| abstract |
The invention provides a compound of formula (I) wherein B is a nucleobase; U is O or S; Rx is -OC(=O)Ry, -OC(=O)CH(Ry)NH2, -OCH2OC(=O)Ry; Ry is optionally substituted alkyl or alkenyl or the side chain of a natural or unnatural amino acid R1 is H, or optionally substituted phenyl, benzyl, naphthyl, pyridyl or indolyl, or Rx and R1 together define a bond thus forming a cyclic phosphate; R2 and R2' together define the side chain of a natural or unnatural amino acid; R3 is optionally substituted alkyl, cycloalkyl, phenyl or benzyl; and pharmaceutically acceptable salts and compositions thereof which are useful in the treatment of cancer, especially leukemias. |