9-(2,4-Di-fluoro-phen-yl)-3,3,6,6-tetra-methyl-3,4,5,6,7,9-hexa-hydro-2H-xanthene-1,8-dione.

In the title compound, C23H24F2O3, the central pyran ring has a flat-boat conformation, whereas the two fused cyclo-hexenone rings adopt envelope conformations, with the C atom bearing the dimethyl substituent being the flap atom in each case. The pyran ring mean plane and the di-fluoro-phenyl ring are almost normal to each other, making a dihedral angle of 87.55 (4)°. In the crystal, mol-ecules are linked by pairs of C-H⋯O hydrogen bonds, forming inversion dimers with an R 2 (2)(8) ring motif. The F atom at position 2 on the di-fluoro-phenyl ring is disordered over the 2- and 6-positions, and has a refined occupancy ratio of 0.932 (3):0.068 (3).

3,3,5,5-Tetra-methyl-r-2,c-6-diphenyl-piperidin-4-one.

The piperidone ring of the title compound, C(21)H(25)NO, adopts a chair conformation with the two phenyl groups equatorially oriented and cis to each other. In the crystal, mol-ecules are linked by weak N-H⋯O hydrogen bonds, forming chains parallel to [100].