Andrea D'Annibale

Lactonization of Olefins Mediated by Mn(OAc)3: A Sonochemical Approach.

Abstract The reaction of lactonization of olefins with carboxyalkyl radicals and Mn(OAc) 3 was carried out under ultrasound irradiation at low temperatures. Good yields of lactones were obtained in short reaction times. In sonochemical conditions, reoxidation of Mn(II) occurred, allowing the development of a lactonization procedure with a catalytic amount of Mn(III).

Mn(III) — promoted cyclization of enamides: An oxidative radical approach to β-lactams

α-Caibomethoxy-N-vinylamides were reacted with Mn(OAc)3 in glacial acetic acid at 70 °C to afford variously substituted β-lactams in good yields and short reaction times.

Oxidation of diphenyl diselenide with ceric ammonium nitrate: a Novel route for functionalization of olefins

Abstract Alkenes were reacted with diphenyl diselenide in presence of ceric ammonium nitrate in methanol, affording β-methoxyalkyl phenyl selenides in good yields.

Mixed hybrid bilayer lipid membrane incorporating valinomycin: Improvements in preparation and functioning

The paper deals with the reconstruction of lipid bilayer membranes on a Au-covered polycarbonate membrane. Such a kind of like-biomembranes (namely mixed hybrid bilayer lipid membrane (MHBLM)) are characterised by appreciable long-term stability. Here we describe changes that have been made in the geometry of the experimental device in order to avoid artefacts and render membrane reproduction easier. Incorporation of valinomycin was performed to check the membrane and its stability: conductance and membrane potential following the changes of ion concentration were recorded. This new approach permits increase of successful trials and renders possible, when it breaks, easily formation of a new MHBLM on the same Au-covered polycarbonate membrane support. Finally, the stability shown by the MHBLM renders this system a promising tool for use under flowing conditions.

Manganese(III)-promoted free radical cyclizations of enamides leading to β-Lactams

Abstract Reaction of variously substituted enamides with Mn(OAc)3·2H2O afforded β-lactamic products in modest to good yields, depending mostly on the solvent and reaction conditions. The substitution pattern of the enamidic double bond was found of primary importance for the outcome of the reaction.

Sugar-Bile Acid-Based Bolaamphiphiles: From Scrolls to Monodisperse Single-Walled Tubules.

The introduction of a mannose residue on carbon 3 of lithocholic acid gives rise to an asymmetric and rigid bolaamphiphilic molecule, which self-assembles in water to form elongated tubular aggregates with an outer diameter of about 20 nm. These tubular structures display a temporal evolution, where the average tube diameter decreases with time, which can be followed by time-resolved small-angle X-ray scattering experiments. Cryogenic transmission electron microscopy images collected as a function of time show that at short times after preparation tubular scrolls are formed via the rolling of layers, after which a complex transformation of the scrolls into single-walled tubules takes place. At long time scales, a further evolution occurs where the tubules both elongate and become narrower. The observed self-assembly confirms the tendency of bile acids and their derivatives to form supramolecular aggregates with an ordered packing of the constituent molecules. It also demonstrates that scrolls can be formed as intermediate structures in the self-assembly process of monodisperse single-walled tubules.

Ferrocenyl Alkanethiols−Thio β-Cyclodextrin Mixed Self-Assembled Monolayers: Evidence of Ferrocene Electron Shuttling Through the β-Cyclodextrin Cavity

This paper reports the preparation and characterization of an Au electrode modified with self-assembled alkane ferrocenes, in the absence and in the presence of beta-cyclodextrins (betaCD). Electrode modification with ferrocene derivatives was achieved through a self-assembled monolayer (SAM) approach, using ferrocenyl hexane thiol (FcC6) and ferrocenyl undecane thiol (FcC11); the same was also done using per-6-thio-beta-cyclodextrin. The different SAMs prepared were characterized by both cyclic voltammetry and electrochemical surface plasmon resonance (EC-SPR). The behavior of both single and binary monolayers including their interfacial reorganization was investigated and critically discussed, according to the nature of the SAM used. Cyclic voltammetry combined with SPR measurements revealed the reorientation of the SAM concomitant with the oxidation of ferrocene moieties. In particular, the electron shuttling of FcC11 through the betaCD cavity (mixed SAM) was also evidenced by both SPR and the electrocatalytic oxidation of ferro(II)cyanide.

Mn(III)-promoted sulfur-directed 4-exo-trig radical cyclization of Enamides to β-lactams☆

Abstract The synthesis of β-lactams vinylated at C-4 from N-(3-phenylthio-1-alkenyl)amides was carried out by Mn(III)-promoted 4-exo-trig radical cyclization followed by β-fragmentative loss of phenylthiyl radical. The effects on the reaction course of different substituents both on enamidic nitrogen atom or double bond were analyzed. The overall reaction was stereoselective, leading to trans azetidinones.

Between peptides and bile acids: self-assembly of phenylalanine substituted cholic acids.

Biocompatible molecules that undergo self-assembly are of high importance in biological and medical applications of nanoscience. Peptides and bile acids are among the most investigated due to their ability to self-organize into many different, often stimuli-sensitive, supramolecular structures. With the aim of preparing molecules mixing the aggregation properties of bile acid and amino acid-based molecules, we report on the synthesis and self-association behavior of two diastereomers obtained by substituting a hydroxyl group of cholic acid with a l-phenylalanine residue. The obtained molecules are amphoteric, and we demonstrate that they show a pH-dependent self-assembly. Both molecules aggregate in globular micelles at high pH, whereas they form tubular superstructures under acid conditions. Unusual narrow nanotubes with outer and inner cross-section diameters of about 6 and 3 nm are formed by the derivatives. The diasteroisomer with α orientation of the substituent forms in addition a wider tubule (17 nm cross-section diameter). The ability to pack in supramolecular tubules is explained in terms of a wedge-shaped bola-form structure of the derivatives. Parallel or antiparallel face-to-face dimers are hypothesized as fundamental building blocks for the formation of the narrow and wide nanotubes, respectively.

Ceric ammonium nitrate promoted free radical cyclization reactions leading to β-lactams

The reaction of enamides with CAN in methanol affords variously functionalized β-lactams through a 4-exo-trig cyclization of α-carbamoylalkyl radicals; in most cases products with trans stereochemistry can be obtained.