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首页> 外文期刊>Crystal growth & design >Experimental and Computational Hydrate Screening: Cytosine, 5-Flucytosine, and Their Solid Solution
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Experimental and Computational Hydrate Screening: Cytosine, 5-Flucytosine, and Their Solid Solution

机译：实验和计算水合物筛选：胞嘧啶，5-氟藻胺及其固溶体

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摘要

The structural, temperature-, and moisture-dependent stability features of cytosine and 5-flucytosine monohydrates, two pharmaceutically important compounds, were rationalized using complementary experimental and computational approaches. Moisture sorption/desorption, water activity, thermal analysis, and calorimetry were applied to determine the stability ranges of hydrate <-> anhydrate systems, while X-ray diffraction, IR spectroscopy, and crystal structure prediction provided the molecular level understanding. At 25 degrees C, the critical water activity for the cytosine hydrate anhydrate system is similar to 0.43 and for 5-flucytosine similar to 0.41. In 5-flucytosine the water molecules are arranged in open channels; therefore, the kinetic desorption data, dehydration at < 40% relative humidity (RH), conform with the thermodynamic data, whereas for the cytosine isolated site hydrate dehydration was observed at RH < 15%. Peritectic dissociation temperatures of the hydrates were measured to be 97 and 84 degrees C for cytosine and 5-flucytosine, respectively, and the monohydrate to anhydrate transition enthalpies to be around 10 kJ mol(-1). Computed crystal energy landscapes not only revealed that the substitution of C5 (H or F) controls the packing and properties of cytosine/5-flucytosine solid forms but also have enabled the finding of a monohydrate solid solution of the two substances, which shows increased thermal- and moisture-dependent stability compared to 5-flucytosine monohydrate.
机译：胞嘧啶和5-氟藻胺一水合物的结构，温度和依赖性稳定性两种药学上重要的化合物，使用互补的实验和计算方法合理地合理化。施加湿度吸附/解吸，水活性，热分析和量热法以确定水合物 - 水合物系统的稳定范围，而X射线衍射，IR光谱和晶体结构预测提供了分子水平的理解。在25摄氏度下，胞嘧啶水合物余量系统的临界水活性类似于0.43和类似于0.41的5-氟藻。在5-氟纤维中，水分子布置在开放通道中;因此，动力学解吸数据，在<40％相对湿度（RH）下脱水，符合热力学数据，而对于胞嘧啶，分离的分离的位点在RH <15％时观察水合物脱水。将水合物的包层分离温度分别测量胞嘧啶和5-氟藻胺的97和84℃，并将一水合物与水合物过渡焓进行约10kJ摩尔（-1）。计算的晶体能量景观不仅揭示了C5（H或F）的取代控制了胞嘧啶/ 5-氟藻胺固体形式的填料和性质，但也使得能够发现两种物质的一水合物固溶体，其显示出增加的热量 - 与5-氟藻胺一水合物相比，依赖于水分依赖性稳定性。

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