH 5 - 7.6 / |Resolution of racemate; |Enzymatic reaction View Scheme

beef liver catalase; porcine kidney D-amino acid oxidase in phosphate buffer Oxidation; pH=7; Enzymatic reaction;

hydrogenchloride; sodium nitrite in water 24 h; Ambient temperatureNaNO2: 1 equivalent;

lithium hydroxide; porcine kidney acylase 17 h; Yield given;

1: sodium hydrogen sulfite / 2 h / 20 °C 2: 9.5 g / tetrahydrofuran; H2O / 1 h / 55 °C 3: 83 percent / barium hydroxide / H2O / 72 h / Heating 4: triethylamine / H2O / 14 h / 20 °C 5: 3.69 g / porcine acylase I; LiOH / H2O / 72 h / 37 °C / pH 7.8 View Scheme

1: 9.5 g / tetrahydrofuran; H2O / 1 h / 55 °C 2: 83 percent / barium hydroxide / H2O / 72 h / Heating 3: triethylamine / H2O / 14 h / 20 °C 4: 3.69 g / porcine acylase I; LiOH / H2O / 72 h / 37 °C / pH 7.8 View Scheme

1: sodium nitrite / water; acetic acid / 0 - 90 °C 2: hydrogenchloride; water / acetic acid / 0.5 h / 90 °C View Scheme