Tadahiro Kato

Oxygenated Fatty Acids with Anti-rice Blast Fungus Activity in Rice Plants

Expecting that the different characteristics of rice plants against rice blast fungus, that is, susceptibility of the weaker cultivar, Sasanishiki and resistance of the stronger cultivars, Fukuyuki and Fukunishiki, may be due to the absence or presence of anti-fungus compounds in the rice plants, the anti-rice blast fungus substances in these three kinds of rice plants were explored. We found five epoxides and five allyl alcohols as anti-rice blast fungus compounds. The epoxides were 12,13-epoxy- and 9,10-epoxylinoleic acids, and 15,16-epoxy-, 12,13-epoxy-, and 9,10-epoxylinolenic acids. The allyl alcohols are 13-hydroxy and 9-hydroxy linoleic acids, and 16-hydroxy, 13-hydroxy, and 9-hydroxy linolenic acids. In inoculated Sasanishiki, the activity is due to the formation of the allyl alcohols.

Lipoxygenase Activity Increment in Infected Tomato Leaves and Oxidation Product of Linolenic Acid by Its In Vitro Enzyme Reaction

Our previous findings concerning the lipoxygenase (LOX) activity increment in infected rice plants and anti-fungus activity of resulting oxygenated fatty acids have prompted us to examine whether LOX activity increases in higher plants in response to infection with pathogens peculiar to individual plants. This study found that LOX activity increases in several kinds of infected higher plants, particularly in infected tomato leaves. Linolenic acid is oxidized to 9S-hydroperoxy-10E 12Z, 15Z-octadecatrienoic acid by the action of tomato LOX. This finding provides another example concerning the LOX activity increment in infected higher plant. The oxidation products had antimicrobial activity toward several kinds of pathogens.

Selective terminal olefin oxidation of n-3 polyunsaturated fatty acids

Abstract Through the action of N-bromosuccinimide in aqueous glyme, terminal double bond of n3 fatty acids was selectively converted to the corresponding bromohydrin. This evidence suggests the tight conformation of the n3 fatty acids in aqueous medium.

Synthesis of longithorone B, a sixteen-membered farnesylated p-benzoquinone

Abstract The intramolecular coupling reactions at the C-1 position of the 10Z-farnesyl moiety appended at the 2′-position of 4′-methoxy phenol derivatives were examined with the aid of Hf(OTf)4 and LiClO4. When the phenol was protected with a TBDMS group, meta coupling predominated while para coupling occurred efficiently when protected with a pivaloyl group. The para-coupled product was transformed to longithorone B, recently isolated from a tunicate.

An efficient construction of trinervitane and kempane skeletons from the common intermediate

Abstract Tricyclic trinervitane and tetracyclic kempane skeletons are constructed from the common intermediate possessing bicyclic secotrinervitane skeleton on the basis of biogenetical consideration.

Preparation of the enantiomers of hydroxy-C18 fatty acids and their anti-rice blast fungus activities

In order to examine the correlation between the anti-rice blast fungus activity and the chirality of allylic alcohols 1–3, which were characterized from the infected rice plants as an enantiomeric mixture with <10% e.e., a procedure for the chemical preparation of both enantiomers was explored, starting from the original fatty acids 4 and 5. The anti-rice blast fungus activities of both enantiomers of the allylic alcohols 1–3 and epoxy α-linolenic acids 12 and 13 demonstrate no noticeable correlation between the activity and chirality.

Synthesis of (1S,2R,12S)-2-hydroxy-11-dihydroneocembrene

Abstract Aiming at the asymmetric total synthesis of trinervitane-type diterpenes, an efficient synthetic route to the title compound was explored starting from the THP ether of pivaloyloxy geraniol 11e. The coupling reaction with Grignard reagent 14 bearing the stereogenic carbon proceeded smoothly to give the THP ether of (11S)-10-dihydrogeranylgeraniol 10. Conversion to the corresponding acid chloride through the intermediate 9, followed by cyclization, afforded the dihydrocembrene derivative 8, from which the title compound 7 was prepared.

Construction of Trinervitane and Kempane Skeletons Based on Biogenetical Routes

Based on the putative biogenesis of trinervitane- and kempane-type diterpenes (Scheme 1), a biogenetic-type transformation was simulated by cyclization of 7,16-secotrinervita-7,11,15-triene-2α,3α,17-triol (23) and of its 17-chloro derivative 30. The requisite substrates were prepared from geranylgeranoic acid chloride 6 (Schemes 2, 4, and 5). Treatment of 30 with AgClO4 at −20° provided the trinervitantrienediols 32 and 33 in 68 and 5% yields, while kempadienediol 35 was obtained in 50% yield by the same reagent at +20° (Scheme 7). The structures of the cyclization products were elaborated from detailed inspection of NMR spectra including H,H COSY, C,H COSY, and NOESY (Tables 1 and 2). The conformation of 30 and its plausible cyclization intermediate was discussed with the help of physical evidence, including X-ray crystallographic analysis.

Preparation of the enantiomers of 19-epoxy docosahexaenoic acids and their 4-hydroxy derivatives

Abstract By the action of NBS in aq. DME, dl -19-bromo-20-hydroxy-DHA methyl ester 5 was prepared, which was effectively resolved by lipase PS and vinyl acetate in the presence of a thiacrown ether to give 7 and 8 , each being transformed into the corresponding epoxides, 1 and 2 , respectively. The absolute configuration of 8 was established by the Kusumi–Moscher method. For the purpose of biological evaluation, both epoxides were converted to the γ-lactones 3 and their 4-hydroxy derivatives 4 .

A first synthesis of (±)-2,3-dihydroxytrinervitanes

The total synthesis of 2,3-dihydroxytrinervitanes, 1a and 1b, was performed from secotrinervitane-type allyl chloride 2