`Guest-Free' Dianin's Compound

The existence of empty hour-glass-shaped cavities is confirmed for the crystal of the title compound, 4-(p-hydroxyphenyl)-2,2,4-trimethylchroman [systematic name: 4-(2,2,4-trimethylchroman-4-yl)phenol, C₁₈H₂₀O₂]. The structure of the cavities is essentially invariant when they intercalate guest molecules. The effects of the cage structure on ¹³C NMR chemical shifts of the methyl carbons are elucidated.