Search

Natural (3E,6R,7R)- and (3Z,6S,7S)-laurediols were subjected to enzymatic reaction with the partially purified bromoperoxidase from the red alga, Laurencia nipponica, in the presence of H2O2 and NaBr to afford laurencin and prelaureatin, respectively. The further reaction of these products with bromoperoxidase gave rise to the bicyclic bromo-ethers.

The compound with all the necessary functional groups of the KLM ring system in ciguatoxin, which is one of the most complicated toxic substances of marine origin, was synthesized stereoselectively. The crucial steps involve construction of the ethynyl alcohol, the δ-valerolactone, and the natural acetals.

The A- and B-ring system of hemibrevetoxin-B, which has been isolated from the red tide organism, Gymnodinium breve, has been synthesized in an optically pure form starting from δ-valerolactone.

Reaction of 2,3-epoxy-1-ol methanesulfonates with diethylaluminum chloride or with the mixture of diethylaluminum chloride and diethylamine hydrobromide in dichloromethane gave rise to regioselectively the corresponding 3-chloro- and 3-bromo-1,2-diol 1-methanesulfonates, respectively, in excellent yields.

The first biosynthetic in vitro evidence for marine natural bromo-ethers by using lactoperoxidase is reported.

2-Heptenolide was smoothly transformed into the α,β,γ,δ-dienol triflate, which was reacted with lithium dialkylcuprates to afford α-alkylated oxocenes in good yields. The methodology was applied effectively to the synthesis of (+)-lauthisan.

Molecular sieves improved the reproducibility of the cyclization catalyzed by La(Otf)3 in the 5-hydroxy-2-methoxymethyl-1,2-epoxide system, and addition of methanol raised the desired endo-selectivity.

The total syntheses of (12R,13R)-(−)-obtusenynes and (12S,13R)-(+)-obtusenynes were achieved. The absolute configurations of the obtusenynes isolated by Norte from Laurencia pinnatifida were clarified as the former.

In the reductive lithiation of 2-phenylthiooxolane system, the coexistence of the substituents at C2 and C3 with cis-configuration was found to increase the ratio of 2,5-trans-2-lithiooxolane at 2,5-cis derivative.

trans-1-Bromo-8-t-butyldiphenylsiloxy-4,5-epoxyoctane was treated with AgOTf in THF/H2O (5:1) to give trans-3-hydroxytetrahydropyran derivative as the major product (72%) by the expansion of the oxirane ring.

A metabolite has been isolated from winter wheat leaves inoculated with H2O2 and its structure was elucidated from the spectral data.

Sweet potato, kidney bean, and sugar beet, when infected with Fusarium roseum, Fusarium solani, and Rhizoctonia solani, respectively, generated H2O2 which then elicited accumulation of the phytoalexins in the respective cases. The three intact plant tissues, only when treated with H2O2, induced phytoalexin production, respectively.

On treatment with hydrogen peroxide, potato tubers released an endogenous elicitor for phytoalexin production. The homogenous active substance, purified by gel filtration and anion exchange column chromatographies, is an acidic polysaccharide with MW 9,200. This constitutes the first isolation of a self-induced endogenous elicitor.

Potato tuber tissues, when infected with Phytophthora infestans or treated with arachidonic acid, generated H2O2 which then elicited accumulation of the phytoalexins. The plant tissues, when treate...

Construction of the sugar part of polycavernoside-A, which has been isolated as one of toxic principles from the red alga Polycavernosa tsudai, is described starting from L-fucose and D-xylose in order to elucidate the relative stereochemistry.

In a course of studies on glycinoeclepin A, which is a natural hatching stimulus for the soybean cyst nematode isolated from the roots of kidney bean, the relationship of the structure and activity...

Titanium-mediated ring openings of 3,4-epoxy-1-ols at the 4-position with diethylamine hydrohalides proceeded efficiently in dichloromethane, while the requisite openings of 2,3-epoxy-1-ols at the 3-position in benzene.

Deacetyllaurencin was synthesized in an enzymatic manner from (3E,6R,7R)-laurediol with lactoperoxidase in the presence of hydrogen peroxide and sodium bromide.

Treatment of 11α-hydroxy-, 11α-acetoxy-, and 11-oxo-17α-acetyl-12α,13α-epoxyetiojervanes (1, 1a, and 11) with boron trifluoride etherate gave mixtures of several compounds, respectively, including interesting rearranged products, e.g., compounds (12 and 13) with bicyclo[3.3.1]nonane-2,9-dione and hydrooxepin moieties.

Structure and configuration of rishitinone, a stress metabolite isolated from diseased potato tubers, was determined to be formula 1 on the basis of the chemical and spectral evidence.

(4RS,7RS)-11-Hydroxy-15-norsolavetivane, a versatile intermediate for the synthesis of all 15-oxygenated T-type spirovetivanes, has been synthesized with high stereoselectivity. The synthesis has also been applied to preparation of (±)-[8,8-2H2]isolubimin.

The synthesis of (±)-glutinosone, an antifungal norsesquiterpene from Nicotiana glutinosa infected with tobacco mosaic virus, is described.

The title compound, one of the most important starting materials for the synthesis of C-nor-D-homosteroid and normal steroid hormones, was determined to possess (E)-configuration at the 17,20-double bond on the basis of the chemical and spectral evidence.

Lactone enolates were treated with N-phenyl triflimide in the presence of hexamethylphosphoric triamide to afford smoothly the corresponding enol triflates, which, on reaction with lithium dialkylcuprates, gave rise to alkylated cyclic ethers in good yields.

Cationic cyclization of bromohydrins of geranonitrile and homogeranonitrile in the presence of boron trifluoride complexes proceeded smoothly, giving mixtures of bromo cyclic olefins in satisfactory yields. This cyclization method was applied to the synthesis of (±)-snyderols.

Isolation of rishitin-M-1, a metabolite of rishitin produced in healthy tissues of white potato, from diseased potato tuber slices and its convenient preparation from rishitin are described.

The configuration of (+)-glutinosone was determined on the basis of the chemical transformation from (−)-rishitin and the NMR spectrum in the presence of the shift reagent.

Titanium-mediated ring openings of 2,3-epoxy-l-ols at the 3-position have been performed more efficiently with use of dialkylamine hydrohalides as sources of halide nucleophiles.

For studies on the vital metabolic pattern of rishitin, a representative phytoalexin of diseased potatoes, (−)-[12,12-2H2]rishitin has been synthesized stereoselectively from (11S)-2α-acetoxy-3-oxo-4β,5α-eudesman-6β,12-olide.

The title compound, isolated newly as a metabolite from solavetivone, was converted into lubimin in potato.