Andrea Bomben

A new synthesis of 2-aryloxypropionic acids derivatives via selective mono-c-methylation of methyl aryloxyacetates and aryloxyacetonitriles with dimethyl carbonate

Abstract A one-pot procedure for the mono-C-methylation of methyl aryloxyacetates and aryloxyaceto nitnles by dimethyl carbonate (DMC) is reported The reaction is earned out in an autoclave at high temperatures (180–200 ° C) and in the presence of a base (K 2 CO 3 or bart -BuOK). Although DMC is used either as the alkylating agent or as the solvent (30 molar excess with respect to the substrates). The selectivity towards the mono-methylated products (methyl 2-aryloxypropionates and 2-aryloxypropio nitnles, respectively) is typically up to 99%, at complete conversion; no dialkylated by-products form. The reasons of such an unusual behaviour is explained by a mechanism involving an initial carboxymethylation followed by a methylation reaction.

Selective mono-N-methylation of primary aromatic amines by dimethylcarbonate over faujasite X- and Y-type zeolites

The reaction of dimethyl carbonate (DMC) with different primary aromatic amines has been investigated under batch conditions (autoclave) in the presence of Y- and X-type zeolites. Operating at 120–150 °C, highly selective mono-N-methylations are observed for anilines even when they are deactivated by either electronic effects or steric hindrance (G–C6H4NH2, G = p-NO2, p-CN, o-CO2CH3 and 2,6-dimethylaniline); typical selectivities for the formation of the corresponding mono-N-methyl derivatives [ArNH(CH3)] are in the range 92–98%, at a substrate conversion of 72–93%. A synergic effect between the reactivity of DMC (acting both as a methylating and as a reversible methoxycarbonylating agent) and the dual acid–base properties of zeolites is considered to be responsible for the unusually high selectivity observed; accordingly, a reaction mechanism is discussed, involving carbamates (ArNHCO2CH3) and N-methylcarbamates [ArN(CH3)CO2CH3] as intermediates. The reaction is an example of a synthesis with low environmental impact: it couples the use of a non-toxic methylating agent (DMC, in place of the highly toxic methyl halides or dimethyl sulfate) with eco-friendly catalysts (zeolites) in a waste-free process.

Examples of amphitropic polymers: monolayer film, Langmuir–Blodgett film and liquid-crystalline properties of some polymeric amphiphiles containing cholestanol moieties and those of some closely related non-polymeric amphiphiles

A range of alternating copolymers were prepared by free-radical-initiated copolymerizations of maleic anhydride with a series of α-alkenes containing cholestanyl moieties. Derivatives of these copolymers were prepared by reacting the anhydride residues with methanol, water, dimethylamine and/or morpholine. A related series of non-polymeric amphiphiles containing steroid moieties was also prepared. Isotherms were measured for monolayers of the various polymers and the various non-polymeric amphiphiles on water and, where possible, Langmuir–Blodgett (LB) multilayers were prepared. The majority of the materials gave good isotherms (relatively steep with collapse pressures >40 nM m–1) indicating that the monolayers were ordered and, as determined by the detection of Bragg peaks by X-ray diffraction, Y-type LB films with regular layer structures. Appropriate materials were also examined, by optical microscopy and differential scanning calorimetry (DSC), for possible liquid-crystalline properties. Four polymers and one non-polymeric amphiphile exhibited smectic A mesophases. Another non-polymeric amphiphile exhibited a cholesteric mesophase. Thus, examples were found of amphitropic polymers and non-polymeric amphiphiles which can form organised molecular arrangements both because they are amphiphilic and because they contain mesogens.

Improvement of antibody surface density by orientation of reduced fragments

Abstract A procedure for the orientation of antibody fragments at the gas-water interface is described and preliminary results are presented. The method exploits the presence of the reactive sulfhydryl group of a reduced antibody fragment which can react with a floating monolayer. Surface pressure measurements show a strong interaction between the reduced fragments and the monolayer. Deposited films are characterised by a fluorescent immunoassay and ellipsometry and the results indicate that the antibody fragments are oriented with a high packaging densitiy.