The present invention relates to the use of the compound according to formula (I) Where S is (A) or (B)； X is H or F； R1 is H, an acyl group, a C1-C20 alkyl or ether group, a phosphate, diphosphate, triphosphate or a phosphodiester group, a (C) or (D) group； Where Nu is a radical of a biologically active compound such as an anticancer, antihyperproliferative or antiviral compound such that an amino group or hydroxyl group from said biologically active agent forms a phosphate, phosphoramidate, carbonate or urethane group with the adjacent moiety； Each R8 is independently H, or a C1-C20 alkyl or ether group, preferably H or a C1-C2 alkyl group； k is 0-12, preferably, 0-2； R2 is H, an acyl group or a C1-C20 alkyl or ether group； and pharmaceutically acceptable salts, solvates or polymorphs thereof for the treatment of tumors, cancer and hyperproliferative diseases, among other conditions or disease states.
