1: pyridine, CSA / CH2Cl2 / 1 h / Ambient temperature 2: 88 percent / K2CO3 / methanol / 60 h / Ambient temperature 3: 90 percent / 2,6-lutidine / CH2Cl2 4: 1.) dicyclohexylmagnesium bromide / 1.) THF, -65 to -50 deg C, 35 min, 2.) THF, -65 to -50 deg C, 40 min 5: 93 percent / TBAF / tetrahydrofuran / 34 h / Ambient temperature 6: 3 Angstroem molecular sieves, TFA / CH2Cl2 / 0.6 h / Ambient temperature View Scheme