论文部分内容阅读
近年来化学分离、精制技术有了显著的进步,天然有机化学所研究的对象是极其微量而又不稳定的生理活性物质,其中抗生素研究所面临的是最为复杂的天然产物。抗生素样品因量少使得不可能用化学分解法测定结构,而且常遇到样品结晶困难而无法用X一射线衍射法解析结构。在这种情况下,化学全结构解析的唯一方法是用核磁共振法。NMR谱在遇到质子信号重叠的情况下,解析结构非常困难,NMR质子信号重叠有以下两种:1)每个自旋偶合系统信号分辩较好,但各系统因化学位移相近而重叠。2)自旋偶合质子信号偶合分裂成多重峰,分辩很差。在1)情况下,可以用去偶差谱法(Decoupling Difference Spectroscopy),多量子滤过化学位移相关谱(Multiple Quantum Filter—COSY)等技术解决,但这些方法费时费力,只有偶合常数较大的质子自旋偶合才能得到良好的结果,显然满足不了对未知结构的解析要求。
In recent years, chemical separation and purification technology have made significant progress. Natural organic chemistry is the object of extremely trace and unstable physiological active substances, of which the antibiotic research is facing the most complex natural products. Due to the small quantity of antibiotic samples, it is not possible to determine the structure by chemical decomposition, and it is often difficult to crystallize the sample by X-ray diffraction. In this case, the only way to resolve the chemical structure is to use NMR. NMR spectra are very difficult to resolve in the case of proton signal overlap. NMR proton signals overlap in the following two ways: 1) The signals of each spin-coupled system are well resolved, but the systems overlap due to similar chemical shifts. 2) Spin-coupled proton signal coupling splits into multiple peaks with poor resolution. In the case of 1), the methods such as Decoupling Difference Spectroscopy and Multiple Quantum Filter-COZY can be used to solve these problems. However, these methods are time-consuming and labor-intensive, and only have large coupling constants Proton spin coupling to get good results, obviously can not meet the analytical requirements of the unknown structure.