Polymorphism of R‑Encenicline Hydrochloride: Access to the Highest Number of Structurally Characterized Polymorphs Using Desolvation of Various Solvates

In a study of the solid form landscape of R-encenicline hydrochloride (Enc-HCl), it was found that this compound is dodecamorphic and presents the first published example of polymorphism with a record-breaking 10 solved crystal structures. In addition to the four known polymorphs, eighth new polymorphs and their precursor solvates as well as several new hydrates have been characterized. The polymorph formation behavior is investigated by analyzing crystal structures of polymorphs and solvates used in their preparation. Molecular packing in crystal structures of the polymorphs is highly similar to that in the precursor solvates, whereas conformations in all structures are nearly identical and correspond to the same energy minimum.