Katsuyuki Nakashima

Chemical and genetic diversity of Ligularia vellerea in Yunnan, China

Intra-specific diversity in Liularia vellerea growing in the northwestern to central Yunnan province of China was studied by chemical and genetic approaches. Samples collected in the Jianchuan, Lijiang, and Zhongdian areas contained 6,15-dioxygenated furanoeremophilanes as their major components (type A); whereas samples from the Luguhu area accumulated 1,6-dioxygenated furanoeremophilanes (type B); a sample from near Kunming, however, contained 6,15-dioxygenated eremophilanolides (type C). 11 beta H- and 11 alpha H-6 beta-angeloyloxy-15-carboxyeremophil-7-en-12,8-olides (eremofarfugins D and E) were also isolated and their structures were determined. A correlation between the composition and the DNA sequence was observed in the ITSs.

Antioxidation mechanism studies of caffeic acid: Identification of antioxidation products of methyl caffeate from lipid oxidation

As a part of a research project on the elucidation of the chain-breaking antioxidation mechanism of natural phenols in food components, caffeic acid, a polyphenolic acid widely distributed in edible plants, was investigated. The identification and time course analysis of the antioxidation reaction products from methyl caffeate were carried out in the ethyl linoleate oxidation system. The antioxidation reaction produced a quinone derivative of methyl caffeate as an antioxidation product during the initial stage, which was identified by (13)C NMR. The quinone, however, was not the final product, and a further reaction occurred to produce several new peroxides. The isolation and structure determination of the peroxides revealed that they had tricyclic structures, which consisted of ethyl linoleate, methyl caffeate, and molecular oxygen. On the basis of the formation pathway of these products, an antioxidation reaction mechanism of methyl caffeate, including the redox reaction of the caffeate and Diels-Alder reaction of the produced peroxides, was proposed.

Eremofarfugin A and eremopetasitenin B3, two new eremophilanolides from Farfugium japonicum

Abstract Two new eremophilanolides, eremofarfugin A and eremopetasitenin B 3 , have been isolated from the methanol extract of fresh rhizomes of Farfugium japonicum (Compositae) and their structures have been determined on the basis of high resolution 2D NMR analysis.

Four alkaloids, lucidine B, oxolucidine A, lucidine A, and lucidulinone from Lycopodium lucidulum.

The structures of four alkaloids extracted from Lycopodium lucidulum (Lycopodiaceae) were established by X-ray and 2D NMR spectroscopic analyses. The dihydro-derivative of oxolucidine A, which was obtained by NaBH4 reduction of oxolucidine A, was treated with p-bromobenzoyl chloride to afford crystals, whose X-ray crystallographic analysis established the stereostructure, including the absolute configuration. The 2D NMR spectra of tetrahydrodeoxylucidine B were fully analyzed to establish the full structure of lucidine B, and the hitherto unknown stereochemistry at the C-14 position was established as beta-H. The structure of a new alkaloid, lucidulinone, was determined by spectroscopic analysis to be luciduline lactam.

Revised structure of caespitenone isolated from the liverwort Porella caespitans var. setigera and Porella swartziana

Abstract Caespitenone, previously isolated from the liverwort P. caespitans , has also been found in the close species P. swartziana collected in Colombia and its structure revised to have an africane-type based on the extensive 2D NMR analyses. The absolute configuration has been assigned by chemical transformations and allyl benzoate rule.

Total synthesis of coronafacic acid through 6-endo-trig mode intramolecular cyclization of an enone-aldehyde to a hydrindanone using samarium(II) iodide

Abstract Coronafacic acid has been synthesized from a hydrindanone prepared by a 6- endo - trig mode cyclization reaction of the enone-aldehyde with samarium(II) iodide. The stereochemistry of the hydrindanone was controlled by the coordinated samarium species resulting in cis in respect of the hydroxyl group at C-4 and the juncture proton at C-3a.

Structure of oxolucidine A, a lycopodium alkaloid

Abstract A Lycopodium alkaloid, oxolucidine A, was treated with NaBH 4 followed by p -bromobenzoyl chloride to afford a tribenzoate derivative, which was analyzed by X-ray crystallography to establish the stereostructure. The structure of lucidine A was also determined from these results except for the configuration at C-14.

Structure Determination of an Ag I -Mediated Cytosine–Cytosine Base Pair within DNA Duplex in Solution with 1 H/ 15 N/ 109 Ag NMR Spectroscopy

The structure of an Ag(I) -mediated cytosine-cytosine base pair, C-Ag(I) -C, was determined with NMR spectroscopy in solution. The observation of 1-bond (15) N-(109) Ag J-coupling ((1) J((15) N,(109) Ag): 83 and 84 Hz) recorded within the C-Ag(I) -C base pair evidenced the N3-Ag(I) -N3 linkage in C-Ag(I) -C. The triplet resonances of the N4 atoms in C-Ag(I) -C demonstrated that each exocyclic N4 atom exists as an amino group (-NH2 ), and any isomerization and/or N4-Ag(I) bonding can be excluded. The 3D structure of Ag(I) -DNA complex determined with NOEs was classified as a B-form conformation with a notable propeller twist of C-Ag(I) -C (-18.3±3.0°). The (109) Ag NMR chemical shift of C-Ag(I) -C was recorded for cytidine/Ag(I) complex (δ((109) Ag): 442 ppm) to completed full NMR characterization of the metal linkage. The structural interpretation of NMR data with quantum mechanical calculations corroborated the structure of the C-Ag(I) -C base pair.

Total Synthesis of (-)-(7S,10R)-Calamenene and (-)-(7S,10R)- 2-Hydroxycalamenene by Use of a Ring-Closing Metathesis Reaction. A Comparison of the cis- and trans-Isomers

The title compounds have been synthesized starting from l-menthone by application of a ring-closing metathesis reaction to confirm their reported absolute and relative stereochemistry. Comparisons of the NMR spectra and specific rotations are also discussed.

Total synthesis of optically active liverwort sesquiterpenes, trifarienols A and B, using phenylethylamine as a chiral auxiliary

Abstract The imine of ( rac )-2,3-dimethylcyclohexanone 10a with ( S )-(−)-phenylethylamine was reacted with methyl acrylate to yield methyl (1′ S ,6′ R )-3-(1′,6′-dimethyl-2′-oxocyclohexyl)propanoate 4a in 26% (97% ee) after hydrolysis. When (2 RS ,3 R )-2,3-dimethylcyclohexanone 10b was used, the same product 4b was obtained in 59% yield (>99.5% ee) after hydrolysis. When (2 RS ,3 R )-2,3-dimethylcyclohexanone 10b and ( R )-(+)-phenylethylamine were used, the reaction underwent in only 5% yield, the products being 4c , 12 , 13 , 14 , and 15 . Thus, the reaction of 3b with methyl acrylate is a matched case, while that of 3c is a mismatched case. These phenomena are explained by the nonbonded interaction of methyl acrylate with chiral phenylethylamine and the methyl group at the 6′-position of the cyclohexanone ring in the transition state. The propanoate product 4b was successfully transformed into liverwort sesquiterpene (+)-trifarienol A 1 and (−)-trifarienol B 2 in 10 steps. We have developed an HPLC method to determine the ees of 2,2-disubstituted and 2,2,3-trisubstituted cyclohexanones using the corresponding pentafluorophenyl esters.