OsO4-catalyzed oxidative cyclization of geranyl and neryl acetate to cis-2,5-bis(hydroxymethyl)tetrahydrofurans

OsO4 catalyzes the oxidative cyclization of the 1,5-dienes geranyl acetate, (E)-Me2CH:CH(CH2)2CMe:CHCH2OAc (I), and neryl acetate, (Z)-Me2CH:CH(CH2)2CMe:CHCH2OAc (II), to the cis-2,5-bis(hydroxymethyl)tetrahydrofurans III and IV, resp., in the presence of NaIO4 as cooxidant in DMF. The reaction is stereospecific and proceeds with the sequential syn addn. to both double bonds of the starting materials. The observed stereoselectivity can be explained by invoking the intermediacy of a square-based pyramidal osmium (VI) diester V that has been isolated and characterized. Evidence is reported that this substance is indeed an intermediate in the transformation of I to III

Glycomimetics as decorating motifs for oligonucleotides: solid phase synthesis, stability and hybridization properties of carbopeptoid-oligonucleotide conjugates

The online solid-phase synthesis of oligonucleotides conjugated at the 3' end with [1-6]-linked oligosaccharide mimics having the O-glycosidic linkages replaced by amide bonds is here described. The assembly of the carbohydrate domain has been carried out by exploiting classical solid phase peptide synthetic protocols, starting from solid supports functionalized with 1-azido sugars, in association with suitably protected 1-azido uronic acids of glucose and lactose, chosen as model addition monomers. After the insertion of a flexible linker, elongation of the oligodeoxyribonucleotide (ODN) chain was performed by standard automated phosphoramidite protocols. 3'-Glycoconjugated 18-mers exhibited an increased enzymatic stability with respect to the same unmodified ODN sequence. UV thermal denaturation experiments showed that the presence of the oligosaccharide tail at the 3' end of the oligonucleotides did not negatively interfere with their duplex formation abilities

New nucleoside based solid supports. Synthesis of 5’,3’-derivatized thymidine analogues

Two new thymidine based polymeric supports, in which the nucleosides have been anchored through the thymine moiety to a β-hydroxy thioether functionalized resin via a Mitsunobu reaction, have been prepared. A simple and efficient solid-phase synthesis of 5′,3′-bis-derivatized thymidine analogues has so been developed, following methodologies well established in peptide and oligonucleotide chemistry and is here proposed for the preparation of a variety of different nucleoside conjugate products

New solid supports linking nucleoside scaffolds

An easy and efficient strategy to obtain new nucleoside based solid supports in which the nucleoside moieties have been anchored to the solid support through the nucleobase is here proposed. A simple and efficient solid-phase synthesis of 5′ and 3′-derivatized uridine analogues has so been developed, following methodologies well established in organic chemistry

Antibiotics in the environment: occurrence in Italian STPs, fate and preliminary assessment on algal toxicity of amoxicillin.

Amoxicillin is a widely used penicillin-like antibiotic, and due to its presence in several effluents of ItalianSTPs, its environmental fate along with its toxicity toward simple organisms have been investigated in model conditions. The present study shows that under abiotic conditions both hydrolysis and direct photolysis could be responsible for the transformation and removal of amoxicillin in aquatic environment, especially in slightly basic media. Quantum yields for the solar direct photolysis have been calculated along with kinetic constants and half-life times. Indirect photolysis experiments in the presence of natural photosensitizers such as nitrate ions and humic acids indicate that nitrate ions have no influence on the photodegradation rate of amoxicillin, while humic acids are able to enhance it. Standard batch experiments have been also performed under biotic conditions. The results indicated that also biodegradation on activated sludge is an effective pathway through which amoxicillin can be removed from the aquatic environment. Rate constants for biodegradation and adsorption have been calculated by applying simple pseudo-first-order kinetic models. Algal bioassays indicate that, in the range of concentrations from 50 ng/L to 50 mg/L, amoxicillin is not toxic toward eucariotic organisms such as the ChlorophyceaePseudokirkneriella subcapitata and Closterium ehrenbergii and the BacillariophyceaeCyclotella meneghiniana, but it shows a marked toxicity toward the CyanophytaSynechococcus leopolensis