| Abstract: | The Common 2′ -deoxypyrimidine and -purine nucleosides, thymidine ( 4 ), O4-2-(4-nitrophenyl)ethyl]-thymidine ( 17 ), 2′-deoxy-N4-2-(4-nitrophenyl)ethoxycarbonyl]cytidine ( 26 ), 2′-deoxy-N6-2-(4-nitrophenyl)-ethoxycarbonyl]adenosine- 39 , and 2′-deoxy-N2-2-(4-nitrophenyl)(ethoxycarbonyl]-O6-2–4-nitrophenyl)ethyl]-guanosine ( 52 ) were further protected by the 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) and the 2-(2,4-dinitrophenyl)ethoxycarbonyl (dnpeoc) group at the OH functions of the sugar moiety to form new partially and fully blocked intermediates for nucleoside and nucleotide syntheses. The corresponding 5′-O-monomethoxytrityl derivatives 5 , 18 , 30 , 40 , and 56 were also used as starting material to synthesize some other intermediates which were not obtained by direct acylations. In the ribonucleoside series, the 5′ -O-monomethoxytrityl derivatives 14 , 36 , 49 , and 63 reacted with 2-(4-nitrophenyl) ethyl chloroformate ( 1 ) to the corresponding 2′,3′-bis-carbonates 15 , 37 , 50 , and 64 which were either detriylated to 16 , 38 , 51 , and 65 , respectively, or converted by 1,8-diazabicyclo5.4.0]undec-7-ene (DBU) treatment to the 2′,3′-cyclic carbonates 66 – 69 . The newly synthesized compounds were characterized by elemental analyses and UV and 1H-NMR spectra. |
