Department of Organic and Analytical Chemistry, Institute of Nonferrous Metals and Materials Science, Siberian Federal University, pr. Svobodny 79, 660041 Krasnoyarsk, Russia.
Institute of Chemistry and Chemical Technology, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Akademgorodok, 50, bld. 24, 660036 Krasnoyarsk, Russia.
Int J Mol Sci. 2022 Jan 29;23(3):1602. doi: 10.3390/ijms23031602.
Betulin is an important triterpenoid substance isolated from birch bark, which, together with its sulfates, exhibits important bioactive properties. We report on a newly developed method of betulin sulfation with sulfamic acid in pyridine in the presence of an Amberlyst15 solid acid catalyst. It has been shown that this catalyst remains stable when being repeatedly (up to four cycles) used and ensures obtaining of sulfated betulin with a sulfur content of ~10%. The introduction of the sulfate group into the betulin molecule has been proven by Fourier-transform infrared, ultraviolet-visible, and nuclear magnetic resonance spectroscopy. The Fourier-transform infrared (FTIR) spectra contain absorption bands at 1249 and 835-841 cm; in the UV spectra, the peak intensity decreases; and, in the nuclear magnetic resonance (NMR) spectra, of betulin disulfate, carbons С3 and С28 are completely shifted to the weak-field region (to 88.21 and 67.32 ppm, respectively) with respect to betulin. Using the potentiometric titration method, the product of acidity constants K and K of a solution of the betulin disulfate H form has been found to be 3.86 × 10 ± 0.004. It has been demonstrated by the thermal analysis that betulin and the betulin disulfate sodium salt are stable at temperatures of up to 240 and 220 °C, respectively. The density functional theory method has been used to obtain data on the most stable conformations, molecular electrostatic potential, frontier molecular orbitals, and mulliken atomic charges of betulin and betulin disulfate and to calculate the spectral characteristics of initial and sulfated betulin, which agree well with the experimental data.
桦木醇是一种从桦树皮中分离得到的重要三萜类物质，其硫酸盐及其衍生物具有重要的生物活性。我们报道了一种在 Amberlyst15 固体酸催化剂存在下，用硫酸在吡啶中对桦木醇进行磺化的新方法。结果表明，该催化剂在反复使用（多达 4 次）时仍然稳定，并能确保获得含硫量约为 10%的磺化桦木醇。通过傅里叶变换红外、紫外可见和核磁共振波谱证明了桦木醇分子中引入了硫酸基。傅里叶变换红外（FTIR）光谱在 1249 和 835-841 cm 处有吸收带；在紫外光谱中，峰强度降低；在核磁共振（NMR）光谱中，桦木醇二硫酸盐的 C3 和 C28 碳原子完全移至弱场区域（分别为 88.21 和 67.32 ppm）相对于桦木醇。通过电位滴定法，发现桦木醇二磺酸钠 H 形式溶液的酸度常数 K 和 K 的乘积为 3.86×10±0.004。热分析表明，桦木醇和桦木醇二磺酸钠盐在高达 240 和 220°C 的温度下稳定。使用密度泛函理论方法获得了桦木醇和桦木醇二硫酸盐的最稳定构象、分子静电势、前沿分子轨道和 Mulliken 原子电荷的数据，并计算了初始和磺化桦木醇的光谱特性，与实验数据吻合良好。
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