1: 59.8 percent / dicyclohexylcarbodiimide / tetrahydrofuran / 20 °C 2: 55.8 percent / diphenylphosphoryl azide; triethylamine / 7 h / Heating 3: 90.4 percent / tetrabutylammonium bromide; K2CO3; NaOH / ethyl acetate / 0.17 h / 20 °C 4: 91.1 percent / trifluoroacetic acid / CH2Cl2 / 1 h / 20 °C 5: 74.2 percent / 2,6-lutidine / dimethylformamide / 55 - 60 °C 6: 88.6 percent / 1 N aq. NaOH / ethanol / 2 h / 20 °C View Scheme

1: 59.8 percent / dicyclohexylcarbodiimide / tetrahydrofuran / 20 °C 2: 55.8 percent / diphenylphosphoryl azide; triethylamine / 7 h / Heating 3: 90.4 percent / tetrabutylammonium bromide; K2CO3; NaOH / ethyl acetate / 0.17 h / 20 °C 4: 91.1 percent / trifluoroacetic acid / CH2Cl2 / 1 h / 20 °C 5: 74.2 percent / 2,6-lutidine / dimethylformamide / 55 - 60 °C 6: 88.6 percent / 1 N aq. NaOH / ethanol / 2 h / 20 °C View Scheme

1: 55.8 percent / diphenylphosphoryl azide; triethylamine / 7 h / Heating 2: 90.4 percent / tetrabutylammonium bromide; K2CO3; NaOH / ethyl acetate / 0.17 h / 20 °C 3: 91.1 percent / trifluoroacetic acid / CH2Cl2 / 1 h / 20 °C 4: 74.2 percent / 2,6-lutidine / dimethylformamide / 55 - 60 °C 5: 88.6 percent / 1 N aq. NaOH / ethanol / 2 h / 20 °C View Scheme

1: 90.4 percent / tetrabutylammonium bromide; K2CO3; NaOH / ethyl acetate / 0.17 h / 20 °C 2: 91.1 percent / trifluoroacetic acid / CH2Cl2 / 1 h / 20 °C 3: 74.2 percent / 2,6-lutidine / dimethylformamide / 55 - 60 °C 4: 88.6 percent / 1 N aq. NaOH / ethanol / 2 h / 20 °C View Scheme