Abstract: The ¹³Cand ¹Hchemical shifts of ponicidin, which is one of antineoplastic and antiseptic effective components isolated from Rabdosia rvbescens (Hemsl.) Hara, were completely assigned by het-eronuclear chemical shift correlation spectroscopy, long-range heteronuclear chemical shift correlation spectroscopy (COLOC-S) and homonuclear chemical shift correlation spectroscopy.Since the BIRDand TANGOpulse sandwich in COLOC-Spulse sequence were used to suppress effectively the one-bond cross peaks and decouple the modulation of long-range cross peak intensities due to the one bond couplings, the most three-bond ¹³C-¹Hinteraction in ponicidin were dectected simultaneously in one COLOC-Sspectrum, and some four-bond cross peaks were also observed in the same spectrum.After carefully analyzing the ¹³Cand ¹Hchemical shift data, the XHCRcross peaks at 3.790/72.06, 4.196/72.98 and 5.010/69.79 ppm were deduced as the cross peaks of methylene carbon atoms directly bonded to oxygen, the long-range ¹³C--¹Hcross peaks in COLOC-Sspectrum confirmed that the ¹³Cresonance signals at 72.06, 72.98 and 69.79 ppm were assigned to Cl, C₆ and C14 methylene group, and the corresponding₁Hchemical shifts were 3.790, 4.196 and 5.010 ppm, respectively.The chemical shift assignments of other ¹³C Hresonance signals were completed by combining the COLOC-Sspectrum with hetero- and homo-nuclear correlation spectra.The 1Hresonance signals of two methyl group geminated at C₄ carbon atom were identified unequivocally with the cross peaks in NOESYspectrum.The results show that the 2D NMRmethods are very useful for the structure elucidation and spectral assignments of natural organic compounds, and the reliable structure parameters could be provided for calculating the three dimensional structures of ponicidin in solution.

Key words: 2D NMR, Spectral assignments, COLOC-S, Ponicidin