1: (2R,3S)-5-oxo-2-tridecyltetrahydrofuran-3-carboxylic acid With Stile's reagent in N,N-dimethyl-formamide T=135°C; 60 h; Inert atmosphere; 2: formaldehyd With sodium acetate; acetic acid; N-methylaniline in water T=20°C; 3 h;

1: in N,N-dimethyl-formamide T=135 - 140°C; 70 h; 2: With formaldehyd; sodium acetate; acetic acid in water T=20°C; 2 h;

hydrogenchloride in water; butanone 2 h; Heating;

1: 83 percent / Na2CO3, NaIO4, KMnO4 / H2O; tetrahydrofuran / 0.5 h / Ambient temperature 2: 55 percent / NaIO4 / methanol; H2O; benzene / 50 h / Ambient temperature 3: 85 percent / toluene / 1 h / 110 °C View Scheme

1.1: 72 percent / BF3*OEt2; HgO / tetrahydrofuran; H2O / 2.5 h / 20 °C 2.1: dimethylformamide / 70 h / 135 - 140 °C 2.2: 72 percent / NaOAc; HOAc; formalin / H2O; various solvent(s) / 2 h / 20 °C View Scheme

1.1: NEt3 1.2: methanesulfonamide; AD mix-β(R) 2.1: 86 percent / NEt3; mesyl chloride / CH2Cl2 / 0.25 h / 0 °C 3.1: nBuLi / hexane; tetrahydrofuran / 1.5 h / -78 °C 3.2: 87 percent / tetrahydrofuran; hexane / 2 h / -78 °C 4.1: 72 percent / BF3*OEt2; HgO / tetrahydrofuran; H2O / 2.5 h / 20 °C 5.1: dimethylformamide / 70 h / 135 - 140 °C 5.2: 72 percent / NaOAc; HOAc; formalin / H2O; various solvent(s) / 2 h / 20 °C View Scheme

1.1: lithium diisopropylamide / tetrahydrofuran / 2 h / -78 - 0 °C 1.2: 2 percent / tetrahydrofuran / 3 h / -78 - 20 °C 2.1: 74 percent / Pyrolysis 3.1: 72 percent / hydrochloric acid / H2O; butan-2-one / 2 h / Heating View Scheme

bei der Ozonspaltung; (-)-protolichesterolic acid;

(-)-protolichesterolic acid;

T=155 - 160°C; im Rohr; (+)-protolichesterolic acid;