NMR determination of the structure of Julibroside J
1996
Ma, L. | Tu, G. | Chen, S. | Zhang, R. | Lai, L. | Xu, X. | Tang, Y.
Julibroside J(1) is a new triterpenoid saponin which contains one triterpene, two monoterpenes and nine sugar residues. The structure has been determined almost exclusively by high-resolution NMR methods. The (1)H and (13)C NMR spectra of Julibroside J(1) C(5)D(5)N have been assigned by homonuclear and heteronuclear and heteronuclear correlation experiments, such as COSY, CH-COSY, TOCSY, HMBC, HMQC-COSY, HMQC-TOCSY and NOESY. Anomeric configurations were obtained by combined use of (1)J(CH) and (3)J(H1.H2) and NOESY data. The particular sugar residues were identified by utilizing (3)J(HH) values obtained from TOCSY cross-peaks, NOE difference spectra, and several 1D-TOCSY spectra, and three-bond intra-ring cross-peaks from a HMBC spectrum. Linkage assignments were made using the HMBC spectrum, and supplemented by NOE data from the NOESY spectrum. The structure of Julibroside J(1) was characterized as 3-O-[beta-D-xylopyranosyl-(1 leads to 2)-alpha-L-arabinopyranosyl-(1 leads to 6)-beta-D-glucopyranosyl]-21-O-((6S)-2-trans-2-hydroxymethyl-6-methyl-6-O-[4-O-((6S)-2-trans-2,6-dimethyl-6-O-(6-deoxy-beta-D-glucopyranosyl)-2,7-octadienoyl)-6-deoxy-beta-D-glucopyranosyl]-2,7-octadienoyl)-acacic acid 28-O-(beta-D-glucopyranosyl-(1 leads to 3)-[alpha-L-arabinofuranosyl-(1 leads to 4)]-alpha-L-rhamnopyranosyl-(1 leads to 2))-beta-D-glucopyranosyl ester.
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