Walczak Dominik, Nowacki Andrzej, Trzybiński Damian, Samaszko-Fiertek Justyna, Myszka Henryk, Sikorski Artur, Liberek Beata
Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland.
Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; Biological and Chemical Research Centre, University of Warsaw, Żwirki i Wigury 101, 02-089 Warsaw, Poland.
Carbohydr Res. 2017 Jun 29;446-447:85-92. doi: 10.1016/j.carres.2017.05.011. Epub 2017 May 19.
N-(α-d-Glucofuranurono-6,3-lactone)-p-nitroaniline and N-(methyl β-d-glucopyranuronate)-p-nitroaniline were obtained as crystalline solids. The single-crystal X-ray diffraction, NMR data and DFT calculations for N-(α-d-glucofuranurono-6,3-lactone)-p-nitroaniline indicate that this N-furanoside adopts a T/E-like conformation in the crystal lattice, solution and gas phase. Thus, the structure of recorded for N-furanoside H NMR spectrum is indicative of the T/E region of the pseudorotational itinerary for furanose derivatives with α-d-gluco, β-L-ido and α-d-xylo configurations. Moreover, it is concluded that the T/E/T/E region of the pseudorotational itinerary for furanose derivatives with d-gluco, L-ido and d-xylo configurations should be characterised by the lack of coupling between H2 and H3 protons, irrespective of the anomeric configuration. Such a lack of vicinal coupling is characteristic for some of the trans-oriented furanose ring protons. The single-crystal X-ray diffraction and NMR data for N-(methyl β-d-glucopyranuronate)-p-nitroaniline indicate that this N-glucuronide adopts the C conformation, both in the crystal lattice and solution. The occurrence of anomeric effects in the presented N-glycosides is discussed. The crystal structure analysis of both N-glycosides gives evidence that the amine group in p-nitroaniline is planar due to the nitrogen sp hybridisation.
N-（α-D-呋喃葡萄糖醛酸-6,3-内酯）-对硝基苯胺和N-（甲基β-D-吡喃葡萄糖醛酸酯）-对硝基苯胺均以结晶固体形式获得。对N-（α-D-呋喃葡萄糖醛酸-6,3-内酯）-对硝基苯胺的单晶X射线衍射、核磁共振数据和密度泛函理论计算表明，这种N-呋喃糖苷在晶格、溶液和气相中采用类似T/E的构象。因此，记录的N-呋喃糖苷氢核磁共振谱的结构表明了具有α-D-葡萄糖、β-L-艾杜糖和α-D-木糖构型的呋喃糖衍生物假旋转行程的T/E区域。此外，得出结论，具有D-葡萄糖、L-艾杜糖和D-木糖构型的呋喃糖衍生物假旋转行程的T/E/T/E区域的特征应是H2和H3质子之间缺乏偶合，而与端基构型无关。这种邻位偶合的缺乏是一些反式取向的呋喃糖环质子的特征。N-（甲基β-D-吡喃葡萄糖醛酸酯）-对硝基苯胺的单晶X射线衍射和核磁共振数据表明，这种N-葡萄糖醛酸酯在晶格和溶液中均采用C构象。讨论了所呈现的N-糖苷中异头效应的发生情况。两种N-糖苷的晶体结构分析表明，由于氮的sp杂化，对硝基苯胺中的胺基是平面的。
