Search results for "Alkyl"
showing 10 items of 928 documents
One-Pot Synthesis to Quinone-Based Diaza[3.3]cyclophanes
2017
A simple one-pot synthesis to [3.3]cyclophanes that involves quinone moieties was found. The protocol tolerates a variety of amines that include aliphatic and aromatic structures with different functional groups, such as hydroxy groups, amides, and terminal double and triple bonds. The straightforward synthesis can be performed by a twofold N-alkylation reaction with 2,5-bis(bromomethyl)-3,6-dimethyl-1,4-benzoquinone (1). Neither anhydrous nor inert conditions are required. Various amines can be employed without any activating groups, several functionalities at end groups are tolerated, and the cyclophanes generated can be easily modified or embedded into larger molecular architectures. The…
Light-Induced Alkylation of (Hetero)aromatic Nitriles in a Transition-Metal-Free C–C-Bond Metathesis
2017
A light-induced C–C-σ-bond metathesis was achieved through transition-metal-free activation of an unstrained C(sp3)–C(sp3)-σ-bond in 1-benzyl-1,2,3,4-tetrahydroisoquinolines. A photoredox-mediated single-electron oxidation of these precursor amines yield radical cations which undergo a homolytic cleavage of a C(sp3)–C(sp3)-σ-bond rather than the well-known α-C–H-scission. The resulting carbon-centered radicals are used in the ipso-substitution of (hetero)aromatic nitriles proceeding through another single-electron transfer-mediated C–C-bond cleavage and formation.
A reinvestigation of compound CpMo(PMe3)2(CH3)2: Alkylation by single electron transfer and radical addition?
2001
International audience; The synthesis of the half-sandwich molybdenum(III) diphosphine dimethyl complex CpMo(PMe3)2(CH3)2 has been reinvestigated. The compound was obtained from the corresponding dichloro complex CpMo(PMe3)2Cl2 and methyllithium at low temperatures and isolated as a crystalline product by conducting all operations at temperatures lower than −10 °C. The complex is thermally unstable at room temperature but has been fully characterised by EPR spectroscopy, cyclic voltammetry and X-ray diffraction. The formation reaction is retarded by excess phosphine. On the basis of this and other related observations, a mechanism involving phosphine pre-dissociation followed by single elec…
Melatonin in the seasonal response of the aphid Acyrthosiphon pisum.
2018
Aphids display life cycles largely determined by the photoperiod. During the warm long-day seasons, most aphid species reproduce by viviparous parthenogenesis. The shortening of the photoperiod in autumn induces a switch to sexual reproduction. Males and sexual females mate to produce overwintering resistant eggs. In addition to this full life cycle (holocycle), there are anholocyclic lineages that do not respond to changes in photoperiod and reproduce continuously by parthenogenesis. The molecular or hormonal events that trigger the seasonal response (i.e., induction of the sexual phenotypes) are still unknown. Although circadian synthesis of melatonin is known to play a key role in verteb…
Application of hydrolases and probiotic Pediococcus acidilactici BaltBio01 strain for cereal by-products conversion to bioproduct for food/feed
2017
The aim of this study was to apply the enzymatic treatment and fermentation by Pediococcus acidilactici BaltBio01 strain for industrial cereal by-products conversion to food/feed bioproducts with high amount of probiotic lactic acid bacteria (LAB). LAB propagated in potato media and spray-dried remained viable during 12months (7.0 log10 cfu/g) of storage and was used as a starter for cereal by-products fermentation. The changes of microbial profile, biogenic amines (BAs), mycotoxins, lactic acid (Lþ/D), lignans and alkylresorcinols (ARs) contents in fermented cereal by-product were analysed. Cereal by-products enzymatic hydrolysis before fermentation allows to obtain a higher count of LAB d…
Behaviour of alkyl oleates following foliar application in relation to their influence on the penetration of phenmedipham and quizalofop-P-ethyl
1997
Summary The foliar penetration of four alkyl oleates (methyl to butyl) and their influence on the penetration of phenmedipham and quizalofop-P-ethyl was studied in barley (Hordeum vulgare L.), cleavers (Galium aparine L.) and pea (Pisum sativum L.). Loss of alkyl oleates from glass and plant surfaces was inversely related to the length of the alkyl chains and was assumed to be due to volatilization. All four alkyl oleates after application alone, readily penetrated into pea and barley leaves but much less into G. aparine. Penetration of methyl oleate appeared to be faster than that of butyl oleate. Both alkyl oleates were completely metabolized in barley and pea in 27 h, but not in G. apari…
Arabidopsis thaliana nicotianamine synthase 4 is required for proper response to iron deficiency and to cadmium exposure.
