Crystal structure of 5,9-Dimethoxy-3,3,8-trimethy1-7,10-dihydro-3H-naphtho[ 2,1-b]pyran-7,10-dione

The crystal structure of the title compound, C₁₈H₁₈O₅, has been determined by single-crystal X-ray diffraction methods at 295 K and refined by least squares to a residual of 0•058 for 1502 ‘observed’ reflections. Crystals are monoclinic, P2₁/n, a 22•048(6), b 7•075(2), c 10•443(3) Å, β 100•40(3)°, Z 4. The structure was solved by a combination of special direct phasing procedures and translation functions, after conventional direct methods had failed.