1: 93 percent / 66percent aq. AcOH / 1 h / Ambient temperature 2: 1.) 10percent aq. H2SO4, 2.) Ac2O, pyridine / 1.) ethanol, 3.5 h View Scheme

1: 93 percent / 66percent aq. AcOH / 1 h / Ambient temperature 2: 1.) 10percent aq. H2SO4, 2.) Ac2O, pyridine / 1.) ethanol, 3.5 h 3: sodium cyanoborohydride, AcOH View Scheme