ABSTRACT

In order to overcome the problems such as low yield and complex products caused by direct esterification reaction of glutamic acid and cholesterol for the preparation of glutamic cholesterol ester (GCE), the new synthesis protocol was proposed. In this process, the amino of glutamic acid was first protected with a phthalimido group to produce followed N-phthaloyl-glutamic anhydride. Then, the glutamic anhydride was combined with cholesterol to form N-phthaloyl-glutamic cholesterol ester (NP-GCE). Finally, a de-protected GCE was obtained by hydrazine hydrate. The structures of GCE and NP-GCE were characterized by Fourier transform infrared spectra (FTIR), nuclear magnetic resonance spectrum (¹H and ¹³C NMR) and high-resolution mass spectra (HR-MS). The gelation properties of GCE and NP-GCE were evaluated in 15 solvents. The thermodynamic parameters of gels were studied by gel-sol transition temperature. The X-ray diffraction (XRD) was used to characterize the gelation mechanism and possible accumulation models of GCE. The results indicated that the new reaction route can eliminate the interference of amino group from glutamic acid, and the yield of GCE can reach 89.62 w%, which increased by 41.99 w% in comparison with the direct synthesis of glutamic acid and cholesterol. The gelling property demonstrated that GCE performs good gel properties in 5 solvents while NP-GCE only can from gel in 3 solvents. The gel-sol transition enthalpy of GCE is greater than that of NP-GCE, revealing the thermal stability of the gel from GCE is enhanced. XRD and SEM showed that GCE gel accumulated in lamellar structure due to the π-π stacking and hydrogen bond interactions.

摘要

为克服谷氨酸与胆固醇直接酯化反应制备谷氨酸胆固醇酯(GCE)的收率低、产物复杂等问题，提出了新的合成方案。在这个过程中，首先用邻苯二甲酰亚胺基保护谷氨酸的氨基，然后产生N-邻苯二甲酰谷氨酸酐。然后，谷氨酸酐与胆固醇结合形成N-邻苯二甲酰谷氨酸胆固醇酯（NP-GCE）。最后，通过水合肼获得去保护的GCE。GCE和NP-GCE的结构通过傅里叶变换红外光谱（FTIR）、核磁共振光谱（¹ H 和¹³C NMR）和高分辨率质谱（HR-MS）。GCE 和 NP-GCE 的凝胶化特性在 15 种溶剂中进行了评估。通过凝胶-溶胶转变温度研究凝胶的热力学参数。X射线衍射（XRD）用于表征GCE的凝胶机制和可能的积累模型。结果表明，新反应路线可以消除谷氨酸对氨基的干扰，GCE的收率可以达到89.62 w%，比直接合成谷氨酸和胆固醇提高了41.99 w%。凝胶性能表明 GCE 在 5 种溶剂中表现出良好的凝胶性能，而 NP-GCE 只能在 3 种溶剂中凝胶。GCE的凝胶-溶胶转变焓大于NP-GCE，表明GCE凝胶的热稳定性增强。