N(3)-Histidylriboflavin

N(3)-Methyl-2'-deoxycytidine

N(3)-Methyl-3'-azido-3'-deoxythymidine 5'-triphosphate

N(3)-Methyltetraacetylriboflavin

N(3)-Phenacyluridine

N(4)(5-Amino-pentyl)cytidine

N(4), N(4), O(2')-trimethylcytidine

N(4), N(4)-Dimethyl-5-azacytidine

N(4), O(2')-Dimethylcytidine

N(4)-(1(b), 2(a), 3(a)-Trihydroxy-4(b)-1, 2, 3, 4-tetrahydronaphthyl)-2'-deoxycytidine

N(4)-(2-Acetoxyethoxymethyl)-2-acetylpyridine thiosemicarbazone

N(4)-(4-Bromophenyl)-N(2)-methyl-5-nitroso-2, 4, 6-pyrimidinetriamine

N(4)-(4-Carboxybutyryl)-1-beta-arabinofuranosylcytosine

N(4)-(6-Aminohexyl)cytidine 5'-triphosphate

N(4)-(6-Aminohexyl)deoxycytidine 5'-triphosphate

N(4)-(Guanosin-7-yl)-4-aminoquinoline 1-oxide

N(4)-Acetylspermidine

N(4)-Acetylsulfadiazine

N(4)-Acetylsulfadimethoxine

N(4)-Acetylsulfadoxine