Development and application of new NMR technique

虽然HMBC对于复杂分子的结构分析是一种非常有用的技术，但它有时会遇到以下问题。长延时(Delta)的建立必须考虑到长程^&lt；13&gt；C-^1H自旋耦合以及要观测到的质子的多重性。因此，如果长程耦合常数很小，或者质子作为一个很宽的信号，就不能探测到交叉峰。另外，强的t_1噪声伴随着尖锐的质子信号。我们现在提出了三种不同的应用技术，去耦合HMBC(D-HMBC)，3D-HMBC和Tango-HMBC。去耦合HMBC(D-HMBC)，3D-HMBC和Tango-HMBC方法在分析包括四元碳在内的复杂和/或重叠的质子自旋系统中是有用的。它们在复杂天然产物的结构研究中的应用表明，这些技术比HMBC方法有几个优点。

Although HMBC is a quite useful technique for structural analysis of complicated molecules, it is sometimes encountered with the following problem. Long delay time (DELTA) has to be set up by considering the long range ^<13>C-^1H spin couplings as well as multiplicity of the protons to be observed. Thus the corss peaks can't be detected if the long range ^<13>C-^1H coupling constant is very small, or if the proton appers as a very broad signal. In addition, strong t_1 noises appear with sharp proton signals.We now propose three different application techniques, decoupled-HMBC (D-HMBC), 3D-HMBC and TANGO-HMBC.Decoupled-HMBC (D-HMBC), 3D-HMBC and TANGO-HMBCmethods are useful in analyzing the complicated and/or overlapped proton spin systems including quaternary carbons. Their applications to structural studies of complicated natural products have shown several advantages of these techuniques over the HMBC method.