Search results for "ASTER"
showing 10 items of 2223 documents
Omphalocarpoidone, a new lanostane-type furano-spiro-γ-lactone from the wood of Tridesmostemon omphalocarpoides Engl. (Sapotaceae)
2013
Abstract Phytochemical studies of the wood and the stem bark of Tridesmostemon omphalocarpoides Engl. (Sapotaceae) led to the isolation of omphalocarpoidone (1), a new lanostane-type furano-spiro-γ-lactone together with β-amyrin acetate (2), taraxerol (3), spinasterol (4), lichexanthone (5), epi-catechin (6), spinasterol 3-O-β- d -glucopyranoside (7), tormentic acid (8), and 1,2,3,4-tetrahydronorharman-1-one (9). Their structures were established on the basis of extensive NMR studies, mass spectrometry, and by comparison of the data with those previously reported in the literature. The structure of the new secondary metabolite was later confirmed by X-ray crystallography. Except for spinast…
Synthesis of nonracemic α-trifluoromethyl α-amino acids from sulfinimines of trifluoropyruvate
2001
We describe a novel and useful method for the synthesis of nonracemic α-trifluoromethyl α-amino acids (α-Tfm-AAs). Key building blocks are the sulfinimines (S)-1a and (S)-1b, prepared by Staudinger reaction from trifluoropyruvate esters and the chiral N-sulfinyl iminophosphorane (S)-8, which were treated with benzyl, allyl, and alkylmagnesium halides. The resulting diastereomeric N-sulfinyl α-Tfm α-amino esters, 12 and 13, were produced with moderate to good stereoselectivity and yields. When alkyl Grignard reagents were used, stereocontrol became progressively higher with increasing steric bulk, while reversed, though poor, stereocontrol was achieved with benzyl/allyl Grignard reagents. An…
Chemical characterization of traditional varietal olive oils in East of Spain
2013
Abstract The aim of this work has been to characterize the chemical composition of the eight most emblematic varietal olive oils from the West of the Mediterranean Sea. These were classified into two groups according to the International Olive Council (IOC norms): Sweet oils (Farga, Morruda and Serrana) which were compared with Arbequina as standard of the Spanish sweet oils; and bitter–spicy oils (Alfafara, Blanqueta, and Villalonga) that were compared with Picual, considered as the standard of the bitter–spicy olive oils. For the study, sampled trees were chosen in their geographically separated originating areas. They were cultivated in the traditional conditions. The variety of each sam…
Flavones, sesquiterpene lactones and glycosides isolated from Centaurea aspera var. Stenophylla
1984
Abstract From the alcoholic extract of Centaurea aspera var. stenophylla benzoic acid, p-hydroxybenzoic acid, apigenin, 6-methoxyluteolin, 11,13-dehydromelitensin, melitensin, stenophyliolide, ethyl-7-O-apigenin-glucuronate and the glucosides of sitosterol and stigmasterol were isolated and characterized. Stenophyllolide was shown to be 9,15-dihydroxygermacra-1(10),4,11-trien-12,6-olide.
A new dibenzofuran and other constituents from Ligularia caloxantha, a Chinese medicinal plant.
2008
A new dibenzofuran named 1,2,4-trimethyl-7,8-dimethoxy-dibenzofuran (1), together with seven known compounds, euparin (2), 2,5-diacetyl-6-hydroxy-benzofuran (3), 2-acetyl-5,6-dimethoxy-benzofuran (4), gummosogenin (5), lupeol (6), stigmasterol (7) and (E)-2,5-dihydroxy-cinnamic acid (8), were isolated from the roots of Ligularia caloxantha, a Chinese medicinal plant. The structures of the compounds were elucidated by spectroscopic methods.
Isomotiol, a new triterpene from strychnos potatorum
1978
Isomotiol (fern-8-en-3β-ol) was isolated from the leaves of Strychnos potatorum; it was not known previously as a natural product, but it has been obtained by acidic isomerization of compounds with a fern-7-ene or a fern-9(11)-ene skeleton. From the leaves and the bark mixtures of sitosterol, stigmasterol and campesterol were also isolated.
Stereoselective synthesis of C-glycosyl compounds via Michael addition of trimethylsilyl enol ethers and enamines to hex-1-enopyran-3-uloses
1987
Abstract The titanium(IV)-catalyzed addition of trimethylsilyl enol ethers to 2,4,6-tri- O -acylhex - 1 - enopyran - 3 - uloses ( 3 and 4 ) gave stereoselectively 3,6 - di - O - acyl - 4 - deoxy - β - d - glycero -hex-3-enopyranosyl-2-ulose derivatives. The formation of the C -glycosyl bond was accompanied by a 2→3 acyl shift, followed by the elimination of the 4-acyloxy substituent. Similarly, the reaction of 1-pyrrolidinocyclohexene with 3 and 4 also led stereoselectively to 2-(2,4,6-tri- O -acyl-β- d - ribo -hexopyranosyl)cyclohexanones. In this Michael addition, among the eight possible diastereomers, only one was formed. The high stereocontrol of both C -glycosyl compound syntheses is …
Sesquiterpene lactones from Anthemis plutonia.
1998
Abstract Aerial parts of Anthemis plutonia furnished three guaianolides, one of them new.
A chemotaxonomic survey of Sonchus subgenus Sonchus
1993
Abstract Five species of Sonchus subgenus Sonchus were surveyed for their phenolic constituents. Seven flavonoids were identified: luteolin, luteolin-7-glucoside, apigenin, apigenin-3-glucoside, quercetin, quercetin-3-glucoside and quercetin-3-galactoside; three were phenolic acids; caffeic, chlorogenic and isochlorogenic; and two were coumarins: aesculetin and cichoriin. Their systematic significance for this genus is discussed.
Phytochemical constituents and chemosystematic significance of Pulicaria jaubertii E.Gamal-Eldin (Asteraceae)
2018
Abstract The chemical characterization of methylene chloride/methanol (1:1) extract of the air-dried whole medicinal plant, Pulicaria jaubertii E. Gamal-Eldin, led to isolation and identification of two new hydroquinone compounds; 2-(2-acetoxy propyl), 5-methyl hydroquinone (1) and 2-(2-hydroxy propyl), 5-methyl hydroquinone-4-O-β-D-glucopyranoside (2), four known flavonols (3-6) and 7 known dihydroflavonols (7-13). The structures were established depending upon comprehensive analysis of the NMR, IR and HR/EI-MS data. Herein, compounds 6, and 10-13 were isolated for the first time from this plant. The chemotaxonomic significance of the isolated flavonoids from P. jaubertii comparing with th…