The present invention relates to novel compounds according to the to the general formulas I, II, III, IV or V: wherein B is
nucleoside base according to the structure: R is H, F, Cl, Br, I, C1-C4
alkyl (preferably CH3), -C=N, -C=C-Ra, X is H, C1-C4
alkyl (preferably, CH3), F, Cl, Br or I; Z is O or CH2, with the proviso that Z is CH2 and not O when the compound is according to general formula II, R<3 >is -C=C-H and R<2 >is H or a
phosphate, diphosphate, triphosphate or phosphotriester group; R<1 >is H, an
acyl group, a C1-C20
alkyl or an
ether group; R<2 >is H, an
acyl group, a C1-C20 alkyl or
ether group, a
phosphate, diphosphate, triphosphate, phosphodiester group or a group; Nu is a radical of a biologically active antiviral compound such that an amino group or hydroxyl group from said biologically active antiviral compound forms a
phosphate,
phosphoramidate,
carbonate or urethane group with the adjacent
moiety; R<8 >is H, or a C1-C20 alkyl or
ether group, preferably a C1-C12 alkyl group; k is 0-12, preferably, 0-2; R<3 >is selected from a C1-C4 alkyl (preferably, CH3), -(CH2)n-C=C-Ra, R<3a >and R<3b >are independently selected from H, F, Cl, Br or I; R<4 >and R<5 >are independently selected from H, F, Cl, Br, I, OH, C1-C4 alkyl (preferably, CH3), -(CH2)n-C=C-Ra, with the proviso that R<4 >and R<5 >are not both H; Ra is H, F, Cl, Br, I, or -C1-C4 alkyl, preferably H or CH3; Y is H, F, Cl, Br, I or -C1-C4 alkyl, preferably H or CH3; and n is 0, 1, 2, 3, 4 or 5, preferably 0, 1 or 2; and their anomers, pharmaceutically acceptable salts, solvates, or polymorphs thereof.