1: MeONa / methanol / 12 h 2: H2S, Et3N / pyridine; methanol / 16 h / 22 °C View Scheme

1: 98.4 percent / BF3*OEt2; molecular sieves 4 Angstroem / CH2Cl2 / -20 °C 2: triphenylphosphine / tetrahydrofuran; H2O / 45 °C 3: 232 mg / triethylamine; 1-hydroxybenzotriazole; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride / CH2Cl2 / 10 h / 20 °C 4: 85 percent / sodium methoxide / methanol; CH2Cl2 / 12 h / 20 °C / pH 9 View Scheme

sodium methylate in methanol 12 h;