title: X-ray structural studies and physicochemical characterization of (E)-6-(3,4-dimethoxyphenyl)-1-ethyl-4-mesitylimino-3-methyl- 3,4-dihydro-2(1H)-pyrimidinone polymorphs.
abstract: The polymorphism of (E)-6-(3,4-dimethoxyphenyl)-1-ethyl-4-mesitylimino-3-methyl-3,4-di hydro- 2(1 H)-pyrimidinone (FK664; 1) was characterized by using X-ray powder diffractometry, differential scanning calorimetry (DSC), and IR spectroscopy. Structures of two polymorphs (Forms A and B) were determined by X-ray crystallographic analysis. Form A crystallized in the monoclinic space group P2(1)/c, with a = 13.504(2), b = 6.733(1), c = 24.910(8) A, beta = 96.55(4) degrees, z = 4, and dcal = 1.203 g/cm3, while Form B crystallized in the same space group, with a = 8.067(2), b = 15.128(4), c = 18.657(4) A, beta = 102.34(3) degrees, z = 4, and dcal = 1.216 g/cm3. The conformational features of 1 were very similar between the two polymorphs. Compound 1, in both crystal forms, took an energetically reasonable conformation in three rigid planes, such as 2-pyrimidone, trimethylphenyl, and dimethoxyphenyl rings, but the molecules were packed in different ways between the two polymorphs. In the Form B crystal, a short contact was possible, to form pi-pi interactions between two dimethoxyphenyl groups related with the inversion center in the crystal lattice; this interaction seems to contribute to stabilizing the crystal structure of Form B. Both Forms A and B showed only one endothermic peak due to fusion at 115 and 140 degrees C, respectively, on the DSC thermograms; therefore, it is suggested that there are no transition points between the two polymorphs. The heats of fusion obtained from the DSC thermograms were 33.2(2) kJ/mol for Form A and 36.8(1) kJ/mol for Form B.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Analytical Research Laboratory, Fujisawa Pharmaceutical Company, Ltd., Osaka, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Miyamae
authors.forename: S
authors.initials: S
authors.lastname: Kitamura
authors.forename: T
authors.initials: T
authors.lastname: Tada
authors.forename: S
authors.initials: S
authors.lastname: Koda
authors.forename: T
authors.initials: T
authors.lastname: Yasuda
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004055:Differential Thermal Analysis; D007536:Isomerism; D008968:Molecular Conformation; D011744:Pyrimidinones / Q000737:chemistry*; D012542:Scattering, Radiation; D013055:Spectrophotometry, Infrared; D014961:X-Ray Diffraction; D014965:X-Rays
chemical_list: D011744:Pyrimidinones; C062761:FK 664