2',3'-Dideoxy- and 3'-Azido-2',3'-dideoxynucleosides of 5-Phenyl-2(1H)-pyrimidinone. Preparation of 2',3'-Dideoxypentofuranoses

Abstract

The synthesis of methyl 3-azido-5-benzoyl-2,3-dideoxy-β-D-ribofuranoside (10) from methyl 2-deoxy-D-ribofuranoside (1) and its use for the preparation of 3'-azido-2',3'-dideoxy-β-D-ribofuranosides is described. Reaction of methylglucoside 1 with benzoyl chloride in pyridine afforded 5-O-benzoyl derivative 2, which on oxidation with complex of chromium trioxide, pyridine and acetic anhydride afforded 3-keto derivative 3. This was reduced with sodium borohydride in ethanol to give a mixture of methyl 2-deoxyglycosides of α-D-ribo- (4) and β-D-xylo- (5) configuration. Their mesyl derivatives 6 and 7 were chromatographically separated. Compound 7 reacted with sodium azide in hot dimethylformamide to afford methyl 3-azido-5-O-benzoyl-2,3-dideoxy-β-D-ribofuranoside (10). 5-Phenyl-2(1H)-pyrimidinone was converted into silyl derivative 11 by treatment with hexamethyldisilazane. Reaction of compound 11 with the azido sugar 10, catalyzed by trimethylsilyl trifluoromethanesulfonate, and subsequent methanolysis, furnished a mixture of anomeric 3'-azido-2',3'-dideoxynucleosides 14 and 15. Methyl 5-O-benzoyl-2,3-dideoxy-α-D-ribofuranoside (17) was prepared from methyl-α-glycoside 4 by reaction with thionyl chloride and subsequent reduction of the obtained 3-chloro derivative 16 with tributylstannane. Silyl derivative 11 reacted with 2,3-dideoxy sugar 17 under catalysis with trimethylsilyl triflate to give mainly 1-(5-O-benzoyl-2,3-dideoxy-α-D-glycero-pentofuranosyl)-5-phenyl-2(1H)-pyrimidinone (19) and minor amount of the β-anomer 18. Their methanolysis afforded dideoxynucleosides 20 and 21.