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At least 73 records · Page 4Linked to original sources
PubMed2004

Facile one-step synthesis of beta-alkoxy lactone via sequential lactonization and 1,4-addition of alkoxide group: total synthesis of all stereoisomers of dihydrokawain-5-ol.

We describe here a divergent total synthesis of all of the four stereoisomers of dihydrokawain-5-ol starting from alpha-D-glucose. The approach involves the use of Ando's modification of Horner-Wadsworth-Emmons homologation to give a alpha,beta-unsaturated ester. Subsequently, lactonization and 1,4-addition of OMe group in one step provided a delta-lactone, which was converted into the target compounds in two steps.

Journal Article↗
PubMed2001

Catalytic asymmetric access to alpha,beta unsaturated delta-lactones through a vinylogous aldol reaction: application to the total synthesis of the Prelog-Djerassi lactone.

[reaction--see text] A one-step catalytic asymmetric access to alpha,beta unsaturated delta-lactones is described, using a vinylogous Mukaiyama-aldol reaction between a gamma-substituted dienolate and various aldehydes in the presence of Carreira catalyst CuF.(S)-tolBinap. This methodology has been further applied to a straightforward access to the Prelog-Djerassi lactone.

Journal Article↗
PubMed2004

Gamma-lactone-tethered ring-closing metathesis. A route to enantiomerically enriched gamma-lactones alpha,beta-fused to medium-sized rings.

[reaction: see text] The stereoselective alkylation of alpha-(phenylsulfonyl)-beta-[(methoxycarbonyl)methyl]-gamma-lactones obtained by the base-induced cyclization of enantiomerically enriched alpha-[(phenylthio)acyl]-alpha,beta-unsaturated esters and ring-closing olefin metathesis (RCM) are the basis of a new approach for gaining access to gamma-lactones that are alpha,beta-fused to medium-sized carbocycles and cyclic ethers.

Journal Article↗
PubMed2004

Lactones. 21. Synthesis and odoriferous properties of lactones with the p-menthane system.

Starting from (R)-(+)- and (S)-(-)-pulegone, enantiomeric pairs of esters and lactones with the p-menthane system were obtained. The Claisen rearrangement of allylic alcohols and iodolactonization of gamma,delta-unsaturated acids were the key steps of syntheses presented. The structures of compounds were determined by both spectroscopic and crystallographic methods. Some of the synthesized compounds are characterized by interesting odoriferous properties.

Crystallography, X-Ray↗
PubMed2002

Asymmetric synthesis of polyhydroxy alpha-amino acids with the sulfinimine-mediated asymmetric strecker reaction: 2-amino 2-deoxy L-xylono-1,5-lactone (polyoxamic acid lactone).

Polyhydroxylated sulfinimines derived from protected 1,2-O-isopropyliden-L-threoses undergo the sulfinimine-mediated Strecker syntheses to give alpha-amino nitriles in good yield and de. A double stereodifferentiation effect was not observed and the diastereoselectivity is controlled by the absolute configuration of the sulfinyl group. Hydrolysis of the amino nitriles afforded the lactone rather than polyoxamic acid.

Amino Acids↗
PubMed2005

Enantioselective total syntheses of (-)-clasto-lactacystin beta-lactone and 7-epi-(-)-clasto-lactacystin beta-lactone.

An alkylidene carbene 1,5-CH insertion has been used as a key step in an efficient enantioselective total synthesis of (-)-clasto-lactacystin beta-lactone, and its C7-epimer. An additional noteworthy feature of the synthesis is the use of a novel oxidative deprotection procedure, utilizing DMDO, for the conversion of a late-stage benzylidene acetal into a primary alcohol and a secondary benzoate ester.

Alcohols↗
PubMed1990

Patch testing with the "sesquiterpene lactone mix": a marker for contact allergy to Compositae and other sesquiterpene-lactone-containing plants. A multicentre study of the EECDRG.

6278 patients were patch tested with a sesquiterpene lactone mix (SL-mix) in 10 European clinics. 4011 patients were tested only with 0.1% SL-mix, 63 (approximately 1.5%) of whom were positive, with 26 (41%) of these cases being considered clinically relevant. There were no cases of active sensitization, though 5 cases of irritation were reported. 22 irritant reactions and 22 cases of active sensitization occurred when testing also with 1% and 0.33% concentrations of SL-mix. SL-mix 0.1% pet. is shown to be an important patch test and many relevant sensitizations will be missed without routine screening with such a mix. Most patients with SL-mix sensitivity presented with hand and/or face dermatitis, apparent photodermatitis or more generalised eczema.

Dermatitis, Contact↗
PubMed2004

In vitro behaviour of sesquiterpene lactones and sesquiterpene lactone-containing plant preparations in human blood, plasma and human serum albumin solutions.

The interactions of the three sesquiterpene lactones (SLs) dihydrohelenalin acetate, dihydrohelenalin methacrylate and helenalin isobutyrate from Arnica montana and of parthenolide from Tanacetum parthenium as well as of three ethanolic Arnica preparations with human blood proteins using different matrices, human serum albumin (HSA), plasma and whole blood, were investigated. The extent of protein binding in human plasma or to human albumin differed significantly between individual SLs (dihydrohelenalin methacrylate < dihydrohelenalin acetate < helenalin isobutyrate << parthenolide), e. g., 30 % to 50 % of the SLs were bound to plasma. On the whole, SLs in the ethanolic preparations showed a lower degree of protein binding. Interestingly, although HSA has a reactive thiol group at its cysteine-34 position which is prone to react with the alpha,beta-unsaturated carbonyl of SLs, our studies showed that less than 6 % of SLs are bound to this position within 60 minutes. Thus, a reaction with other amino acids as well as non-covalent interactions with plasma proteins have to be considered. Considering the biological activity of SLs in whole blood, our studies demonstrate that knowledge of their plasma protein binding is important for interpreting the reported data of in vitro and ex vivo assays.

Arnica↗
PubMed1993

Compositae dermatitis in a Danish dermatology department in one year (I). Results of routine patch testing with the sesquiterpene lactone mix supplemented with aimed patch testing with extracts and sesquiterpene lactones of Compositae plants.

To investigate the frequency of Compositae sensitivity, the recently-developed sesquiterpene lactone mix (SL mix) was included in the standard patch test series. Patients with positive reactions to this or patients suspected of having a Compositae allergy were supplementarily tested with a Compositae mix, consisting of ether extracts of 5 European Compositae plants. In the first year, 686 patients were tested with the SL mix and 79 with the Compositae mix. A total of 31 Compositae-sensitive patients (4.5%) were found. The frequency of positive reactions to either of the mixes was equal, but only 17 of 30 patients tested were positive to both mixes. Testing with the individual ingredients of the Compositae mix showed frequent positive patch test reactions to feverfew, followed in order by chamomile, tansy, yarrow and arnica. The reason for this distribution is discussed and the results of standard, photo- and other plant patch tests are presented. The only partial overlap between positive reactions to the mixes emphasizes the necessity of supplementary testing in patients suspected of Compositae allergy, as well as the lack of a reliable single screening agent. Since no cases of active sensitization or irritant reactions were seen, both the SL mix and the Compositae mix may be considered suitable for routine screening of Compositae allergy.

Adult↗