1: N,N-dimethylaminopyridine / diethyl ether 2: 80 percent / tetra-n-butylammonium fluoride / tetrahydrofuran / 0.5 h / 5 °C 3: 90 percent / aq.NaOH / methanol / 2.5 h / 5 - 25 °C 4: 99 percent / methanol; diethyl ether / 15 h / Ambient temperature View Scheme

1: potassium acetate / 1.5 h / 70 °C 2: 1.) water / 1.) conc. HCl / 1.) methanol, room temp., 1h; 2.) re-acetylation 3: 83 percent / tetra-n-butylammonium fluoride / tetrahydrofuran / 0.5 h / 5 °C 4: 1.) and 2.) NaOH / 1.) in methanol-water, 5 deg C, 0.5h; 2.) room temp., 2h View Scheme