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

The title compound, C₃₁H₃₂N₂O₇·0.25C₄H₈O₂, is a key inter­mediate in the synthesis of [¹⁸F]fluorine-labelled thymidine (¹⁸F-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.