Abstract

Conformational polymorphism is observed in the inclusion crystals of cholic acid 1 with ethyl acetate. Direct recrystallization of host 1 from ethyl acetate gives one polymorph (monoclinic P2₁); in the presence of 1-naphthylmethylamine as a third component another polymorph (triclinic P1) is produced. The former has gauche conformation of the side chain (the dihedral angle of C17–C20–C22–C23, ψ⊕=⊕65°) while the latter has trans conformation (ψ⊕=⊕−158 and −168°), although they have similar bilayer host frameworks with the same 1∶1 host–guest stoichiometries. This results in differences between the hydrogen bond networks, the cavity shapes and the orientations of the guest molecules.