sulfuric acid in tetrahydrofuran; water T=20°C; pH=1.7;

sodium tetrahydroborate; cerium(III) chloride in methanol further reag.: (S)-BINAL-H;

sodium hydrogencarbonate in water T=90°C; Retro Diels-Alder Reaction; 2 - 2.5 h;

sodium hydrogencarbonate in tert-butyl methyl ether; water; toluene T=90°C; retro Diels-Alder Reaction; 2 - 2.5 h;

1: 87 percent / bromine / methanol / 0.5 h / Ambient temperature 2: 84 percent 3: 86 percent / 2N sodium hydroxide / H2O; CH2Cl2 5: N-methylmorpholine N-oxide, selenium dioxide 6: imidazole / dimethylformamide 7: 33 percent / NaBH4, CeCl3*6H2O / methanol / further reag.: (S)-BINAL-H View Scheme

1: 42 percent / imidazole / dimethylformamide / 1.5 h / 20 °C 2: 1.) ozone 2.) PPh3 / 1.) CH2Cl2, MeOH, -60 deg C 2.) CH2Cl2, MeOH, -60 to 0 deg C 3: NaHCO3 / aq. ethanol / Heating 5: N-methylmorpholine N-oxide, selenium dioxide 6: imidazole / dimethylformamide 7: 33 percent / NaBH4, CeCl3*6H2O / methanol / further reag.: (S)-BINAL-H View Scheme

1: 42 percent / imidazole / dimethylformamide / 1.5 h / 20 °C 2: 1.) ozone 2.) PPh3 / 1.) CH2Cl2, MeOH, -60 deg C 2.) CH2Cl2, MeOH, -60 to 0 deg C 3: NaHCO3 / aq. ethanol / Heating 5: N-methylmorpholine N-oxide, selenium dioxide 6: imidazole / dimethylformamide 7: 33 percent / NaBH4, CeCl3*6H2O / methanol / further reag.: (S)-BINAL-H View Scheme

1: liq. SO2 / 0.5 h / Heating 2: 42 percent / imidazole / dimethylformamide / 1.5 h / 20 °C 3: 1.) ozone 2.) PPh3 / 1.) CH2Cl2, MeOH, -60 deg C 2.) CH2Cl2, MeOH, -60 to 0 deg C 4: NaHCO3 / aq. ethanol / Heating 6: N-methylmorpholine N-oxide, selenium dioxide 7: imidazole / dimethylformamide 8: 33 percent / NaBH4, CeCl3*6H2O / methanol / further reag.: (S)-BINAL-H View Scheme

2: N-methylmorpholine N-oxide, selenium dioxide 3: imidazole / dimethylformamide 4: 33 percent / NaBH4, CeCl3*6H2O / methanol / further reag.: (S)-BINAL-H View Scheme

1: N-methylmorpholine N-oxide, selenium dioxide 2: imidazole / dimethylformamide 3: 33 percent / NaBH4, CeCl3*6H2O / methanol / further reag.: (S)-BINAL-H View Scheme