The structure and sequence of a new HC-toxin analog 3 produced by H. carbonum is reported.The cyclic tetrapeptide HC-toxin-1 1, elaborated by the fungus H. carbonum shows host-specific toxicity toward susceptible strains of maize.3In addition to two units of alanine and one proline moiety, this toxin contains the unusual amino acid, 2- amino-8-0x0-9,lO-epoxydecanoic acid (Aoe) which has also been found in other bioactive fungal metabolites.3-6We have examined culture filtrates of H. carbonurn7 and have isolated two additional toxic cyclic tetrapeptides; the previously isolated HC-toxin-ll 26 with a glycine in place of one alanine unit; and HC-toxin-Ill 3 7 in which the proline of 1 is replaced by trans-3-hydroxyproline.The isolation and purification of the HC-toxins was accomplished as previously described.6From a 10-20L harvest of culture filtrate, we were typically able to obtain 0.480 grams o f 1 , 4.0 mg of 2 .and 2.4 mg of HC-toxin-Ill 3 in a chromatographically pure state.The purified toxins exhibited similar levels of toxicity.7 -&q0 0 R,=Me R,=H R2=H R2 = H HC-Toxin-l 1 HC-Toxin-ll 2 05-R1 =Me R2 = OH HC-Toxin-Ill 3
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Tanis et al. (1986) studied this question.