NUCLEOSIDES .51. THE 2-(4-NITROPHENYL)ETHOXYCARBONYL (NPEOC) AND 2-(2,4-DINITROPHENYL)ETHOXYCARBONYL (DNPEOC) GROUPS FOR PROTECTION OF HYDROXY FUNCTIONS IN RIBONUCLEOSIDES AND 2'-DEOXYRIBONUCLEOSIDES

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-dinitro-phenyl)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 detritylated to 16, 38, 51, and 65, respectively, or converted by 1,8-diazabicyclo[5.4.0]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 H-1-NMR spectra.