The present invention relates to the use of the compound according to formula (I), below for the treatment of tumors, cancer and hyperproliferative diseases, among other conditions or disease states: Where X is H or F; R1 and R2 are independently H, an acyl group, a C1-C20 alkyl or ether group, a phosphate, diphosphate, triphosphate or a phosphodiester group, a (A) or (B) group; Where Nu is a radical of a biologically active compound such as an anticancer, antiviral or antihyperproliferative 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 a C1-C12 alkyl group; k is 0-12, preferably, 0-2; and pharmaceutically acceptable salts thereof.