Search results for "synthesis"
showing 10 items of 2844 documents
Reaction of lithium enediolates with perfluoroketene dithioacetals. Synthesis of α-trifluoromethyl γ-dicarboxylic acid derivatives
2004
The reaction of perfluoroketene dithioacetals with dianions of carboxylic acids proceeds through the substitution of the vinylic fluoride. The preparative value of this reaction depends strongly on the reaction and work-up conditions, the optimisation of which led to use LDA as a base and multiple extraction techniques. The overall process may be considered as a formal synthesis of α-trifluoromethyl γ-dicarboxylic acid derivatives.
Fluorous (Trimethylsilyl)ethanol: A New Reagent for Carboxylic Acid Tagging and Protection in Peptide Synthesis
2006
Starting with a fluorous analogue of 2-(trimethylsilyl)ethanol, we have designed an easy method for preparing a new fluorous tag ((F)TMSE) for the protection of carboxylic acids. Because mild conditions are employed in the tag cleavage (TBAF in the presence of 4 A molecular sieves, which prevent racemization), this tag can be advantageously used in the synthesis of peptides and modified peptides, as we have demonstrated with several examples, including the fluorous synthesis of short alpha- and beta-peptides as well as of modified fluorinated retropeptides.
Selective Formal Transesterification of Fluorinated 2-(Trimethylsilyl)ethyl α-Imino Esters Mediated by TBAF
2008
The scope of the transesterification reaction between beta-fluorinated alpha-imino esters and various electrophiles in the presence of TBAF as fluorine source is described. The reaction is highly selective for alkyl iodides, bromides, and mesylates, while alkyl chlorides react at a significantly slower rate and tosylates do not react under the reaction conditions. This methodology represents a simple and useful alternative for the preparation of a wide variety of fluorinated alpha-imino esters.
The Influence of (2-Chloroethyl)trimethylammoniumchloride (CCC) on Growth and Photosynthetic Metabolism of Young Wheat Plants (Triticum aestivum L.)
1984
Summary The influence of (2-chloroethyl)trimethylammoniumchloride on growth and cell metabolism of Triticum aestivum var. Kolibri was investigated. CCC was added to the nutrient solution on the 11th day of development with a final concentration of 10 −2 mol·1 −1 . It immediately stopped root growth and showed a strong inhibitory influence on the growth of the leaves. Smaller and fewer cells accounted for the reduction in final leaf size of about 40 %. The content of soluble proteins and soluble reducing sugars were significantly increased in the treated leaves. CCC also exhibited a stimulating effect on the synthesis of RubPc-ase protein and the in vitro activity of this enzyme. In contrast…
Inhibition of herpesvirus DNA synthesis by 9-beta-D-arabinofuranosyladenine in cellular and cell-free systems.
1977
9-beta-D-Arabinofuranosyladenine 5'-triphosphate (ara-ATP) is an inhibitor both of DNA polymerase-alpha and -beta from noninfected rabbit kidney cells and of the DNA-dependent DNA polymerase induced by herpes simplex virus Type 1 (strain IES). The studies were performed with partially purified enzymes, and each of the different polymerase preparations contained only one DNA-dependent DNA polymerase species. These enzymes were inhibited in a competitive manner. The HSV-induced DNA-dependent DNA polymerase was 39-fold more sensitive to ara-ATP than was cellular DNA polymerase-beta and 116-fold more sensitive than cellular DNA polymerase-alpha. The affinity of the HSV-induced enzyme for ara-AT…
Yeast interaction on Chardonnay wine composition: Impact of strain and inoculation time.
2022
Abstract It is of great importance to understand the molecular characteristics and substantial chemical transformations due to yeast-yeast interaction. Non-targeted metabolomics was used to unravel must in fermentation composition, inoculated with non-Saccharomyces (NS) yeasts and Saccharomyces cerevisiae (S) for sequential fermentation. ultrahigh-resolution mass spectrometry was able to distinguish thousands of metabolites and provides deep insights into grape must composition allowing better understanding of the yeast-yeast interactome. The dominance of S, characterized by a metabolic richness not found with NS, is dependent on inoculation time and on the yeast species present. Co-inocula…
Formation of arynezirconocenes from substituted diaryl bis (t-butylcyclopentadienyl) zirconium: application to the synthesis of new functionalizedort…
1991
The para-substituted diphenylzirconocenes [(t-BuCp)2Zr(p-C6H4R)2; R = Br, NMe2] (A) were easily obtained from the reaction of the appropriate organolithium reagent with bis(t-butylcyclopentadienyl)zirconium dichloride. Elimination of bromobenzene or N,N-dimethylaminobenzene from A by slight heating led to arynezirconocenes into which were inserted two equivalents of elementary chalcogens. As a result dichalcogenated zirconacycles [(t-BuCp)2ZrY2C6H3R; Y = S, Se] (B) were obtained. Complexes B constitute useful potential synthons in organic synthesis and a large family of new functionalized dichalcogenated benzenic compounds was prepared by reacting electrophiles. The structure of complexes B…
Enantioselective Synthesis of Substituted Indoles Through Zirconium(IV)-Catalyzed Friedel–Crafts Alkylation
2012
The chiral complex of ( R )-3,3′-Br 2 -BINOL and zirconium tert -butoxide catalyzes the Friedel–Crafts alkylation of indoles with enones bearing an alkyl or fluorinated group at the β-position to give indoles having a side chain at the C3 position with a tertiary stereogenic center in good yields and with excellent enantioselectivities.
Revisiting delta-6 desaturase regulation by C18 unsaturated fatty acids, depending on the nutritional status.
2009
Dietary polyunsaturated fatty acids (PUFA) play a key role in regulating delta-6 desaturase (D6D), the key enzyme for long-chain PUFA biosynthesis. Nevertheless, the extent of their effects on this enzyme remains controversial and difficult to assess. It has been generally admitted that C18 unsaturated fatty acids (UFAs) regulate negatively delta-6 desaturase (D6D). This inhibition has been evidenced in regard to a high glucose/fat free (HG/FF) diet used in reference. However, several nutritional investigations did not evidence any inhibition of desaturases when feeding fatty acids. Because the choice of the basal diet appeared to be of primary importance in such experiments, our goal was t…
Herbicidally Active Derivatives of Aminomethylenebis-Phosphonic Acid-Mode of Action and Structure - Activity Relationship
1996
Abstract: (N-pyridylamino)methylenebisphosphonates exhibit strong herbicidal activity which may be reversed by supplementation of the growth media with aromatic amino acids. They appeare to be the inhibitors of aromatic amino acids biosynthesis acting as inhibitors of DAHP synthase the first enzyme of shikimate pathway. Over 40 analogues of these acids were synthesized in order to determine the structure-activity relationship.