1: sodium tetrahydroborate / water / |Inert atmosphere 2: triethylamine / |Inert atmosphere View Scheme

1: diethyl ether / a) 0 deg C, 2 h, b) RT, overnight 2: 92 percent / HCl / dioxane; diethyl ether / 1 h / 0 °C 3: 50 percent / NaBH4 / tetrahydrofuran; H2O / 0.75 h / 0 °C View Scheme

1: sodium tetrahydroborate / water / |Inert atmosphere 2: triethylamine / |Inert atmosphere View Scheme

1: CH2Cl2 / 2 h / -35 - 0 °C 2: 85.4 percent / anisole, HCl / dioxane; CH2Cl2 / 1.25 h / 0 - 20 °C 3: 86.7 percent / HOBT, 1-ethyl-3-<3-(N,N-dimethylamino)propyl>carbodiimide (WSCD) / dimethylformamide / 3 h / 0 - 20 °C 4: HCl / dioxane; CH2Cl2 / 1.17 h / 0 - 20 °C 5: 94.7 percent / HOBT, 1-ethyl-3-<3-(N,N-dimethylamino)propyl>carbodiimide (WSCD) / dimethylformamide / 3.5 h / 0 - 20 °C 6: 100 percent / HCl / CH2Cl2; dioxane / 1.17 h / 0 - 20 °C 7: 82.4 percent / Et3N / CH2Cl2 / 0.33 h / -15 °C View Scheme

tetra(n-butyl)ammonium hydroxide in water; dimethyl sulfoxide T=0°C; 0.5 h;

1: NMM / dimethylformamide / 20 h / -20 °C 2: 90 percent / 1.5 N HCl/AcOH 3: 97 percent / HOBt*H2O, NEt3 / dimethylformamide / 23 h 4: 95 percent / 1.5 N HCl/AcOH / 1 h 5: 90 percent / HOBt*H2O, NEt3, DCC / dimethylformamide / a) -5 deg C to 0 deg C, 1 h, b) 20 deg C, 24 h 6: 86 percent / 0.5 M NaOH / acetone / 1.5 h View Scheme

1: trimethyl-oxo-sulfonium iodide With potassium tert-butylate in tetrahydrofuran T=90°C; 2 h; 2: Boc-Phe-O-COO-isoBu in tetrahydrofuran T=0°C; 2.75 h; Product distribution / selectivity;