The title compound, C(20)H(20)N(2)O(3), is a head-to-tail oxetane, one of the regioisomers obtained by the the Paternó-Büchi reaction of 1,3-dimethyl-thymine with benzophenone. The oxetane ring is folded, the dihedral angle between the C-O-C and C-C-C planes being 14.4 (2)°. The dihedral angle between the two phenyl rings is 64.3 (2)°. The pyrimidine ring adopts a boat conformation. The crystal structure involves weak C-H⋯O hydrogen bonds.