DEVELOPMENT OF NEW NMR TECHNIQUES AND THEIR APPLICATION TO STRUCTURAL ANALYSIS OF NATURAL PRODUCTS

在这个项目中，我们研究了我们小组开发的一种新的核磁共振技术，称为解耦- hmbc (D-HMBC)，用于复杂天然产物的结构分析。此外，我们还使用JEOL集团新开发的软件程序（MolSkop）通过计算机计算进行了立体结构分析。因此，D-HMBC已被证明是观测迄今为止无法探测到的小范围^<13>C-^1H耦合的一种极好的方法。此外，我们改进了数据处理程序；采用t2轴数据的相敏模式和t1轴数据的功率模式进行数据处理，得到了较好的核磁共振谱，信噪比有所提高。将D-HMBC与脉冲场梯度（PGF）技术进行比较，发现PFG在大多数情况下优于D-HMBC，但当信号强度受到^1H-^1H自旋耦合引起的j调制影响较大时，D-HMBC的效果更好，因此是这种情况下的首选方法。在本项目中，我们建立了获得良好的D-HMBC光谱的实验条件。这一技术已应用于市售核磁共振仪器，目前正被一些团体使用。我们改进了MolSkop软件程序，证明了它是一种分析复杂多环系统结构的有效方法。此外，我们最近开发了一种名为TANGO-D-HMBC的新技术，它对于检测由两个键分开的^<13>C-^<13>C耦合非常有用。这种^<13>C-^<13>C的长程耦合是用其他方法很难观测到的。该脉冲序列对于详细分析微生物产物碳骨架排列形成的^<13>C-标记模式非常有用。

In this project, we have investigated the applications of a new NMR technique called decoupled-HMBC (D-HMBC) developed by our group to structural analysis of complicated natural products. In addition, we have carried out analysis of stereo-structures by computer calculations using a newly developed software program (MolSkop) by the JEOL group.As a result, D-HMBC has turned out to be an excellent method to observe small long-range ^<13>C-^1H couplings, which can not be detected by hitherto available techniques. In addition, we have improved the data processing procedures ; ood NMR spectra with improved signal to noise ratio were obtained when data processing was made by the phase sensitive mode of the t2 axis data and by power mode of the t1 axis data.Comparison of this new technique (D-HMBC) with the pulse field gradiet (PGF) technique has revealed that PFG is superior to D-HMBC in most cases, but when the signal intensities were considerably affected by J-modulation caused by ^1H-^1H spin couplings, D-HMBC gave better results and so a method of choice in such situation. In this project, we have established experimental conditions for obtaining good D-HMBC spectra. This technique has been implemented to commercially available NMR instruments is now being used by some groups.We have improved the MolSkop software program and proved that it is a useful method to structural analysis of complicated polycyclic systems.In addition, we have recently developed a new technique called TANGO-D-HMBC,which is quite useful for detecting ^<13>C-^<13>C couplings separed by two bonds. Such kinds of long-range ^<13>C-^<13>C couplings were hardly observed by other methods. This pulse sequence is quite useful for datailed analysis of the ^<13>C- labeling pattern with microbial products formed by arrangement of the carbon skeleton.