2',3'-DIDEOXYNUCLEOSIDE AND 3'-AZIDO-2',3'-DIDEOXYNUCLEOSIDE OF 5-PHENYL-2(1H)-PYRIMIDINONE - PREPARATION OF 2',3'-DIDEOXYPENTOFURANOSES

The synthesis of methyl -azido-5-benzoyl-2,3-dideoxy-beta-D-ribofurano side (10) from methyl 2-deoxy-D-ribofuranoside (1) and its use for the preparation of 3'-azido-2',3'-dideoxy-beta-D-ribofuranosides is descr ibed. 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 deriv ative 3. This was reduced with sodium borohydride in ethanol to give a mixture of methyl 2-deoxyglycosides of alpha-D-ribo- (4) and beta-D-x ylo- (5) configuration. Their mesyl derivatives 6 and 7 were chromatog raphically separated Compound 7 reacted with sodium azide in hot dimet hylformamide to afford methyl zido-5-O-brnzoyl-2,3-dideoxy-beta-D-ribo furanoside (10). 5-Phenyl-2(1H)-pyrimidinone was converted into silyl derivative 11 by treatment with hexamethyldisilazane. Reaction of comp ound 11 with the azido sugar 10, catalyzed by trimethylsilyl trifluoro methanesulfonate, and subsequent methanolysis, furnished a mixture of anomeric 3'-azido-2',3'-dideoxynucleosides 14 and 15. Methyl 5-0-benzo yl-2,3-dideoxy-alpha-D-ribofuranoside (17) was prepared from methyl-al pha-glycoside 4 by reaction with thionyl chloride and subsequent reduc tion of the obtained 3-chloro derivative 16 with tributylstannane. Sil yl derivative 11 reacted with 2,3-dideoxy sugar 17 under catalysis wit h trimethylsilyl triflate to give mainly oyl-2,3-dideoxy-alpha-D-glyce ro-pentofuranosyl)-5- phenyl-2(1H)-pyrimidinone (19) and minor amount of the beta-anomer 18. Their methanolysis afforded dideoxynucleosides 20 and 21.