Application studies on vibrational circular dichroism as the chiroptical tool

碳水化合物的结构研究需要开发分析工具。VCD光谱具有潜在的用途，但与蛋白质和核酸相比，其对碳水化合物的应用受到限制，部分原因是光谱解释的困难。通过系统的碳水化合物测量，我们已经发现在1145 cm 2附近出现<-1>了轴向糖苷糖特征的强VCD峰，即糖苷带。同位素取代表明，深刻参与的异头部分的振动，这条带。为了通过密度泛函理论（DFT）计算预测其振动模式，制备了适当设计的模型化合物，并将它们的计算光谱与观测光谱进行了比较。在这项研究中，第一次，碳水化合物VCD光谱可靠地预测。此外，糖苷带的符号不仅反映了异头构型，而且也反映了吡喃糖构型。 ...更多信息 - 是的各向同性和理论研究将其振动模式表征为C1-H1变形与C1-O 1伸缩耦合，这表明其适用于更复杂的糖缀合物。最后，首次将VCD技术应用于糖肽，实现了糖和聚糖的同时分析，并首次对识别相关的独特糖N-乙酰神经氨酸（Neu 5Ac）进行了系统的VCD研究。合成了Neu 5Ac衍生物的两对C2不对称季碳端基异构体。VCD技术的其他应用也应用于生物活性化合物，如手性十字花科植物抗毒素和抗蛇毒的解毒剂样化合物（（+）-交替胺），借助DFT理论计算，在溶液中成功地归属了它们的立体化学。少

Structural studies of carbohydrates have required development of analytical tools. VCD spectroscopy has been of potential use, but its application to carbohydrates has been limited compared to proteins and nucleic acids partly due to the difficulties in the interpretation of the spectra. Through the systematical carbohydrate measurements, we have found an intense VCD peak appeared around 1145 cm^<-1> characteristic for axial glycosidic sugars i.e. the glycoside band. Isotope substitution indicated the profound participation of the anomeric moiety in the vibration of this band. To predict its vibrational mode by means of density functional theory (DFT) calculation, properly designed model compounds were prepared and their calculated spectra were compared with the observed ones. In this study, for the first time, carbohydrate VCD spectra were reliably predicted. Furthermore, the sign of the glycoside band was found to reflect not only the anomeric configuration but also the pyranose conf … More ormation. The isotropic and theoretical studies characterized its vibrational mode as the C1-H1 deformation coupled with C1-O1 stretching, which indicated the applicability to more complicated glycoconjugates. Finally, VCD technique was first applied to glycopeptides, and demonstrated the simultaneous analysis on both the carbohydrate and aglycan parts.Systematic VCD studies of N-acetylneuraminic acid (Neu5Ac), a recognition related unique carbohydrate, were performed for the first time. Two pairs of anomeric isomers regarding a quaternary C2 asymmetric carbon of Neu5Ac derivatives were synthesized. VCD spectral patterns around the ester carbonyl region, as well as other Mid-IR regions would be practical markers to distinguish the C2 stereochemistry.Other applications of the VCD technique were also applied to biologically active compounds such as chiral cruciferous phytoalexins and the antidote like compound against snake venom ((+)-alternamin), leading to successful assignments of their stereochemistries in solution station with the aids of their DFT theoretical calculations. Less