Raghavan K, Dwivedi A, Campbell G C, Johnston E, Levorse D, McCauley J, Hussain M
Du Pont Merck Pharmaceutical Co., Wilmington, Delaware 19880-0400.
Pharm Res. 1993 Jun;10(6):900-4. doi: 10.1023/a:1018973530443.
Losartan, an antihypertensive agent in clinical development, was found to exist in two enantiotropic polymorphic forms, a low-temperature stable form (Form I) and a high-temperature stable form (Form II), the temperatures at which they are stable being related to the transition temperature. X-ray powder diffraction patterns indicated differences in the crystal packing of the two forms. The vibrational data from infrared and Raman spectroscopy suggested a subtle change in molecular conformation and crystal packing in the two forms. Solid-state 13C NMR data of the polymorphs concurred with the vibrational data and indicated that, while the observed line widths reflect no major changes in crystallinity, signal multiplicities and chemical shifts do reflect differences in molecular packing in the respective unit cells. Thus, in the absence of crystallographic data, useful structural information could be derived from spectroscopic results to identify each of the crystalline forms.
氯沙坦是一种处于临床开发阶段的抗高血压药物，被发现以两种对映体多晶型形式存在，即低温稳定型（晶型I）和高温稳定型（晶型II），它们的稳定温度与转变温度相关。X射线粉末衍射图谱表明这两种晶型在晶体堆积方面存在差异。红外光谱和拉曼光谱的振动数据表明这两种晶型在分子构象和晶体堆积方面有细微变化。多晶型物的固态13C NMR数据与振动数据一致，表明虽然观察到的线宽并未反映出结晶度的重大变化，但信号多重性和化学位移确实反映了各自晶胞中分子堆积的差异。因此，在没有晶体学数据的情况下，可以从光谱结果中获得有用的结构信息来识别每种晶型。
