104 research outputs found
Dye-sensitized Photooxygenation of furanosyl Furans; Synthesis of a new Pyridazine C-Nucleoside
The dye-sensitized photooxygenation of furanosyl furans easily affords C- or O-glycosides with cis-R,-unsaturated 1,4-dioxo aglycones. The reaction, performed on a ribofuranosyl furan, provides a useful new entry to a novel pyridazine C-nucleoside that can be achieved through a simple one-pot procedure
Unusual products of the aqueous chlorination of atenolol
The reaction
of the drug atenolol
with hypochlorite
under conditions
that simulate
wastewater
disinfection
was investigated.
The pharmaceutical
reacted in 1 h yielding
three products
that were
separated
by chromatographic
techniques
and characterized
by spectroscopic
features.
Two unusual
products
2-(4-(3-(chloro(2-chloropropan-
2-yl)amino)-2-hydroxypropoxy)
phenyl) acetamide
and 2-(4-
(3-formamido-
2-hydroxypropoxy)
phenyl) acetamide
were obtained along with 2-(4-hydroxyphenyl)
acetamide.
When the reaction
was stopped at shorter times only 2-(4-(3-amino-2-hydroxypropoxy)
phenyl) acetamide
and the dichlorinated
product
were detected. Tests performed
on the seeds of
Lactuca
sativa
show that chlorinated
products
have phytotoxic
activity
Degradation of lansoprazole and omeprazole in the aquatic environment
Lansoprazole and omeprazole degrade in water leading to sulfides, benzimidazolones and a red complex material.
Degradation is accelerated in acid medium and by solar simulator irradiation. Benzimidazoles, dianilines and pyridines
have also been identified
A mechanistic study on the phototoxicity of atorvastatin: singlet oxygen generation by a phenanthrene-like photoproduct
Atorvastatin calcium (ATV) is one of the most frequently prescribed drugs worldwide. Among the
adverse effects observed for this lipid-lowering agent, clinical cases of cutaneous adverse reactions have
been reported and associated with photosensitivity disorders. Previous work dealing with ATV
photochemistry has shown that exposure to natural sunlight in aqueous solution leads to photoproducts
resulting from oxidation of the pyrrole ring and from cyclization to a phenanthrene derivative. Laser
flash photolysis of ATV, at both 266 and 308 nm, led to a transient spectrum with two maxima at λ )
360 and λ ) 580 nm (τ ) 41 μs), which was assigned to the primary intermediate of the stilbene-like
photocyclization. On the basis of the absence of a triplet-triplet absorption, the role of the parent drug
as singlet oxygen photosensitizer can be discarded. By contrast, a stable phenanthrene-like photoproduct
would be a good candidate to play this role. Laser flash photolysis of this compound showed a triplet-triplet
transient absorption at λmax ) 460 nm with a lifetime of 26 μs, which was efficiently quenched by
oxygen (kq ) 3 ((0.2) Ă— 109 M-1 s-1). Its potential to photosensitize formation of singlet oxygen was
confirmed by spin trapping experiments, through conversion of TEMP to the stable free radical TEMPO.
The photoreactivity of the phenanthrene-like photoproduct was investigated using Trp as a marker. The
disappearance of the amino acid fluorescence (λmax ) 340 nm) after increasing irradiation times at 355
nm was taken as a measurement of photodynamic oxidation. To confirm the involvement of a type II mechanism, the same experiment was also performed in D2O; this resulted in a significant enhancement of the reaction rate. On the basis of the obtained photophysical and photochemical results, the phototoxicity of atorvastatin can be attributed to singlet oxygen formation with the phenanthrene-like photoproduct as
a photosensitizer
Photochemical behavior of the drug atorvastatin in water.
