Search results for "DERIVATIVES"

Photochemistry of Fluorinated Heterocyclic Compounds. An Expedient Route for the Synthesis of Fluorinated 1,3,4-Oxadiazoles and 1,2,4-Triazoles

2004

The photochemistry of some 3-N-alkylamino-5-perfluoroalkyl-1,2,4-oxadiazoles in the presence of nitrogen nucleophiles such as ammonia and primary and secondary aliphatic amines has been investigated. The primary photolytic intermediate from the cleavage of the ring O-N bond follows two distinct and competing pathways leading to (i). 5-perfluoroalkyl-1,3,4-oxadiazoles, through the ring contraction-ring expansion photoisomerization route favored by the presence of the base or (ii). 5-perfluoroalkyl-1,2,4-triazoles, through the intervention, as an internal nucleophile, of the exocyclic N-alkylamino moiety of the oxadiazole followed by the attack of the external nitrogen nucleophile and subsequ…

Synthesis, Reactivity and Theoretical Study of B3H8−and Related Derivatives

1996

Abstract Octahydrotriborate salts, B3H8 −, have been prepared by the reaction of NaBH4 with Lewis acids such as BX3·BDMA (BDMA = benzyldimethylamine, × = Cl,Br) or C2H5I in diglyme. The presence of BH3·BDMA as a by-product in the former reaction provides new insight into the reaction mechanism of B11H14 − formation. In acetonitrile-water solutions of HCl or CH3CO2H, the B3H8 − anion reacted to give B3H7CH3CN or B3H7CH3CO2 − characterized by 11B NMR spectroscopy. Their kinetic hydrolysis study was consistent with NMR analysis. Reaction of Bu4NB3H8 and CuCl2 at 0°C produced pure B3H6Cl2 −. An AM1 theoretical study of the substituted derivatives B3H7L (L = Cl−, CH3CN, CH3CO2 −, OH−) and B3H6L2…

Electrical transduction in phthalocyanine-based gas sensors: from classical chemiresistors to new functional structures

2009

Phthalocyanines are organic-based materials which have attracted a lot of research in recent times. In the field of sensors, they present interesting and valuable potentialities as sensing elements for real gas sensor applications. In the present article, and taking some of our experiments as representative examples, we review the different ways of transduction applied to such applications. Some of the new tendencies and transducers for gas sensing based on phthalocyanine derivatives are also reported. Among them, electrical transduction (resistors, field-effect transistors, diodes, etc.) has been, historically, the most commonly exploited way for the detection and/or quantification of gas…

ChemInform Abstract: Synthesis of Five-Membered Nitrogen Heterocycles from Iron-Substituted Enals: Novel Insight into the η5-Cyclopentadienyl(dicarbo…

2010

Effect of fluid resuscitation on cerebral integrity: A prospective randomised porcine study of haemorrhagic shock.

2021

BACKGROUND The treatment of haemorrhagic shock is a challenging task. Colloids have been regarded as standard treatment, but their safety and benefit have been the subject of controversial debates. Negative effects, including renal failure and increased mortality, have resulted in restrictions on their administration. The cerebral effects of different infusion regimens are largely unknown. OBJECTIVES The current study investigated the impact of gelatine-polysuccinate, hydroxyethyl starch (HES) and balanced electrolyte solution (BES) on cerebral integrity, focusing on cerebral inflammation, apoptosis and blood flow in pigs. DESIGN Randomised experimental study. SETTING University-affiliated …

Free radical scavenging abilities of flavonoids as mechanism of protection against mutagenicity induced by tert-butyl hydroperoxide or cumene hydrope…

2003

Mutagenicity induced by tert-butyl hydroperoxide (BHP) or cumene hydroperoxide (CHP) in Salmonella typhimurium TA102 was effectively reduced by flavonols with 3',4'-hydroxyl groups such as fisetin, quercetin, rutin, isoquercitrin, hyperoxide, myricetin, myricitrin, robinetin, and to a lesser extent also by morin and kaempferol (ID50=0.25-1.05 micromol per plate). With the exception of isorhamnetin, rhamnetin, morin, and kaempferol, closely similar results were obtained with both peroxides. Hydrogenation of the double bond between carbons 2 and 3 (dihydroquercetin, dihydrorobinetin) as well as the additional elimination of the carbonyl function at carbon 4 (catechins) resulted in a loss of a…

(S)-2-[(2-Hydroxybenzyl)azaniumyl]-4-(methylsulfanyl)butanoate

2011

The zwitterionic title compound, C12H17NO3S, is a reduced Schiff base derived from (S)-N-(2-hydroxybenzylidene)methionine. An intramolecular interaction between the N—H and carboxylate groups forms a roughly planar (r.m.s. deviation = 0.1405 Å) five-membered ring containing the H(N), N, Cα, C(carboxylate) and O atoms in a pentagonal conformation. In the crystal, a supramolecular triangle-shaped motif is generated by molecules held together by O—H...O and N—H...O hydrogen bonds.

Marine inspired antiplasmodial thiazinoquinones: synthesis, computational studies and electrochemical assays

2015

In the search for new antimalarials, we used the quinone scaffold of marine secondary metabolites as a chemical starting point to synthesize new thiazinoquinone compounds. Most of synthetic derivatives have shown a significant pharmacological activity and some structural requirements, critical for both the antiplasmodial effect and cytotoxicity, have been evidenced. The redox properties of the prepared compounds have been investigated by computational studies and electrochemical assays, which indicated that a higher antiplasmodial activity of some thiazinoquinones is related to their greater ability to form the semiquinone species and strongly interact with free Fe(III)-protoporphyrin IX.

SINGLE FACTOR STOCHASTIC MODELS WITH SEASONALITY APPLIED TO UNDERLYING WEATHER DERIVATIVES VARIABLES

2003

This paper estimates single factor stochastic models describing daily air temperature behaviour. We modify classical financial models to reflect temperature seasonality and fit them to a time series representing temperatures in Spain. The estimated models are used in Montecarlo simulations to obtain heating and cooling degree-days, which are used as an underlying reference in weather derivatives. The final goal of this work is to obtain an insight into weather derivative valuation, and so making it easier to manage economic activity risks closely related to temperature (i.e. oil, gas and electricity prices and volumes). En este trabajo se estiman modelos estocásticos unifactoriales que desc…

Novel bioactive bromopyrrole alkaloids from the Mediterranean sponge Axinella verrucosa

2005

The Mediterranean sponge Axinella verrucosa has been investigated for its alkaloid composition and has been found to produce a complex mixture of bromopyrrole alkaloids. Along with the previously isolated compounds 5-18, four novel alkaloids of this class, compounds 1-4, have been isolated, and their structures established through spectroscopic methods. Compounds 1-4 were found to display neuroprotective activity against the agonists serotonin and glutamate in vitro.