silica gel in chloroform T=60°C; 27 h;

aluminum oxide in hexane T=60°C; 24 h;

1: 88 percent / triethylamine / dimethylformamide / 24 h / 95 °C 2: 96 percent / TiCl4 / CH2Cl2 / 1.5 h / -78 °C 3: 90 percent / p-toluenesulfonic acid / benzene / 2 h / Heating 4: 81 percent / TiCl4 / CH2Cl2 5: 71 percent / NaNH2 / benzene 6: 1.) O3; 2.) Zn/CH3COOH / 1.) -78 deg C, 30 min; 2.) room temperature overnight. 7: 73 percent / HCl / acetic acid / 21 h / Ambient temperature 8: 81 percent / SiO2 / CHCl3 / 27 h / 60 °C View Scheme

1: 90 percent / p-toluenesulfonic acid / benzene / 2 h / Heating 2: 81 percent / TiCl4 / CH2Cl2 3: 71 percent / NaNH2 / benzene 4: 1.) O3; 2.) Zn/CH3COOH / 1.) -78 deg C, 30 min; 2.) room temperature overnight. 5: 73 percent / HCl / acetic acid / 21 h / Ambient temperature 6: 81 percent / SiO2 / CHCl3 / 27 h / 60 °C View Scheme

1: 96 percent / TiCl4 / CH2Cl2 / 1.5 h / -78 °C 2: 90 percent / p-toluenesulfonic acid / benzene / 2 h / Heating 3: 81 percent / TiCl4 / CH2Cl2 4: 71 percent / NaNH2 / benzene 5: 1.) O3; 2.) Zn/CH3COOH / 1.) -78 deg C, 30 min; 2.) room temperature overnight. 6: 73 percent / HCl / acetic acid / 21 h / Ambient temperature 7: 81 percent / SiO2 / CHCl3 / 27 h / 60 °C View Scheme

1: p-toluenesulfonic acid monohydrate / ethanol / 3 h / Ambient temperature 2: 81 percent / TiCl4 / CH2Cl2 3: 71 percent / NaNH2 / benzene 4: 1.) O3; 2.) Zn/CH3COOH / 1.) -78 deg C, 30 min; 2.) room temperature overnight. 5: 73 percent / HCl / acetic acid / 21 h / Ambient temperature 6: 81 percent / SiO2 / CHCl3 / 27 h / 60 °C View Scheme

1: 81 percent / TiCl4 / CH2Cl2 2: 71 percent / NaNH2 / benzene 3: 1.) O3; 2.) Zn/CH3COOH / 1.) -78 deg C, 30 min; 2.) room temperature overnight. 4: 73 percent / HCl / acetic acid / 21 h / Ambient temperature 5: 81 percent / SiO2 / CHCl3 / 27 h / 60 °C View Scheme

1: methanephosphonic acid dimethyl ester With n-butyllithium in tetrahydrofuran; hexane T=-78°C; 0.0833333 h; 2: (4R,4aS)-(-)-4,4a-dimethyl-6-isopropylidene-3,4,4a,5,6,7-hexahydrochromen-2-one in tetrahydrofuran; hexane T=-78 - -20°C; Belleau-Fujimoto reaction; 3 h;

1: 73 percent / HCl / acetic acid / 21 h / Ambient temperature 2: 81 percent / SiO2 / CHCl3 / 27 h / 60 °C View Scheme

1: 72 percent / NaNH2 / benzene / 1.) reflux, 5 h; 2.) 45 deg C, 17.5 h. 2: 1.) mercuric acetate; 2.) LiCl, PdCl2, CuCl2. / 1.) room temperature, CH3OH, 15 min; 2.) 55 deg C, CH3OH, 1 hour. 3: 73 percent / HCl / acetic acid / 21 h / Ambient temperature 4: 81 percent / SiO2 / CHCl3 / 27 h / 60 °C View Scheme