{5'-O-[Bis(4-methoxyphenyl)(phenyl)methyl]-2'-deoxy-β-D-threopentofuranosyl}thymine ethyl acetate 0.25-solvate

The title compound, C(31)H(32)N(2)O(7)·0.25C(4)H(8)O(2), is a key intermediate in the synthesis of [(18)F]fluorine-labelled thymidine ((18)F-FLT), which is the most widely used molecular imaging probe for positron emission tomography (PET). The crystallographic asymmetric unit contains two independent thymine molecules plus one partially occupied site for an ethyl acetate molecule. The two independent thymine molecules show similar geometrical features, except that the dimethoxytrityl groups adopt different orientations with respect to the remainder of the molecule. Each thymine base adopts an anti conformation with respect to the attached deoxyribose ring, and the deoxyribose rings show C3-endo puckering. The conformation of the side chain at the C1 position of the deoxyribose ring is gauche+. Intermolecular N-H···O and O-H···O hydrogen bonds link the molecules into one-dimensional chains.