1: diethyl ether 2: 340 mg / NaOMe / methanol 3: Et3N / CH2Cl2 / 0 °C 4: 257 mg / Na2S*H2O; sulfur / dimethylformamide / 24 h / 80 °C View Scheme

1: 90 percent / NaBH4 / methanol / 0 °C 2: diethyl ether 3: 340 mg / NaOMe / methanol 4: Et3N / CH2Cl2 / 0 °C 5: 257 mg / Na2S*H2O; sulfur / dimethylformamide / 24 h / 80 °C View Scheme

1: 70 percent / H2SO4 conc. / 10 h / Heating 2: 84 percent / Ba(OH)2*8H2O / methanol / Ambient temperature 3: 80 percent / Pb(OAc)4, Cu(OAc)2 / pyridine; benzene / 2 h / Heating 4: 1.) SeO2, TBHP, 2.) Me2S / 1.) CH2Cl2, 25 deg C, 30 h, 2.) AcOH, 4h 5: 1.) diborane, 2.) NaOAc, 30percent H2O2 / 1.) THF, 25 deg C, 2 h, 2.) THF-H2O, 25 deg C, 2 h 6: 80 percent / Et3N / CH2Cl2 / 0 deg C, 0.5 h; RT, 3 h 7: 70 percent / Na2S*H2O, S / dimethylformamide / 24 h / 90 °C View Scheme

1: 84 percent / Ba(OH)2*8H2O / methanol / Ambient temperature 2: 80 percent / Pb(OAc)4, Cu(OAc)2 / pyridine; benzene / 2 h / Heating 3: 1.) SeO2, TBHP, 2.) Me2S / 1.) CH2Cl2, 25 deg C, 30 h, 2.) AcOH, 4h 4: 1.) diborane, 2.) NaOAc, 30percent H2O2 / 1.) THF, 25 deg C, 2 h, 2.) THF-H2O, 25 deg C, 2 h 5: 80 percent / Et3N / CH2Cl2 / 0 deg C, 0.5 h; RT, 3 h 6: 70 percent / Na2S*H2O, S / dimethylformamide / 24 h / 90 °C View Scheme

1: 1.) SeO2, TBHP, 2.) Me2S / 1.) CH2Cl2, 25 deg C, 30 h, 2.) AcOH, 4h 2: 1.) diborane, 2.) NaOAc, 30percent H2O2 / 1.) THF, 25 deg C, 2 h, 2.) THF-H2O, 25 deg C, 2 h 3: 80 percent / Et3N / CH2Cl2 / 0 deg C, 0.5 h; RT, 3 h 4: 70 percent / Na2S*H2O, S / dimethylformamide / 24 h / 90 °C View Scheme

1: 80 percent / Pb(OAc)4, Cu(OAc)2 / pyridine; benzene / 2 h / Heating 2: 1.) SeO2, TBHP, 2.) Me2S / 1.) CH2Cl2, 25 deg C, 30 h, 2.) AcOH, 4h 3: 1.) diborane, 2.) NaOAc, 30percent H2O2 / 1.) THF, 25 deg C, 2 h, 2.) THF-H2O, 25 deg C, 2 h 4: 80 percent / Et3N / CH2Cl2 / 0 deg C, 0.5 h; RT, 3 h 5: 70 percent / Na2S*H2O, S / dimethylformamide / 24 h / 90 °C View Scheme

1: 1.) diborane, 2.) NaOAc, 30percent H2O2 / 1.) THF, 25 deg C, 2 h, 2.) THF-H2O, 25 deg C, 2 h 2: 80 percent / Et3N / CH2Cl2 / 0 deg C, 0.5 h; RT, 3 h 3: 70 percent / Na2S*H2O, S / dimethylformamide / 24 h / 90 °C View Scheme

sulfuric acid T=20°C;

sodium tetrahydroborate in methanol T=20°C; 1 h;