Ethyl Acetate → (2R,3R,4R,5R)-4-(Acetyloxy)-2-[(acetyloxy)methyl]-5-{2-cyano-6-[(2,2-diphenylethyl)amino]-9H-purin-9-yl}tetrahydro-3-furanyl acetate

Participants

Reaction Steps

N,O-Bistrimethylsilylacetamide (44 ml, 0.18 mol) was added to a suspension of 6-[(2,2-diphenylethyl)amino]-9H-purine-2-carbonitrile (10.0 g, 0.03 mol) (see WO-A-00/23457) in 1,1,1-trichloroethane (250 ml). The suspension was heated to reflux. When all suspended solid had dissolved the reaction mixture was allowed to cool to room temperature and the solvent was removed under reduced pressure. The residue was twice dissolved in toluene (50 ml) and the solvent removed under reduced pressure. The residue was then dissolved in toluene (100 ml) and (2R,3R,4R,5S)-4,5-bis(acetyloxy)-2-[(acetyloxy)methyl]tetrahydro-3-furanyl acetate (10.3 g, 0.032 mol) was added. The solution was stirred at room temperature and trimethylsilyltrifluoromethanesulphonate (16 ml, 0.088 mol) was carefully added. The resulting solution was heated under reflux for 2 hours and then allowed to cool to room temperature. The reaction mixture was diluted by the addition of ethyl acetate (100 ml) and then washed with saturated aqueous sodium hydrogen carbonate (ten portions of 100 ml) and saturated aqueous sodium chloride solution (100 ml). The aqueous extracts were combined and washed with ethyl acetate (three portions of 100 ml). The combined organic layers were dried (anhydrous magnesium sulphate) and the solvent was removed under reduced pressure to give a solid that was purified by column chromatography on silica gel eluting with dichloromethane:methanol:0.88 concentrated aqueous ammonia (97:3:0.5 by volume gradually changing to 80:20:3 by volume) to give the title compound as a foam (8.5 g).

Provenance & Evidence