Roridin structure

Figure 1. Structures of roridins and baccharinoids (B1-B20) isolated from B. megapotamica.

Frequently, organisms will produce several members (factors) within a family of compounds. Product-ion MS/MS spectra can often be used to propose new structures within these series of natural product factors. For example, LC-MS/MS can provide both the molecular weight and product-ion MS/MS spectra of the unknowns. Database searches using these spectra may produce a match to a known natural product in the sample, which can be conlirmed as previously described. In addition, the correlation of product ions and neutral losses from the MS/MS spectra with the structure of these known compounds can often be used to propose structures for the other related factors in the sample. An example of this correlation was shown by Janota et al. [84], who used this approach to propose several structures within the roridin family. 

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. 

Satratoxins. A group of macrocyclic tric(h)othe-cenes formed by Stachybottys atra (newer name S. chartarum) and responsible for animal poisonings. S. are structurally closely related to the roridins and veiTucarins that are also produced by S. chartarum, a fungus growing especially on cellulose-containing substrates. 

A plausible sequence based on inspection of the structural formulae, and in which the roridin skeleton holds a central position, is shown in Scheme 6. The scheme assumes that the pathway in Baccharis, or its endophyte (see below), is essentially the same as in Myrothecium, and that all the fungal producers of macrocyclic trichothecenes use the same pathway. 

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... 

Of the eleven roridins isolated so far six have had their structures, with stereochemistry, determined. Although the basic skeleton of the roridins was established by Tamm 19) in 1966, the stereochemistry at C-6, C-13 ... 

Structure of roridin J, a new macrocyclic trichothecene from Myrothecium... 

Matsumoto, M., H. Minato, K. Tori, and M. Ueyama Structures of isororidin E, epoxyisororidin E, and epoxy- and diepoxyroridin H, new metabolites isolated from Cylindrocarpon species determined by carbon-13 and hydrogen-1 NMR spectroscopy. Revision of C-2 C-3 double bond configuration of the roridin group. Tetrahedron Letters 1977, 4093. 

The chief metabohte of most strains of Myrothecium verrucaria is the antibiotic verrucarin A, C27H34O9, for which structure I has been established by x-ray analysis (McPhail and Sim, 1965) and degradation (Gutzwiller and Tamm, 1965). Muconomycin A, isolated from the same source (Vittimberga, I963), appears to be identical to verrucarin A (Godtfredsen and Vangedal, 1965)-Verrucarin A (I), which is accompanied by related substances termed verru-carins and roridins, is the most abundant of these substances in M. verrucaria S 118, S 750 and S 833 it is found in M. roridum S 1135 but not in S 973 (Harri et al, 1962). 

FIGURE 49.8. Structures of eremantholide C, roridin A, verrucarin A, gorgonolide, ludartin, artemisin, and (+)-taxifolin. 

Several new compounds belonging to the roridin group have been isolated recently from a species of Cylindrocarpon. The structures of four of these metabolites, namely, 7jS,8jS-epoxyroridin H (41), 7j8,8)S,2, 3 -diepoxyroridin H (43), isororidin E (44), and 7j8,8j8-epoxyisororidin E (45) were elucidated (Matsumoto et al., 1977a,b) (Fig. 8). Other compounds, representing diesters of verrucarol, are vertisporin (42) (Minato et al, 1975) and satratoxin H (40) (Eppley and Bailey, 1973 Eppley et al., 1977) (Fig. 8). 

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