Synthesis and Biotransformation of Plausible Biosynthetic Intermediates of Salicylaldehyde‐Type Phytotoxins of Rice Blast Fungus, Magnaporthe grisea

Abstract

Rice blast fungus, Magnaporthe grisea, produces a series of salicylaldehyde‐type phytotoxins such as pyriculol, pyricuol, and pyriculariol. Plausible biosynthetic intermediates of these phytotoxins were synthesized in deuterium labeled forms using the Stille coupling reaction as the key step, and subjected to biotransformation by the fungus. Heptatrienylsalicylaldehyde was converted into dihydropyriculol by the fungus by a shaking culture. A new biosynthetic pathway comprising both oxidation and reduction is proposed.

Unravelling the biosynthesis of pyriculol in the rice blast fungus Magnaporthe oryzae

“…The recently proposed biosynthesis process describes pyriculol as the intermediate product and the dihydro derivatives need the pyriculol molecule as a precursor [18]. That hypothesis could be underpinned with the results in our study concerning the correlation of heptaketide synthesis and MoPKS19 gene expression in axenic cultures of M. oryzae.…”

“…Metabolization of monosaccharides into mannitol and glycerol for carbon sequestration and osmolyte production was suggested to drive hyphal growth in planta [17]. Furthermore, a series of salicylaldehyde-type phytotoxins, such as pyriculol and pyriculariol, were found and putative biosynthetic intermediates of these compounds were synthesized to elucidate the biosynthesis [18]. However, no further studies have been published to date concerning the M. oryzae PKS gene cluster with respect to the biosynthesis of pyriculol and pyriculariol.…”

“…The culture fluid was separated from the mycelium by filtration and extracted with ethyl acetate (1 : 1, v/v) to yield 280 mg crude extract. Solidphase extraction (Chromabond C 18 ]. The following pyriculol derivatives were isolated: dihydropyriculariol (1.5 mg; retention time, 26.5 min), dihydropyriculol (3.4 mg; retention time, 27-27.5 min) and pyriculariol (7.3 mg; retention time, 48.5-49 min).…”

Synthetic studies of biologically active natural products contributing to pesticide development

“…3). [30][31][32][33][34][35] Through synthetic studies, it was clarified that the blast fungus produces optically active toxins such as pyriculol and pyricuol under shaking culture conditions, while pyriculariol and dihydropyriculariol resulting from aeration and agitation culture are racemic. 36) Pseudomonas syringae pv.…”

5-(2,2-Dimethyl-4H-1,3-benzodioxin)methanol: the synthetic precursor to o-formyl-m-hydroxycinnamic acid, the most oxidized salicylaldehyde-type phytotoxin isolated from rice blast fungus, Magnaporthe grisea

“…We have reported the synthesis of the derivatives 1-3, 5 using a common intermediate, 5-(2,2-dimethyl-4H-1,3-benzodioxin)methanol (7) (Scheme 2) [7][8][9][10]. In continuation of our synthetic studies of these compounds [7][8][9][10][11][12][13], the most oxidized derivative 6 was prepared for the first time from 7. Isolation and synthesis of o-carboxy-m-hydroxycinnamic acid, the related phytotoxin from other sources, has been reported [14][15][16].…”