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Medium sized carbocycles are particularly difficult to synthesize. Ring closing metathesis reactions (RCM) have recently been applied to construct eight-membered carbocycles, but trisubstituted double bonds in the eight-membered rings are more difficult to produce using RCM reactions. In this review, model examples and our own results are cited and the… (More)
Two samples of Cremanthodium stenactinium (Asteraceae) were collected in Sichuan Province, China. From the ethyl acetate extracts of the roots, three new eremophilane-type sesquiterpenoids and one new trinoreremophilane compound were isolated, together with other known eremophilanes. Their structures were determined based on the spectroscopic data. This is… (More)
The prenyl ester and the phenylethyl ester of caffeic acid, formed in the bud excretion of poplar species, were shown recently to be the major contact allergens in bee-glue. An unambiguous synthesis of these compounds, based on the reaction of caffeic acid with 1-bromo-3-methyl-2-butene and with beta-bromoethylbenzene, respectively, is reported. The… (More)
The chemical and genetic diversity of Ligularia species in the Hengduan Mountains area of China is reviewed. A hypothesis that the production of furanoeremophilanes is ecologically advantageous is proposed.
Two samples of Ligularia kanaitzensis collected in the Shizhongshan Mountain region of Yunnan Province, as well as one sample collected in Sichuan Province, were analyzed with regard to root constituents and neutral DNA sequences. The two Shizhongshan samples were found to be different from each other and from other samples analyzed previously, indicating… (More)
Four new eremophilane-type sesquiterpenoid alcohols were isolated from Cremanthodium helianthus collected in China and their structures established on the basis of spectroscopic analyses. All of them had 9-en-8-one partial structures with one more double bond either delta11, delta11(13), or delta7(11). Two of them had a hydroxy group at C-1 position.
Esters of trans-4-hydroxycinnamic acid, cis-4-hydroxycinnamic acid and trans-3,4-dihydroxycinnamic acid with long-chain alcohols (n=15-20), were isolated from the stems of Calystegia soldanella.
The ethyl acetate-soluble fraction from a methanol extract of Ferula foetida has afforded six new sulfide derivatives, (E)-3-methylsulfinyl-2-propenyl sec-butyl disulfide (foetisulfide A) (1), (Z)-3-methylsulfinyloxy-2-propenyl sec-butyl disulfide (foetisulfide B) (2), (E)-3-methylsulfinyloxy-2-propenyl sec-butyl disulfide (foetisulfide C) (3),… (More)
Sixteen new thymol derivatives have been isolated from Eupatorium fortunei and their structures determined based on spectroscopic data. They were classified into three groups (i-iii) depending on the oxidation levels: (i) one oxygen function at the 9-position, (ii) two oxygen functions at the 8- and 9-positions, and (iii) three oxygen functions at the 8-,… (More)
Allylic alcohols were isomerized into ketones by the action of the Grubbs reagent. Some model alcohols were prepared and tested under similar conditions to reveal that less substituted alkenes rearrange more easily. More hindered alcohols are stable under these conditions, however, the simple allylic alcohols tend to isomerize producing ethyl ketone and the… (More)