1,721,023 research outputs found
Les connecteurs en discours. Le cas de "donc"
No full textLe traitement des connecteurs dans le cadre du courant linguistique d'"analyse du discours"; définition de "donc" dans le Trésor de la Langue Française informatisé
Application of molecular modelling to natural products: a biogenetic study of (+)-spathulenol and (+)-allospathulenol
No full textA conformational analysis of (+)-spathulenol and its related stereoisomers was performed using the semiempirical program MNDO. The obtained theoretical results were tested by checking the agreement of a selected calculated property (3J(H-H)) With the experimental value. The theoretical values of the vicinal coupling constants were calculated for all possible stereoisomers of spathulenol, including the ones not yet isolated, to allow their identification as natural and/or synthetic products. A biogenetic study was then undertaken using both the ''saddle'' technique, as implemented in the AMPAC package, and the coordinate reaction method. According to the results obtained, both spathulenol and allospathulenol should originate from two different conformations of a germacradiene precursor with both double bonds in the E configuration
SAPONINS FROM ALBIZZIA-LUCIDA
No full textThree main saponins were isolated from the seeds of Albizzia lucida. Their structures were established by spectral analyses and chemical and enzymatic transformations as 3-O-[beta-D-xylopyranosyl(1 --> 2)-alpha-L-arabinopyranosyl (1 --> 6)][beta-D-glucopyranosyl (1 --> 2)]beta-D-glucopyranosyl echinocystic acid; 3-O-[alpha-L-arabinopyranosyl (1 --> 6)][beta-D-glucopyranosyl (1 --> 2)]-beta-D-glucopyranosyl echinocystic acid and 3-O-[beta-D-xylopyranosyl (1 --> 2)-beta-D-fucopyranosyl (1 --> 6)-2-acetamido-2-deoxy-beta-D-glucopyranosyl echinocystic acid, characterized as its methyl ester
Isolation, synthesis, and antiplatelet aggregation activity of resveratrol 3-O-beta-D-glucopyranoside and related compounds
No full textResveratrol 3-O-beta-D-glucopyranoside (1) has been isolated from the seeds of Erythrophleum lasianthum (Caesalpinioidae, Leguminosae), a South African plant used in traditional medicine, and has shown antiplatelet aggregation activity. The synthesis of 1, related hydroxystilbenes, and their glucosides has been undertaken to provide larger quantities, for further biological evaluation, and has been accomplished via Wittig reactions followed by glucosylation under phase transfer catalysis
CONSTITUENTS OF THE FRUIT OF SOUTH-AFRICAN COMBRETUM SPECIES .1
No full textThe fruit of Combretum species are poisonous to human beings. In an attempt to isolate the toxin(s), a total of 16 compounds from four species have thus far been isolated and identified
9,10-SYN-PODOCARPANE DITERPENOIDS .6. DIELS-ALDER CYCLO-ADDITION OF (ACETOXYVINYL)CYCLOHEXENES TO QUINONES
No full text- …
