Wang S L, Lin S Y, Chen T F, Chuang C H
Biopharmaceutics Laboratory, Department of Medical Research & Education, Veterans General Hospital-Taipei, Shih-Pai, Taipei, Taiwan, Republic of China.
J Pharm Sci. 2001 Aug;90(8):1034-9. doi: 10.1002/jps.1056.
Thermal Fourier transform infrared (FT-IR) microspectroscopy was used to investigate the conformational isomerization of captopril in the solid state. The result indicates that the IR peak intensity of captopril for original bands decreased dramatically at 102 degrees C, but for new bands it increased with the rise of temperature. The frequency of C=O stretching mode for carboxylic acid and for amide was located at a higher wavenumber of 1747 cm(-1) and at a lower frequency of 1591 cm(-1) as compared with the general compound, suggesting the existence of trans isomer of captopril in the solid state by intramolecular hydrogen bonding. Beyond 102 degrees C, several new bands at 1720, 1645, and 1610 cm(-1) were observed with the rise of temperature, indicating the coexistence of a cis isomer. However, the cis isomer could transform gradually to the trans isomer after cooling. The thermodynamics of equilibrium mixture of cis/trans isomers were also studied. The trans isomer was more stable than the cis isomer, but the cis isomer was favored at the higher temperature.
采用热傅里叶变换红外（FT-IR）显微光谱法研究了卡托普利在固态下的构象异构化。结果表明，卡托普利原始谱带的红外峰强度在102℃时急剧下降，但新谱带的红外峰强度随温度升高而增加。与一般化合物相比，羧酸和酰胺的C=O伸缩振动模式频率分别位于较高波数1747 cm⁻¹和较低频率1591 cm⁻¹处，表明固态卡托普利通过分子内氢键存在反式异构体。超过102℃后，随着温度升高，在1720、1645和1610 cm⁻¹处观察到几个新谱带，表明存在顺式异构体。然而，冷却后顺式异构体会逐渐转化为反式异构体。还研究了顺式/反式异构体平衡混合物的热力学。反式异构体比顺式异构体更稳定，但顺式异构体在较高温度下更有利。
