In the title compound, C22H21N3O5, the β-lactam (azetidin-2-one) ring is nearly planar [maximum deviation = 0.010 (1) Å] and makes dihedral angles of 69.22 (5), 55.32 (5) and 89.42 (4)° with the least-squares planes formed by the four C atoms of the morpholine ring, which adopts a chair conformation, the benzene ring and the xanthene ring system, respectively. In the crystal, C-H⋯O hydrogen-bond contacts connect neighbouring mol-ecules into infinite zigzag chains running parallel to the b axis.