Search

A new benzyl benzoate glycoside and five new 3-deoxy-d-manno-2-octulosonic acid derivatives were isolated from the entire plant of Solidago decurrenstogether with three known compounds. Their structures were established by extensive analyses of their 1D and 2D NMR spectra and by comparison with physical data of known compounds.

The bark extract of Acacia mearnsiishowed strong lipase and α-amylase inhibition activities. Fractionation of the extract by column chromatography and subsequent 13C NMR and MALDI-TOF-MS analysis revealed that the active substances are proanthocyanidin oligomers mainly composed of 5-deoxyflavan-3-ol units. In addition, 4′-O-methylrobinetinidol 3′-O-β-d-glucopyranoside, fisetinidol-(4α,6)-gallocatechin, and epirobinetinidol-(4β,8)-catechin were isolated as new compounds, and their structures were determined from spectroscopic data. Furthermore, a modified thiol degradation method using strongly acidic conditions was applied to the extract to yield three thiol degradation products derived from robinetinidol units. This method is useful for characterizing acacia proanthocyanidins (wattle tannins).

Degradation of the black tea pigment theaflavin was examined in detail. Enzymatic oxidation of a mixture of epigallocatechin and epicatechin initially produced theaflavin, while prolonged reaction decreased the product. Addition of ethanol to the reaction mixture at the point when theaflavin began to decrease afforded four new products, together with theanaphthoquinone, a known oxidation product of theaflavin. The structures of the new products were determined by spectroscopic methods. One of the products was an ethanol adduct of a theanaphthoquinone precursor, and this reacted with theaflavin to give two further products. A product generated by coupling of theaflavin with epicatechin quinone was also obtained. The structures of the products indicate that oxidation and coupling with quinones are key reactions in the degradation of theaflavins. The degradation of theaflavin probably contributes to production of thearubigins.

Two new bicyclic polyketide lactones, polyrhacitides A ( 1) and B ( 2), were isolated from Chinese medicinal ants, Polyrhacis lamellidens, which have been used as an effective therapeutic agent to treat rheumatoid arthritis and hepatitis in China. Their absolute structures were elucidated on the basis of spectroscopic analyses and chemical evidence. The occurrence of polyketides with similar structures in plants of the Lamiaceae, Lauraceae, and Staphyleaceae indicates their significance in the study of chemical ecology.

Four hydrolyzable tannins named balanophotannins D−G ( 1– 4) were isolated from the aerial parts of the parasitic plant Balanophora japonica. Their structures were characterized on the basis of spectroscopic and chemical evidence. Balanophotannins D−G contain an oxidized hexahydroxydiphenoyl (HHDP) group. The absolute configurations of balanophotannins D ( 1) and F ( 3) were determined via the PGME method. Balanophotannin E ( 2) showed cytotoxicity to Hep G2 cancer cells with an IC 50value of 4.22 µM.

Troponoids were shown to form 2:1-complexes with β-cyclodextrin and 1:1-complexes with α-cyclodextrin. The photoisomerization of complexed tropolone and 2-methoxytropone gave optically active 1-hydroxy- and 1-methoxybicyclo[3.2.0]hepta-3,6-dien-2-ones in improved yields. The pyrolysis of the (+)-1-methoxybicyclo[3.2.0]hepta-3,6-dien-2-one gave the (+)-3-methoxybicyclo[3.2.0]hepta-3,6-dien-2-one, ruling out the two-fold supra-antara-1,3-sigmatropy.

Starting from 4,4-dimethylcyclopentene, the protoilludane skeleton was prepared by two steps of photocycloadditions and methylation with a Grignard reagent. A series of transformations on these products led to protoillud-7-ene and some derivatives.

Unlike ethylene, 1,1-dimethoxyethene, an electron-rich olefin, has been photocycloadded to a cis-hexahydroindenone to form a norprotoilludane derivative with a correct stereostructure. Methylation and subsequent chemical transformations yielded several oxygenated derivatives, from which the parent hydrocarbon, protoillud-7-ene, was obtained by deoxygenation. Independent evidence for the stereostructures of the synthetic derivatives has been provided by the X-ray crystallographic analysis of a dihydroxy acetal.

Optically active (-)- and (+)-2,2',6,6'-tetrafluorobiphenyl-3,3'-dicarboxylic acids were obtained through brucine salts. The half-life times for racemization of their dimethyl esters were estimated at various temperatures and the activation energy was calculated to be 25.6 kcal/mol.

Treatment of a mixture of epicatechin and epigallocatechin with extracts of fresh tea leaf or banana fruit generated a new pigment named theanaphthoquinone, which has a 1,2-naphthoquinone moiety oxidatively derived from the benzotropolone unit of theaflavin.

Two new rottlerin-like phloroglucinol derivatives were detected from the fruits of Mallotus japonicusand identified as 3-(3,3-dimethylallyl)-5-(3-acetyl-2,4-dihydroxy-5-methyl-6-methoxybenzyl)-phlorobutyrophenone and -phloroisobutyrophenone by spectral studies. 2,6-Dihydroxy-3-methyl-4-methoxyacetophenone was also isolated

From the root of Lindera strychnifolia , which is well known to contain many kinds of sesquiterpenes, a new bisesquiterpene has been isolated. The structure of this compound was elucidated by spectroscopic analysis, including COSY, HMBC and HMQC techniques.

The structure of a base catalyzed rearrangement product of pseudoanisatin has been determined by an X-ray crystallographic analysis as the formula, indicating a novel stereoselective reaction which includes steric inversion at C-3 and C-4. The reaction mechanism is discussed.

Pyrolysis of 2-[(E)-4-bromo-3-butenyloxy]tropone and 2-[(E)-4-bromo-2-methyl-2-butenyloxy]tropone produced 3-methyl-3-vinyl-2,3-dihydro-8H-cyclohepta[b]furan-8-one and 3-isopropylidene-2,3-dihydro-8H-cyclohepta [b]furan-8-one, which established the involvement of 3,3-sigmatropy for furotropone formation.

The chemotaxonomical study of Castanopsis species leads to the isolation of two previously unknown flavanols.

Review: 112 refs.

isolation, structure elucidation and biological activity of the new diketopiperazine derivatives bacillusamides A (Ia) and B (b)

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.