(3R,4R,5R)-3,4-Bis(benzoyloxy)-5-(benzoyloxymethyl)tetrahydrofuran-2-carboxylic acid (3,4,6-Tri-O-benzoyl-2,5-anhydro-D-allonic acid, 2 g, 4 mmol) was dissolved in anhydrous THF (40 mL) under argon. Triphenylphosphine (2.1 g, 8 mmol) was then added, and the resulting mixture was stirred until it was completely dissolved. Subsequently 2,2′-dipyridyldisulfide (1.8 g, 8 mmol) was added to the reaction mixture. The mixture was stirred at room temperature for 2 hours, after which 3-methoxy-N-methylaniline (0.7 g, 5.6 mmol) was added and stirring was continued at room temperature for 16 hours. The solvent was evaporated to dryness, the residue was dissolved in chloroform (150 mL), the solution was washed twice with 0.1M NaOH solution (100 mL), twice with 0.2 M HCl solution (100 mL), once with saturated NaHCO3 solution (100 mL), and dried (Na2SO4). The solution was evaporated to dryness and the residue dissolved in 7M solution of ammonia in methanol (250 mL). The solution was stirred for 16 hours at room temperature and evaporated to dryness. The residue was dissolved in chloroform and applied to a column of silica gel. Elution with a mixture of chloroform-methanol (3:1) and evaporation of the appropriate fractions yielded the title compound as a colorless oil (0.51 g, 1.7 mmol, 42%): MS (ES) m/z 399 [M+H+C6H15N]+, 296 [M−H]−.
