Novel 2- and 4-substituted
pyrimidine nucleosides and oligonucleosides are provided, as are methods and intermediates useful in preparing same. In preferred embodiments, one of the 2- and 4-substituents is =O, =NH, or =NH2+ and the other is Q, =C (RA)-Q, C(RA)(RB)-C(RC)(RD)-Q, C (RA)=C(RC)-Q or C 3BOND C-Q, where RA, RB, RC and RD independently are H, SH, OH, NH2, or C1-C20
alkyl, or one of (RA)(RB) or (RC)(RD) is =O, and Q is
halogen,
hydrogen, C1-C20
alkyl, C1-C20 alkylamine, C1-C20
alkyl-N-
phthalimide, C1-C20 alkylimidazole, C1-C20 alkylbis-
imidazole,
imidazole, bis-
imidazole, amine, N-
phthalimide, C2-C20 alkenyl, C2-C20 alkynyl, hydroxyl,
thiol, keto, carboxyl, nitrates, nitro,
nitroso,
nitrile,
trifluoromethyl, trifluoromethoxy, O-alkyl, S-alkyl, NH-alkyl, N-dialkyl, O-aralkyl, S-aralkyl, NH-aralkyl, azido, hydrazino, hydroxylamino, isocyanato,
sulfoxide,
sulfone,
sulfide, disulfide, silyl, O-(hydroxyl
protecting group), a
leaving group, a heterocycle, an intercalator, a reporter molecule, a conjugate, a
polyamine, a
polyamide, a
polyethylene glycol, a polyether, or a depurination enhancing group.