Katsura Seki

Synthesis of chiral [5]helicenes using aromatic oxy-Cope rearrangement as a key step

Abstract Both enantiomers of ( P )-(+)-2- and ( M )-(−)-2-acetoxy-11,14-dimethyl[5]helicenes 8 were synthesized by asymmetric aromatic oxy-Cope rearrangement of the corresponding chiral bridged bicyclic compounds, which were obtained by enzymatic resolution. The absolute configurations of 8 were assigned by their circular dichroism spectra.

Phenols and a dioxotetrahydrodibenzofuran from seeds of Iris pallasii

Abstract Three new compounds, along with four known ones, have been isolated from the seeds of Iris pallasii . On the basis of spectroscopic methods and chemical evidence, the new compounds were shown to be 2-[(Z)-10-heptadecenyl]-4,6-dimethoxyphenol, 3,5-dimethoxy-[(Z)-10-heptadecenyl]benzene and 9,9b-di[(Z)-10-heptadecenyl]-4a,8-dihydroxy-2,7-dimethoxy-1,4-dioxo-1,4,4a,9b-tetrahydrodibenzofuran. The biogenetic relationships between these compounds are also discussed.

Iristectorene B, a monocyclic triterpene ester from Iris tectorum

Abstract A monocyclic triterpene ester, iristectorene B, has been isolated from the seeds of Iris tectorum . On the basis of spectroscopic methods and chemical evidence, the ester was shown to be 3-{3-hydroxy-2-[5-hydroxy-4,8,12- trimethyl-( 3E,7E )-3,7,11-tridecatrienyl]-2,3-dimethyl-6-(1-methyl-2-oxoethylidene)cyclohexyl} propyl tetradecanoate and its stereochemistry was also clarified.

Linderanolides and isolinderanolides, ten butanolides from Lindera glauca

Abstract Ten new (+)-hydroxybutanolides, linderanolides A-E and iso linderanolides A-E, along with one known one have been isolated from the leaves of Lindera glauca . On the basis of spectroscopic methods and chemical evidence, linderanolides A-E were shown to be (3 R ,2 Z )-3-hydroxy-4-methylenebutanolides having 2-((11 E )-11-tetradecenylidene), 2-tetradecylidene, 2-((7 Z ,10 Z )-7,10-hexadecadienylidene), 2-((7 Z )-7-hexadecenylidene) and 2-hexadecylidene side-chains, respectively, while iso linderanolides A-E were their corresponding (2 E )-isomers.

Iristectorones A-H, spirotriterpene-quinone adducts from Iris tectorum

Abstract Eight tetracyclic spirotriterpene derivatives, iristectorones A-H, have been found in the seeds of Iris tectorum . Their structures were established to be the Diels-Alder products of 2-methoxy-6-[( Z )-10-pentadecenyl]- p -benzoquinone with triterpenic conjugated trienes having spiro [4.5] decane skeleton derived from iristectorenes A-H, respectively, on the basis of spectral methods and chemical transformations. A possible biogenetic route for these esters has been also discussed.

Synthesis of 2-acetoxy[5]helicene by sequential double aromatic oxy-Cope rearrangement

Abstract Synthesis of 2-acetoxy[5]helicene has been achieved by sequential double aromatic oxy-Cope rearrangement strategy. Combination of 1-methoxybicyclo[2.2.2]oct-5-en-2-one and p -bromophenylmagnesium bromide gave 3-bromophenanthrene through several steps including an aromatic oxy-Cope rearrangement as a key step. The second oxy-Cope rearrangement and the following transformation gave 2-acetoxy[5]helicene by similar procedure.

Two methoxybutanolides from Lindera glauca

Abstract Two (-)-methoxybutanolides have been isolated from the rhizomes of Lindera glauca . On the basis of spectroscopic methods, their structures were elucidated to be (3 S ,2 E )-2-(11-dodecenylidene)-3-methoxy-4-methylenebutanolide and (3 S ,2 E )-2-(11 -dodecynylidene)-3-methoxy-4-methylenebutanolide, respectively.

Iristectorenes A and C-G, monocyclic triterpene esters from Iris tectorum

Abstract Six new triterpene esters, iristectorenes A and C-G, along with one known one have been found in the seeds of Iris tectorum . On the basis of spectroscopic methods and chemical evidence, the esters were established to be 3-{3-hydroxy-2-[5-hydroxy-4,8,12-trimethyl-(3 E ,7 E )-3,7,1 1-tridecatrienyl]-2,3-dimethyl-6-(1-methyl-2-oxoethylidene)-cyclohexyl}propyl ( Z )-9-tetradecenoate,( Z )-11-hexadecenoate, ( Z,Z )-9,12-octadecadienoate, hexadecanoate, ( Z )-11-octadecenoate and octadecanoate, respectively.

Belamcandones A-D, dioxotetrahydrodibenzofurans from Belamcanda chinensis

Abstract Four new enediones, belamcandones A-D, have been isolated from the seeds of Belamcanda chinensis . On the basis of spectroscopic methods and chemical evidence, they are concluded to be 4a,8-dihydroxy-2,7-dimethoxy-1,4-dioxo-1,4,4a,9b- tetrahydrodibenzofurans having two alkyl side-chains at the C-9 and C-9b positions.

Insoluble monolayers of irisquinone and its related substances at the air/water interface

Abstract Monolayers of irisquinone, trans-irisquinone, dihydroirisquinone, 3-hydroxyirisquinone, 3-hydroxydihydroirisquinone, and their corresponding unsaturated long-chain alcohols were studied using pressure-area (π-A) isotherms. All the materials studied form stable monolayers at the air/water interface and the characteristic molecular arrangements of the quinone derivatives in monolayers were presumed from the π-A isotherms. The contribution of the hydrophilic quinone headgroups and the hydrophobic alkyl chains to the characteristic molecular arrangements was discussed. Three of the five types of the materials exhibit the liquid-expanded/liquid-condensed transitions with compression at certain temperature regions. A thermodynamic treatment was applied to the transitions.