methanol; silica gel 1.) CH2Cl2, -10 deg C, 15 min (the hemiacetal hydrolysed during chromatography); Yield given. Multistep reaction;

1: 1.) trifluoroacetic anhydride / 1.) toluene, r.t., overnight; 2.) r.t., 2 h 2: 53 percent / toluene / Heating View Scheme