Triptohypol NOESY experiment

The study of the outer root bark of T. hypoglaucum collected in China afforded three new structures of phenolic triterpenes. Duan et al. isolated triptohypol A (80), B (81) and C (82), a series of new phenolic compounds related to celastrol [29]. Triptohypol A (80) was isolated as an amorphous powder and spectroscopic means and chemical modification determined its structure. By HREIMS the formula C30H40O6 was determined, and H-NMR spectrum showed five methyl signals, a methoxy moiety, a methylene attached to an oxygen atom and two vinyl protons. Data from 13C-NMR experiments indicated the presence of a pair of carbonyl groups and was quite similar to that of wilforol A (78). The analysis of HMQC and HMBC experiments allowed to establish the structure for rings A and B, based on the correlations observed between the proton H-l (8 6.95 ppm) and the carbons C-3, C-5 and C-10. Finally, the position of the carbonyl group was established at C-6 based on a NOESY experiment of the dimethyl derivative. 

Triptohypol B (81) evidenced a very similar 13C-NMR spectrum when compared to triptohypol A, except for the replacement of a methylene carbon by a methyl carbon, which was supported by the formula CsoHLioOs, determined by HREIMS. A NOESY experiment indicated the correlation between the methyl proton signal with that of the C-3 methoxy group, which allowed to establish the structure of triptohypol B (81). 

Triptohypol F (18) showed the presence of one double bond, two methine carbons attached to an oxygen function and one methoxy group, according to the 13C NMR spectrum. From these data and its H NMR and MS spectra, it was assumed to be an oleanane-type triterpene. The location of the double bond and the hydroxyl and methoxy groups were determined by a HMBC experiment. The stereochemistry of the hydroxyl and methoxy groups were determined by a NOESY spectrum. According to these data the structure of (18) was established as showed above. 

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