Baccharin structure

Structural comparison of the isolated compounds with spectral data in the literature identified them as drupanin, kaempferide, artepillin C, and baccharin [18, 19, 20, 21], The structures of the four compounds are shown in Figure 1 and Supplementary Figures 1-5. 

The roridin family constitutes another subclass of the trichothecane macrolides. Two examples of this group are roridin E (148) and baccharin Bj (150). The latter is isolated from the plant Baccharis megapotamica and is a potent antileukemic agent. Structurally, this class of compounds is quite similar to the verrucarins discussed above, with the exception of the replacement of the hydroxypentanoic acid-muconic ester linkage by an ether bond and some additional carbon substitution. 

In the second structural group, the macrocyclic trichothecenes, the hydroxy groups at C-4 and C-15 of the simple trichothecene skeleton are bridged by a di- or trilactide ribbon. The verrucarins (triesters. Table IV), the roridins (diesters. Table V) and the baccharins (diesters. Table VI) are the major structural subunits of this group. Vertisporin and the satratoxins complete this class, and can be found at the bottom of Table V. Verrucarol (82) is most often the sesquiterpene onto which the macrocycle is attached. Verrucarin K (43) is a notable exception and was the first trichothecene known which lacks the 12,13-epoxide unit. A number of macrocyclic... 

Very recently, the isolation and structure elucidation of baccharin (47), an antileukemic trichothecene triepoxide, from Baccharis megapotamica Spreng (Asteraceae) was reported (Kupchan et al, 1976). This constitutes the first known case of a trichothecene derivative in higher plants. The full structure and stereochemistry of baccharin (47) were established by X-ray analysis. 

---