Phenyl thioxochloroformate → ((2S,3R,5S)-3-(benzoyloxy)-5-(2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)tetrahydrofuran-2-yl)methyl benzoate

Participants

Reaction Steps

To a solution of 1-(3,5-di-O-benzoyl-β-L-arabinofuranosyl)uracil 12 (5.2 g, 11.4 mmol) in anhydrous 1,2-dichloroethane (120 mL) were added phenoxythiocarbonyl chloride (4.7 mL, 34.3 mL) and 4-(dimethylamino)pyridine (DMAP, 12.5 g, 102.6 mmol). The resulting solution was stirred at room temperature under argon atmosphere for 1 h and then evaporated under reduced pressure. The residue was dissolved in dichloromethane (300 mL) and the organic solution was successively washed with an ice-cold 0.2 N hydrochloric acid solution (3×200 mL) and water (2×200 mL), dried over Na2SO4 then evaporated under reduced pressure. The crude material was coevaporated several times with anhydrous dioxane and dissolved in this solvent (110 mL). To the resulting solution were added under argon tris-(trimethylsilyl)silane hydride (4.2 mL, 13.7 mmol) and α,α′-azoisobutyronitrile (AIBN, 0.6 g, 3.76 mmol). The reaction mixture was heated and stirred at 100° C. for 1 h under argon, then cooled to room temperature and evaporated under reduced pressure. The residue was purified by silica gel column chromatography [eluent: stepwise gradient of methanol (0-5%)] to give 13 (2.78 g, 56%) which was crystallized from EtOH: mp=223-225° C.; H-NMR (DMSO-d6): δ 11.4 (br s, 1H, NH), 8.0-7.5 (m, 11H, 2 C6H5CO, H-6), 6.28 (t, 1H, H-1′, J=7 Hz), 5.5 (m, 2H, H-1′ and H-5), 4.6-4.4 (m, 3H, H-4′, H-5′ and H-5″), 2.6 (m, 2H, H-2′ and H-2″); MS: FAB>0 (matrix GT) m/z 437 (M+H)+, 3325 (S)+; FAB<0 (matrix GT) m/z 435 (M−H)−, 111 (B)−; Anal. Calcd for C23H20N2O7: C, 63.30; H, 4.62; N, 6.42. Found: C, 62.98; H, 4.79; N, 6.40.

Provenance & Evidence