2: Et4NF / acetonitrile / Heating 3: 1.) O3, 2.) Me2S / 1.) CH2Cl2, -78 deg C, 4 min, 2.) CH2Cl2, -78 deg C, 15 min, then room t. 4: Et3N, MeOH / 0.08 h / Ambient temperature View Scheme

1: toluene-4-sulphonic acid / CH2Cl2 2: AgOAc / acetonitrile / Heating 3: 75 percent / aq.HOAc / 2 h / Ambient temperature View Scheme

1: 77 percent / pyridine / 17 h / 20 °C 2: 48 percent / 3 h / 180 °C 3: 64 percent / NaOEt / ethanol / 3 h / 0 °C 4: 92 percent / DMAP; pyridine / 13 h / 20 °C 5: 55 percent / NaN3 / dimethylformamide / 14 h / 60 °C 6: TMSBr / acetonitrile / 4 h / 40 °C View Scheme