1: 90 percent / NaOMe / methanol / 24 h / Ambient temperature 2: 71 percent / pyridine / 1.25 h / Ambient temperature 3: 65 percent / tetrabutylammonium hydroxide, pyridine / acetonitrile / 48 h / Heating 4: 1.) NaH / 1.) DMF, -40 deg C, 0.75 h, 2.) DMF, a) from -40 to -30 deg C, 0.75 h, b) RT, 4 h 5: 71 percent / potassium t-butoxide / CH2Cl2 / 1.5 h / Ambient temperature 6: 40 percent / HCl / CH2Cl2; methanol / 0.75 h / Ambient temperature View Scheme

1: 65 percent / tetrabutylammonium hydroxide, pyridine / acetonitrile / 48 h / Heating 2: 1.) NaH / 1.) DMF, -40 deg C, 0.75 h, 2.) DMF, a) from -40 to -30 deg C, 0.75 h, b) RT, 4 h 3: 71 percent / potassium t-butoxide / CH2Cl2 / 1.5 h / Ambient temperature 4: 40 percent / HCl / CH2Cl2; methanol / 0.75 h / Ambient temperature View Scheme

1: 1.) NaH / 1.) DMF, -40 deg C, 0.75 h, 2.) DMF, a) from -40 to -30 deg C, 0.75 h, b) RT, 4 h 2: 71 percent / potassium t-butoxide / CH2Cl2 / 1.5 h / Ambient temperature 3: 40 percent / HCl / CH2Cl2; methanol / 0.75 h / Ambient temperature View Scheme

1: 71 percent / potassium t-butoxide / CH2Cl2 / 1.5 h / Ambient temperature 2: 40 percent / HCl / CH2Cl2; methanol / 0.75 h / Ambient temperature View Scheme

ammonium fluoride in methanol Ring cleavage; hydrolysis; 48 h; Heating;

1: 77 percent / Ag2O / toluene / 144 h 2: NaOMe / methanol / 96 h 3: 220 mg / NH4F / methanol / 48 h / Heating View Scheme

1: NaOMe / methanol / 96 h 2: 220 mg / NH4F / methanol / 48 h / Heating View Scheme

1: pyridine / 5 h / Ambient temperature 2: 96 percent / diisopropylammonium-tetrazolide / CH2Cl2 / Ambient temperature View Scheme