Abstract
In order to overcome some problems with 2D NMR, we have developed three NMR techniques, time sharing decoupling NOE (TSD-NOE), selective HOHAHA-CH and selective HOHAHA-COSY. TSD-NOE, which utilizes composite 90 degree pulse for observation and time sharing decoupling, enables to carry out 1D NOE experiments with extremely high selectivity. Selective HOHAHA-CH detects proton magnetization transferred from a specific proton by carbon-13 and is a very good technique to analyze congested methylene proton regions. Selective HOHAHA-COSY is a combination of HOHAHA and COSY and very powerful for analyzing complicated proton spin systems. These techniques has been applied for structural elucidation of a new antibiotic SS49 (C_<40>H_<68>O_<11>). SS49 is structurally related to cytovaricin and phthoramycin as shown in Fig. 11.
