1: 1-(mercaptomethyl)-cyclopropaneacetic acid With sodium t-butanolate; PEG-600 in toluene Inert atmosphere; 2: montelukast sodium salt in tetrahydrofuran; toluene T=20°C; Inert atmosphere;

1.1: B-chloro-diisopinocampheylborane / dichloromethane / -5 - 0 °C 2.1: cerium(III) chloride / tetrahydrofuran / 0 - 5 °C 3.1: 4-(N,N-dimethlyamino)pyridine; triethylamine / dichloromethane / 0 - 5 °C 4.1: toluene-4-sulfonic acid / dichloromethane / 25 - 30 °C 5.1: water; sodium hydroxide / tetrahydrofuran; methanol / 25 - 30 °C 6.1: hydrogenchloride / water; ethyl acetate / 25 - 30 °C 7.1: N-ethyl-N,N-diisopropylamine / dichloromethane / 25 - 30 °C 7.2: 1 h / 0 - 5 °C 8.1: sodium methylate / methanol; N,N-dimethyl-formamide / 0 - 5 °C 9.1: ethyl acetate / 25 - 30 °C 10.1: sodium methylate / methanol; N,N-dimethyl-formamide / 26 h / 25 - 45 °C 11.1: sulfuric acid; water / 2.5 h / 0 - 10 °C / Inert atmosphere View Scheme

1.1: cerium(III) chloride / tetrahydrofuran / 0 - 5 °C 2.1: 4-(N,N-dimethlyamino)pyridine; triethylamine / dichloromethane / 0 - 5 °C 3.1: toluene-4-sulfonic acid / dichloromethane / 25 - 30 °C 4.1: water; sodium hydroxide / tetrahydrofuran; methanol / 25 - 30 °C 5.1: hydrogenchloride / water; ethyl acetate / 25 - 30 °C 6.1: N-ethyl-N,N-diisopropylamine / dichloromethane / 25 - 30 °C 6.2: 1 h / 0 - 5 °C 7.1: sodium methylate / methanol; N,N-dimethyl-formamide / 0 - 5 °C 8.1: ethyl acetate / 25 - 30 °C 9.1: sodium methylate / methanol; N,N-dimethyl-formamide / 26 h / 25 - 45 °C 10.1: sulfuric acid; water / 2.5 h / 0 - 10 °C / Inert atmosphere View Scheme

1.1: N-ethyl-N,N-diisopropylamine / acetonitrile / 0.5 h / 0 - 5 °C 1.2: 5 h / -25 °C 2.1: sodium methylate / methanol; N,N-dimethyl-formamide / 1 h / -15 °C 2.2: 10 h / -5 - 5 °C 3.1: water; sodium hydroxide / methanol / 3 h / 60 - 65 °C View Scheme

1: ethyl acetate / 25 - 30 °C 2: sodium methylate / methanol; N,N-dimethyl-formamide / 26 h / 25 - 45 °C 3: sulfuric acid; water / 2.5 h / 0 - 10 °C / Inert atmosphere View Scheme

sulfuric acid; water T=0 - 10°C; 2.5 h; Inert atmosphere;

1: sodium methylate / methanol; N,N-dimethyl-formamide / 0 - 5 °C 2: ethyl acetate / 25 - 30 °C 3: sodium methylate / methanol; N,N-dimethyl-formamide / 26 h / 25 - 45 °C 4: sulfuric acid; water / 2.5 h / 0 - 10 °C / Inert atmosphere View Scheme

1.1: water; sodium hydroxide / tetrahydrofuran; methanol / 25 - 30 °C 2.1: hydrogenchloride / water; ethyl acetate / 25 - 30 °C 3.1: N-ethyl-N,N-diisopropylamine / dichloromethane / 25 - 30 °C 3.2: 1 h / 0 - 5 °C 4.1: sodium methylate / methanol; N,N-dimethyl-formamide / 0 - 5 °C 5.1: ethyl acetate / 25 - 30 °C 6.1: sodium methylate / methanol; N,N-dimethyl-formamide / 26 h / 25 - 45 °C 7.1: sulfuric acid; water / 2.5 h / 0 - 10 °C / Inert atmosphere View Scheme

1: sodium methylate / methanol; N,N-dimethyl-formamide / 26 h / 25 - 45 °C 2: sulfuric acid; water / 2.5 h / 0 - 10 °C / Inert atmosphere View Scheme

1.1: N-ethyl-N,N-diisopropylamine / dichloromethane / 25 - 30 °C 1.2: 1 h / 0 - 5 °C 2.1: sodium methylate / methanol; N,N-dimethyl-formamide / 0 - 5 °C 3.1: ethyl acetate / 25 - 30 °C 4.1: sodium methylate / methanol; N,N-dimethyl-formamide / 26 h / 25 - 45 °C 5.1: sulfuric acid; water / 2.5 h / 0 - 10 °C / Inert atmosphere View Scheme