Candibirin A,a furano­coumarin dimer isolated from Heracleum candicans Wall.

Candibirin A [systematic name: 9,9′‐(1,4‐dioxane‐2,5‐diyldi­methyl­ene­dioxy)­di(7H‐furo­[3,2‐g]­chromen‐7‐one)], a new furano­coumarin dimer, was isolated from Heracleum candicans Wall . ¹H NMR and MS spectra had indicated that the title compound was a dimer of heraclenin or heraclenol, but the linkage structure and its chirality were undetermined. The dioxane linkage, having the R,R configuration, has now been elucidated from di­methyl sulfoxide‐solvated crystals, C₃₂H₂₈O₁₀·2C₂H₆OS. Candibirin A is thus a dimerization product from heraclenin formed by reaction at the epoxy group. Di­methyl­form­amide‐solvated crystals, C₃₂H₂₈O₁₀·C₃H₇NO, adopt a different conformation, with a folded structure that differs from the extended structure in the dimethyl sulfoxide solvate. However, the puckering of the dioxane linker unit is very similar in the two conformers. This result shows that the rotation of the ether bonds, in the linker between the furano­coumarin and dioxane moieties, causes the conformational flexibility of (I).