J. M. Daly

Analogs of host-specific phytotoxin produced by Helminthosporium maydis, race T: I. Synthesis

Abstract Fourteen analogs of the host-specific corn phytotoxin (T toxin) obtained from cultures of the fungal plant pathogen, Helminthosporium maydis, race T, were synthesized. Addition of difunctional Grignard reagents to aldehyde intermediates resulted in shorter versions (C15–C26) of native toxin (C35–C45), containing the β-polyketol functions which appear to account for the specificity and very high toxicity (10−8–10−9 M) of T toxin toward certain corn varieties.

Analogs of host-specific phytotoxin produced by Helminthosporium maydis, race T: II. Biological activities

Abstract Inhibition of dark CO2 fixation by susceptible corn leaves was used to compare the relative toxicity of synthetic analogs with that of the host-specific phytotoxin produced by the fungal corn pathogen, Helminthosporium maydis, race T. Analogs with C15, C25, or C26 chain lengths and 1,5-dioxo-3-hydroxy functions were only slightly less toxic (2–6 × 10−7 M) than native T toxin (C35–C45 chain lengths) or its individual components (3 × 10−8 M). Like native toxin, analogs were host-specific in that they did not inhibit dark CO2 fixation in leaf tissue of resistant corn at concentrations 102–103 times greater than those effective with susceptible corn. These findings support the structures previously proposed for native T toxin.