Hidalgo José Ruiz, Neske Adriana, Iramain Maximiliano A, Alvarez Patricia E, Bongiorno Patricio Leyton, Brandán Silvia Antonia
UNT-FBQF-Argentina, Instituto de Química Orgánica, Tucumán, Argentina.
Cátedra de Química General, Instituto de Química Inorgánica, Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Ayacucho 471, 4000, San Miguel de Tucumán, Tucumán, Argentina.
J Mol Struct. 2020 Nov 5;1219:128610. doi: 10.1016/j.molstruc.2020.128610. Epub 2020 Jun 8.
Squamocin, an annonaceous acetogenin has been experimentally isolated and characterized in the solid state using the FT-IR and FT-Raman spectra and in methanol solution by UV-visible spectrum. The main bands observed were assigned combining the IR and Raman spectra with hybrid functional B3LYP/6-31G∗ calculations. Structural, electronic and topological properties were predicted at the same level of theory for the most stable conformer of squamocin in gas phase and methanol solution. A corrected solvation energy value of -147.54 kJ/mol was predicted for squamocin in methanol while the atomic population natural (NPA) charges evidence higher values on O atoms of R2 and R3 rings, as compared with the corresponding to lactone ring. Mapped MEP surfaces suggest that nucleophilic regions are located on the O atoms of three rings and of OH bonds belonging to side chain, in agreement with the higher charges values evidenced on these O atoms while electrophilic regions are predicted on the H atoms of OH groups. High stabilities of squamocin in both media was revealed by AIM studies while only in methanol solution by NBO calculations. The expansion of volume and the higher dipole moment in methanol suggest a clear solvation of squamocin by solvent molecules. Gap values have evidenced that squamocin is most reactive in methanol while that its large aliphatic chain produces an increases the reactivity of this γ-lactone, as compared with ascorbic acid lactone. Reasonable concordances among the predicted UV-visible and IR, Raman spectra with the corresponding experimental ones were found.
番荔枝辛，一种番荔枝科产的乙酰精，已通过傅里叶变换红外光谱（FT-IR）和傅里叶变换拉曼光谱在固态下进行了实验分离和表征，并通过紫外可见光谱在甲醇溶液中进行了表征。结合红外光谱和拉曼光谱以及杂化泛函B3LYP/6-31G∗计算对观察到的主要谱带进行了归属。在相同理论水平上预测了番荔枝辛在气相和甲醇溶液中最稳定构象体的结构、电子和拓扑性质。预测番荔枝辛在甲醇中的校正溶剂化能值为-147.54 kJ/mol，而自然原子布居（NPA）电荷表明，与内酯环对应的情况相比，R2和R3环的O原子上的值更高。映射的分子静电势（MEP）表面表明，亲核区域位于三个环的O原子以及属于侧链的OH键上，这与这些O原子上显示的较高电荷值一致，而亲电区域则预测在OH基团的H原子上。分子中的原子（AIM）研究表明番荔枝辛在两种介质中都具有高稳定性，而自然键轨道（NBO）计算仅表明在甲醇溶液中具有高稳定性。甲醇中体积的膨胀和较高的偶极矩表明溶剂分子对番荔枝辛有明显的溶剂化作用。能隙值表明番荔枝辛在甲醇中反应性最高，而与抗坏血酸内酯相比，其大的脂肪族链增加了这种γ-内酯的反应性。预测的紫外可见光谱以及红外光谱、拉曼光谱与相应的实验光谱之间存在合理的一致性。