2013
International audience; The nicotianamine synthase (NAS) enzymes catalyze the formation of nicotianamine (NA), a non-proteinogenic amino acid involved in iron homeostasis. We undertook the functional characterization of AtNAS4, the fourth member of the Arabidopsis thaliana NAS gene family. A mutant carrying a T-DNA insertion in AtNAS4 (atnas4), as well as lines overexpressing AtNAS4 both in the atnas4 and the wild-type genetic backgrounds, were used to decipher the role of AtNAS4 in NA synthesis, iron homeostasis and the plant response to iron deficiency or cadmium supply. We showed that AtNAS4 is an important source for NA. Whereas atnas4 had normal growth in iron-sufficient medium, it dis…
Characterization of Purified Green Bell Pepper Hydroperoxide Lyase Expressed by Yarrowia Lipolytica: Radicals Detection during Catalysis
2007
International audience; The optimization of the expression of recombinant 6-His-tagged HPO lyase in Yarrowia lipolytica is described: 1800U/L of culture was detected at 24h of culture on a medium containing olive oil as the sole carbon source. The enzyme was purified by IMAC and showed an optimal pH at 5.5, an optimal temperature at 20^\circC and a Km value of 9μM with 13-HPOD substrate. The participation of radicals during the catalysis of purified bell pepper fruit hydroperoxide lyase has been observed by electron paramagnetic resonance spectroscopy and the yet unidentified radical species might be an alkyl or alkoxyl radical linked to the enzyme.
Changes of bioactive compounds in barley industry by‐products during submerged and solid state fermentation with antimicrobial Pediococcus acidilacti…
2019
Abstract In this study, changes of bioactive compounds (crude protein (CP), crude fat (CF), dietary fiber (DF), fatty acids (FAs), free amino acids (FAAs), phenolic compounds (PCs), biogenic amines (BAs), lignans, and alkylresorcinols) in barley industry by‐products (BB) during submerged and solid state fermentation (SSF) with Pediococcus acidilactici were analyzed. It was established that both fermentation conditions reduce the CP and CF content in BB (by 25.8% and 35.9%, respectively) and increase DF content (on average by 25.0%). Fermentation increases the oleic, arachidic, eicosadienoic, behenic, and lignoceric FA in BB samples. The highest total BA content was found in untreated sample…
Embryonic Growth of Face-Center-Cubic Silver Nanoclusters Shaped in Nearly Perfect Half-Cubes and Cubes.
2016
Demonstrated herein are the preparation and crystallographic characterization of the family of fcc silver nanoclusters from Nichol’s cube to Rubik’s cube and beyond via ligand-control (thiolates and phosphines in this case). The basic building block is our previously reported fcc cluster [Ag14(SPhF2)12(PPh3)8] (1). The metal frameworks of [Ag38(SPhF2)26(PR′3)8] (22) and [Ag63(SPhF2)36(PR′3)8]+ (23), where HSPhF2 = 3,4-difluorothiophenol and R′ = alkyl/aryl, are composed of 2 × 2 = 4 and 2 × 2 × 2 = 8 metal cubes of 1, respectively. All serial clusters share similar surface structural features. The thiolate ligands cap the six faces and the 12 edges of the cube (or half cube) while the phosp…