1: 30percent aq. NaOH-MeOH / 4 h / Heating 2: 66 percent / 30percent aq. NaOH / tetrahydrofuran 3: 1.) AC2O; 2.) 2N NaOH / 1.) 3.5 h, reflux; 2.) MeOH, 1 min, reflux View Scheme

1: 30percent aq. NaOH-MeOH / 4 h / Heating 2: 66 percent / 30percent aq. NaOH / tetrahydrofuran 3: 1.) AC2O; 2.) 2N NaOH / 1.) 3.5 h, reflux; 2.) MeOH, 1 min, reflux 4: 73 percent / active MnO2 / acetone View Scheme

1: 30percent aq. NaOH-MeOH / 4 h / Heating 2: 8 percent / active MnO2, NaOH 3: 64 percent / hydrogen / 5percent Pd-C / methanol View Scheme