Takashi Ooi

Structure Revision of Circumdatins A and B, Benzodiazepine Alkaloids Produced by Marine Fungus Aspergillus ostianus, by X-ray Crystallography

The structures of circumdatins A and B, pentacyclic alkaloids produced by Aspergillus ostianus, were revised from the previously reported betaine structures to unique oxepin ones by X-ray crystallography. The co-occurring known alkaloids, circumdatins D, E, and H, and a new compound reported here, circumdatin J, have a common framework.

Three New Polyketide−Terpenoid Hybrids from Penicillium sp.

Three novel hybrid polyketide-terpenoid metabolites were isolated from a Penicillium minioluteum strain. Their structures were determined by NMR spectroscopic analyses and X-ray crystallography. The proposed biosynthetic pathway including a unique retro-Claisen migration of methyl carbonate correlates the three compounds with berkeleydione and berkeleytrione.

Isolation and Absolute Configuration Determination of Aliphatic Sulfates as the Daphnia Kairomones Inducing Morphological Defense of a Phytoplankton—Part 2

4,8-Dimethylnonyl sulfate (1) and 3-methyl-4E-decenyl sulfate (2) were isolated from Daphnia pulex as the Daphnia kairomones that induced morphological defense of a freshwater phytoplankton Scenedesmus gutwinskii var. heterospina (NIES-802). The absolute configuration at C4 of 1 was determined by Ohruis method applied to alcohol 3. The absolute stereochemistry at C3 of 2 was determined by (1)H-NMR analysis of the (R)-1NMA ester of alcohol 11.

Determination of the absolute configuration of linear secondary alcohols adopting one enantiomer of the chiral anisotropic reagents, methoxy-(1-and 2-naphthyl)acetic acids

Abstract The absolute configurations of the aliphatic secondary alcohols can be determined by NMR spectroscopy using only one enantiomer of the chiral anisotropic reagents, 1NMA and 2NMA.

Application of the modified Mosher's method to linear 1,3-diols

Abstract Absolute configurations of linear 1,3-diols can be determined by NMR spectroscopy by means of the modified Moshers method.

Absolute Configurations of Some Hydroxy-fatty Acids Produced by the Insect Genus Laccifer

The absolute configurations of some hydroxy-fatty acids were examined by the modified Moshers method proposed by Ohtani et al. The absolute configurations of the major components were determined from NMR data of their ΜΤΡΑ esters and 2-ΝΜΑ esters. The application of Moshers method for the anti-glycol is discussed.

Leishmanicidal activities and cytotoxicities of bisnaphthoquinone analogues and naphthol derivatives from Burman Diospyros burmanica

A methanol extract of the wood of Diospyros burmanica, collected in Burma (Myanmar), was found to exhibit significant activity against Leishmania major. Subsequent chromatographically resolved fractionation led to the isolation of three novel bisnaphthoquinone analogues, burmanin A, B, and C (1-3), together with nine known compounds (4-12). The structure of 1 was confirmed by X-ray crystallography, and those of 2 and 3 by spectroscopic techniques, including 1D and 2D NMR. The inhibitory activities of the isolates were evaluated against the promastigote forms of Leishmania major and the murine macrophage-like cell line, RAW264.7.

Absolute stereostructure of a 2,3,7,13-tetrahydroxyoctadecanoic acid, the framework of taurolipid B produced by a fresh-water protozoan, Tetrahymena thermophila

Abstract The absolute configuration of the four asymmetric centers of 2-(2,3,7,13-tetrahydroxyoctadecanoylamino)ethanesulfonic acid, which is the framework of taurolipid B isolated from a fresh-water protozoan, Tetrahymena thermophila , as one of the major taurolipids, has been determined by NMR-spectroscopy with the use of a new chiral anisotropic reagent, 2ATMA, as well as CD spectroscopy.

X-ray structures of two stephacidins, heptacyclic alkaloids from the marine-derived fungus Aspergillus ostianus

Two stephacidins, 21-hydroxystepahcidin and notoamide F, were isolated from the cultivation medium of the marine-derived fungus Aspergillus ostianus, and their structures were confirmed by X-ray crystallography.

A simple preparation of 17(R)-hydroxyeicosatetraenoic and eicosapentaenoic acids from the eicosanoylphloroglucinols, components of the brown alga, Zonaria diesingiana

Abstract The alkaline treatment of 17(R)-hydroxyeicosatetraenoylphloroglucinol and eicosapentaenoylphloroglucinol, which are the major components of the methanol extract of the brown alga, Zonaria diesingiana (Dictyota) afforded 17(R)-hydroxyeicosatetraenoic and eicosapentaenoic acids, respectively, in good yields. The conformation of methyl ester of the 17(R)-hydroxy acid in a solution was studied by using 2NMA, a chiral anisotropic reagent.