Study on four polymorphs of bifendate based on X-ray crystallography

Jinju Nie; Dezhi Yang; Kun Hu; Yang Lu

doi:10.1016/j.apsb.2016.03.006

Study on four polymorphs of bifendate based on X-ray crystallography

Acta Pharm Sin B. 2016 May;6(3):234-42. doi: 10.1016/j.apsb.2016.03.006. Epub 2016 Apr 13.

Authors

Jinju Nie¹, Dezhi Yang¹, Kun Hu¹, Yang Lu¹

Affiliation

¹ Beijing City Key Laboratory of Polymorphic Drugs, Center of Pharmaceutical Polymorphs, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.

Abstract

Bifendate, a synthetic anti-hepatitis drug, exhibits polycrystalline mode phenomena with 2 polymorphs reported (forms A and B). Single crystals of the known crystalline form B and 3 new crystallosolvates involving bifendate solvated with tetrahydrofuran (C), dioxane (D), and pyridine (E) in a stoichiometric ratio of 1:1 were obtained and characterized by X-ray crystallography, thermal analysis, and Fourier transform infrared (FT-IR) spectroscopy. The differences in molecular conformation, intermolecular interaction and crystal packing arrangement for the four polymorphs were determined and the basis for the polymorphisms was investigated. The rotation of single bonds resulted in different orientations for the biphenyl, methyl ester and methoxyl groups. All guest solvent molecules interacted with the host molecule via an interesting intercalative mode along the [1 0 0] direction in the channel formed by the host molecules through weak aromatic stacking interactions or non-classical hydrogen bonds, of which the volume and planarity played an important role in the intercalation of the host with the guest. The incorporation of solvent-augmented rotation of the C-C bond of the biphenyl group had a striking effect on the host molecular conformation and contributed to the formation of bifendate polymorphs. Moreover, the simulated powder X-ray diffraction (PXRD) patterns for each form were calculated on the basis of the single-crystal data and proved to be unique. The single-crystal structures of the four crystalline forms are reported in this paper.

Keywords: ADPs, anisotropic displacement parameters; ALT, alanine transaminase; Bifendate; CCDC, Cambridge crystallographic data center; DDB, dimethyl dimethoxy biphenyl dicarboxylate; DSC, differential scanning calorimetry; FT-IR; FT-IR, Fourier transform infrared spectroscopy; MW, molecular weight; PXRD, powder X-ray diffraction; Polymorphism; SCXRD, single-crystal X-ray diffraction; Single-crystal structure; Solvatomorphism; TGA, thermal gravimetric analyzer.; Thermal analysis.