trifluorormethanesulfonic acid in methanol T=80°C; 6.5 h;

sodium cyanoborohydride in methanol T=20°C; Condensation; Reduction; 2 h;

1: Me4NOH*5H2O / acetonitrile / 48 h / 20 °C 3: TFA / CH2Cl2 / 0.25 h / 20 °C 4: NaBH3CN / methanol / 2 h / 20 °C View Scheme

1.1: O3 / ethyl acetate / -78 °C 1.2: aq. HCl / 26 h / 0 - 100 °C 2.1: Me4NOH*5H2O / acetonitrile / 48 h / 20 °C 4.1: TFA / CH2Cl2 / 0.25 h / 20 °C 5.1: NaBH3CN / methanol / 2 h / 20 °C View Scheme

1: 97 percent / imidazole / dimethylformamide / 3.5 h / 23 °C 2: 96 percent / TsOH / benzene / 0.5 h / Heating 3: LiBH4 / tetrahydrofuran; methanol / 24 h / 23 °C 4: DMSO, (COCl)2, Et3N / CH2Cl2 / 1.5 h / -78 °C 5: 1.) LDA / 1.) THF, -78 deg C 6: 87 percent / H2 / Pd/C / ethanol / 24 h / 23 °C View Scheme

1: 97 percent / imidazole / dimethylformamide / 3.5 h / 23 °C 2: 96 percent / TsOH / benzene / 0.5 h / Heating View Scheme

1: 97 percent / imidazole / dimethylformamide / 3.5 h / 23 °C 2: 96 percent / TsOH / benzene / 0.5 h / Heating 3: LiBH4 / tetrahydrofuran; methanol / 24 h / 23 °C View Scheme

1: 97 percent / imidazole / dimethylformamide / 3.5 h / 23 °C 2: 96 percent / TsOH / benzene / 0.5 h / Heating 3: LiBH4 / tetrahydrofuran; methanol / 24 h / 23 °C 4: DMSO, (COCl)2, Et3N / CH2Cl2 / 1.5 h / -78 °C 5: 1.) LDA / 1.) THF, -78 deg C 6: 87 percent / H2 / Pd/C / ethanol / 24 h / 23 °C 7: 90 percent / 5percent HF / acetonitrile / 9 h / 23 °C View Scheme

1: 97 percent / imidazole / dimethylformamide / 3.5 h / 23 °C 2: 96 percent / TsOH / benzene / 0.5 h / Heating 3: LiBH4 / tetrahydrofuran; methanol / 24 h / 23 °C 4: DMSO, (COCl)2, Et3N / CH2Cl2 / 1.5 h / -78 °C 5: 1.) LDA / 1.) THF, -78 deg C 6: 87 percent / H2 / Pd/C / ethanol / 24 h / 23 °C 7: 90 percent / 5percent HF / acetonitrile / 9 h / 23 °C 8: 73 percent / DMSO, (COCl)2, Et3N / CH2Cl2 / 2 h / -78 °C 9: 95 percent / NaClO2, NaH2PO4 / 2-methyl-propan-2-ol; various solvent(s) / 0.25 h / 23 °C 10: 95 percent / 1,3-propanedithiol, 2percent HCl (gas) / various solvent(s) / 6 h / 50 °C View Scheme