Atorvastatin undergoes a self-sensitized photooxygenation by sunlight in water. The main photoproducts, isolated by chromatographic
techniques, have been identified by spectroscopic means. They present a lactam ring arising from an oxidation of pyrrole ring and an
alkyl/aryl shift. A mechanism involving singlet oxygen addition and an epoxide intermediate is suggested
Photooxygenation of furans in water and ionic liquid solutions
Photooxygenation of differently functionalized furans is investigated in aqueous solutions and in
ionic liquids [emim]Br and [bmim]BF4. The reaction is generally selective and the final products
derive from rearrangement of the intermediate endoperoxides, depending mainly on the polarity
and/or nucleophilic nature of the solvent
Phototransformation Products of Tamoxifen by Sunlight in Water. Toxicity of the Drug and Its Derivatives on Aquatic Organisms
Transformation of tamoxifen has been observed in water by prolonged sunlight irradiation. The main photoproducts, isolated by
chromatographic techniques, have been identified by spectroscopic means. Photoisomerization, photocyclization and, to a lesser extent,
photooxygenation appear to be involved in the degradation of the drug. The acute and chronic toxicity of the parent drug and its photoproducts
were tested on non-target aquatic organisms (Brachionus calyciflorus, Thamnocephalus platyurus, Daphnia magna and Ceriodaphnia
dubia). Exposure to all the compounds induced mainly chronic effects without significant differences among the parental and
derivative compounds
A one-pot approach to novel pyridazine c-nucleosides
The synthesis of glycosides and modified nucleosides represents a wide research field in organic chemistry. The classical methodology is based on coupling reactions between a glycosyl donor and an acceptor. An alternative strategy for new C-nucleosides is used in this approach, which consists of modifying a pre-existent furyl aglycone. This approach is applied to obtain novel pyridazine C-nucleosides starting with 2-and 3-(ribofuranosyl)furans. It is based on singlet oxygen [4+2] cycloaddition followed by reduction and hydrazine cyclization under neutral conditions. The mild three-step one-pot procedure leads stereoselectively to novel pyridazine C-nucleosides of pharmacological interest. The use of acetyls as protecting groups provides an elegant direct route to a deprotected new pyridazine C-nucleoside
Transformation and Ecotoxicity of Carbamic Pesticides in Water
N-methylcarbamate insecticides are widely used chemicals for crop protection. This study examines the hydro- lytic and photolytic cleavage of benfuracarb, carbosulfan and carbofuran under natural conditions. Their toxicity and that of the corresponding main degradation products toward aquatic organisms were evaluated.
Suspensions of benfuracarb, carbosulfan and carbo- furan in water were exposed to sunlight, with one set of dark controls, for 6 days, and analyzed by 1H-NMR and HPLC. Acute toxicity tests were performed on Brachionus calyciflorus, Daphnia magna, and Thamnocefalus platyurus. Chronic tests were performed on Pseudokirchneriella subcapitata, and Cerio- daphnia dubia.
Under sunlight irradiation, benfuracarb and carbosulfan gave off carbofuran and carbofuran-phenol, while only carbofuran was detected in the dark experiments. The latter was degraded to phenol by exposure to sunlight. Ef- fects of pH, humic acid and KNO3 were evaluated by kinetics on dilute solutions in the dark and by UV irradiation, which evidenced the lability of the pesticide at pH 9. All three pesti- cides and phenol exhibited acute and higher chronic toxicity towards the aquatic organisms tested.
Investigation on the hydrolysis and photolysis of benfuracarb and carbosulfan under natural conditions provides evidence concerning the selective decay to carbofuran and/or phenol. Carbofuran is found to be more persistent and toxic.
The decay of benfuracarb and carbosulfan to carbofuran and the relative stability of this latter pesticide account for many papers that report the detection of carbofuran in water, fruits and vegetables
Photochemical Behaviour of Carbamates Structurally Related to Herbicides in Aqueous Media: Nucleophilic Solvent Trapping versus Radical Reactions
Irradiation ofN-arylO-aryl carbamates has been carried out in H2O/CH3CN (1 : 1 v/v) solutions atλ>290 nm. When chlorine is on theN-aryl ring, halogen-substituted products are found. These photoproducts derive from the trapping of the intermediate radical cation by water and, even, by acetonitrile leading to phenols andN-arylacetamides (photo-Ritter products), respectively. UnsubstitutedN-aryl carbamates slowly undergo photo-Fries reaction
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