抄録
In order to overcome the problems of a widely used NMR technique, HMBC, we have developed a new technique named decoupled-HMBC (D-HMBC) which enables to observe ^1H-^<13>C long-range coupling separated by four or five bonds with small coupling constants (J<2Hz). Its application for structural studies of a new peptide, SF2741B, and a macrolide antibiotic, monazomycin are described. In addition, two new NMR techniques, HMBC-COSY and HMBC-HOHAHA, which are combinations of HMBC and COSY, or HMBC and HOHAHA pulse sequences, are proposed. These methods enable to reveal complicated and/or overlapped proton spin systems, which are often difficult to analyze by conventional techniques including HMBC. Their applications to structural studies of complicated natural products showed several advantage of these techniques over the HMBC method.
