Rice blast disease

During the synthesis of a new rice blast disease fungicide, the 5-hydroxy-l,2,4-oxadiazole 90 underwent reaction on the 4-nitrogen to furnish the 4-substituted-l,2,4-oxadiazol-5-one 91 as shown in Equation (8) <2002JPES221>. 

With respect to five-membered lactones fused to hexopyranose units, some approaches have been reported so far and the exploitation of their synthetic potential has led to the access of new carbohydrate derivatives. Bicyclic derivatives of this type are key intermediates in the synthesis of the epimer at C-3 of the sugar moiety contained in miharamycins [212, 213]. The latter are antibiotics known to inhibit strongly Pyricularia oryzae, which produces the rice blast disease. These compounds are also considered to be a potential bioterrorism agent (Scheme 42). Hence, the 3,3-spiroepoxide 176 was converted into the 3-C-cyanomethyl derivative 177, the hydrolysis of which led to spontaneous cyclization in the presence of... 

Kato, T., Yamaguchi, Y., Hirano, T., Yokoyama, T., Uyehara, T., Namai, T., Yamanaka, S., and Harada,N. 1984. Unsaturated Hydroxy Fatty-Acids, the Self Defensive Substances in Rice Plant against Rice Blast Disease. Chem. Lett., 409-412. 

Unsaturated hydroxy fatty acids, the self-defensive substances in rice plant against Rice Blast Disease. Chem. Lett., 25, 409 112. 

Structure and synthesis of unsaturated trihydroxy c18 fatty acids in rice plant suffering from Rice Blast Disease. Tetrahedron Lett., 26, 2357-2360. 

Kato, T., Yamaguchi, Y., Ohnuma, S. I., Uyehar, T., Nmai, T., Kodama, M., and Shibara, Y. 1986. Structure and synthesis of ll,12,13-trihydroxy-9Z,15Z-octadecadienoic acids from rice plant suffering from rice blast disease. Chem. Lett.,27,577-580. 

Tamari, K. Ogasawara, N. Kaji, J. In "The Rice Blast Disease" Johns Hopkins Baltimore 1965 p. 35. 

Development of ethylene [64] starts about 40-60 min after mechanical perturbation, much earlier than generation of salicylic acid [53]. This perturbation is induced, for instance, just by wind [30], explaining the observation that the rice blast disease (induced by pathogens) is suppressed in seasons of strong wind (apparently the perturbation induces expression of ethylene, this stimulates generation of phytoalexins which prevent attack by fungi). 

T. Kato, Y. Yamaguchi, T. Hirano, T. Yokoyama, T. Uyehara, T. Namai, S. Yamanaka, N. Harada, Unsaturated hydroxyl fatty acids, the self defensive substances in rice plant against rice blast disease, Chem. Lett. 26 (1984) 409. 

In the rice plant infected with the rice blast disease fungus, two dlterpene phytoalexins, momllactones A and B, were recorded in 1981 (39). These two substances incidentally also occur constitu-tlvely in the husks of the same plant. More recently in 1984, three further dlterpene phytoalexins have been described oryzalexins A, B and C (40). Structurally, these are sandaracopimaradlene derivati-... 

USE Antifungal against rice blast disease in Japan. 

The ability of several oxygenated Cig fatty acids, such as 174 and 177, isolated from rice plants (including Fukuyuki) suffering from rice-blast disease, to act as self-defense substances against the fungus, has attractive synthetic interest. Zinc-mediated addition of propargyl bromide to (S,S)A61 provides (iS)-173, which is converted in nine steps to (11 S, 12 S, 135)-trihydroxy-(9Z,15Z)-octadecadienoic acid (174) [67]. 

Melanin Biosynthesis Inhibitors. Among the most desirable targets for selective fungitoxic action are those uniquely associated with fungal pathogenicity such as the polyketide pathway to melanin in the fungus Pyricularia oryzae which causes rice blast disease. 

In that period after World War II, Japan citizens also suffered from shortages of food, especially rice. So as to increase the rice production, synthetic pesticides were used extensively in Japan. For example, parathion was used to control the Asiatic rice borer, Chilo suppressalis. Unfortunately, this phosphorus insecticide was highly toxic, and a number of farmers were killed by poisoning. Another notorious pesticide was phenylmercuric acetate, which was used against rice blast disease. Because it contained mercury, the public could not accept it. 

Blasticidin S (327) is an antifungal agent used against rice blast disease in Japan. It was isolated in 1958 from Streptomyces griseochromogenes [411] and the structure and absolute stereochemistry were elucidated by chemical means [412-415] and confirmed by X-ray spectroscopy [416,417]. The biosynthesis has also been determined [418,419]. 

---