Aromatic triterpene tingenone

Dimers are a class of compounds isolated from only seven species of Celastraceae family [8,88]. These triterpene dimers were found to be composed of one quinoid type and one aromatic type of triterpene derived from pristimerin, tingenone and / or their congeners joined together by two ether linkages formed between the two A rings or between the A and B rings. From the methylene chloride soluble portion of a methanolic extract of Maytenus chuchuhuasca, four dimeric compounds were isolated by Shirota et al. [88]. 

Compounds (91), (92) and (93) had an identical molecular formula C58H74O8, which was established by HRFAB-MS. The NMR spectral data, which were similar to those of cangorosin B [7], suggested that each consisted of two different types of triterpene units, tingenone and pristimerin, one in the quinoid form and the other in the aromatic form. The stereochemistry was confirmed by means of ROES Y and CD spectral studies. The FAB-MS data enabled to determine whether the pristimerin and the tingenone type triterpene were in the quinoid form or in the aromatic form. Considering the spectroscopic evidences, the structures of (91), (92) and (93) were assigned to xuxuarines Fp, Ga and Gp respectively, Fig. (49). 

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