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

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

Synthesis of 2,3-dihydro-1,4-dithiinyl nucleosides via pummerer-type glycosidation

A straightforward procedure for the preparation of nucleoside analogue 1 and its regioisomer 2 containing a dihydro-1,4-dithiin as sugar moiety has been accomplished in four steps by our readily available heterocyclic system 5. Nucleobase insertion was carried out by direct addition of N4-acetylcytosine to sulfoxide derivatives via Pummerer-type glycosidation reaction

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

Stereoselective Synthesis of Selenium-Containing Glycoconjugates via the Mitsunobu Reaction

A simple and efficient route for the synthesis of new glycoconjugates has been developed.The approach acts as a model for a mini-library of compounds with a deoxy-selenosugar core joinedto a polyphenolic moiety with well-known antioxidant properties. An unexpected stereocontroldetected in the Mitsunobu key reaction led to the most attractive product showing a natural Dconfiguration. Thus, we were able to obtain the target molecules from the commercially availableD-ribose via a shorter and convenient sequence of reaction

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

Ecotoxic effects of loratadine and its metabolic and light-induced derivatives

Loratadine and desloratadine are second-generation antihistaminic drugs. Because of human administration, they are continuously released via excreta into wastewater treatment plants and occur in surface waters as residues and transformation products (TPs). Loratadine and desloratadine residues have been found at very low concentrations (ng/L) in the aquatic environment but their toxic effects are still not well known. Both drugs are light-sensitive even under environmentally simulated conditions and some of the photoproducts have been isolated and characterized. The aim of the present study was to investigate the acute and chronic ecotoxicity of loratadine, desloratadine and their light-induced transformation products in organisms of the aquatic trophic chain. Bioassays were performed in the alga Pseudokirchneriella subcapitata, the rotifer Brachionus calyciflorus and in two crustaceans, Thamnocephalus platyurus and Ceriodaphnia dubia. Loratadine exerted its acute and chronic toxicity especially on Ceriodaphnia dubia (LC50: 600 mu g/L, EC50: 28.14 mu g/L) while desloratadine showed similar acute toxicity among the organisms tested and it was the most chronically effective compound in Ceriodaphnia dubia and Pseudokirchneriella subcapitata. Generally, transformation products were less active in both acute and chronic assays.Peer reviewe