Mass spectrometric characterization of substituted 2-thiazolin-4-one derivatives

Electron ionization mass spectrometry was used for the structural characterization of substituted 2-thiazolin-4-one derivatives in the gas phase. The compounds follow common fragmentation pathways, producing ions whose abundances are dependent on the chemical nature of the substituent at position 2. Collision-induced dissociation tandem mass spectrometric experiments, carried out on both molecular ions and fragment ions produced in the source, allowed the elucidation of gas-phase decompositions. The presence of tautomeric forms is suggested for some ionic species. Rapid identification of a primary or secondary amine moiety at position 2 of the thiazoline ring can be achieved by the detection of characteristic fragmentations occurring both in the ion source and under the collision-induced dissociation regime.     

On the mechanism of the thermal retrocycloaddition of pyrrolidinofullerenes (retro-Prato reaction)

In contrast to N-methyl or N-unsubstituted pyrrolidinofullerenes, which efficiently undergo the retrocycloaddition reaction to quantitatively afford pristine fullerene, N-benzoyl derivatives do not give this reaction under the same experimental conditions. To unravel the mechanism of the retrocycloaddition process, trapping experiments of the in-situ thermally generated azomethine ylides, with an efficient dipolarophile were conducted. These experiments afforded the respective cycloadducts as an endo/exo isomeric mixture. Theoretical calculations carried out at the DFT level and by using the two-layered ONIOM (our own n-layered integrated molecular orbital and molecular mechanics) approach underpin the experimental findings and predict that the presence of the dienophile is not a basic requirement for the azomethine ylide to be able to leave the fullerene surface under thermal conditions. Once the 1,3-dipole is generated in the reaction medium, it is efficiently trapped by the dipolarophile (maleic anhydride or N-phenylmaleimide). However, for N-unsubstituted pyrrolidinofullerenes, the participation of the dipolarophile in assisting the 1,3-dipole to leave the fullerene surface throughout the whole reaction pathway is also a plausible mechanism that cannot be ruled out.     

Cardanol as a replacement for cholesterol into the lipid bilayer of POPC liposomes

Large unilamellar liposomes were prepared by hydration of 1-palmitoyl-2-oleylphosphatydilcholine (POPC) films and subsequent extrusion of the obtained liposomal suspension. Inclusion of cholesterol and cardanol brings about a stabilization of the membranes of the liposomes, as determined by their rates of release of entrapped 5(6)-carboxyfluorescein. The liposome breakdown was promoted by a non-ionic surfactant (Triton X-100) and the kinetic measurements were carried out by fluorimetry in water at 25 degrees C. Morphological analyses of giant POPC liposomes in the presence and in the absence of both guests were also performed. The results obtained suggest the use of cardanol (an easy available natural product) as a replacement for cholesterol as a new possibility for stabilizing liposomes in drug targetting.     

Efficient synthesis and environmentally friendly reactions of PEG-supported 1,2-diaza-1,3-butadiene

[reaction: see text] Here, we report the protocol for the preparation of new poly(ethylene glycol)-supported 1,2-diaza-1,3-butadiene. In addition, we discuss an application of this supported reagent in an efficient and environmentally friendly one-pot synthesis of 2-thiazol-4-one derivatives by reaction with thioamides.     

Straightforward entry into 5-hydroxy-1-aminopyrrolines and the corresponding pyrroles from 1,2-diaza-1,3-butadienes

The synthesis of 5-hydroxy-1-aminopyrroline-3-carboxylic acid derivatives and 5-unsubstituted-1-aminopyrrole-3-carboxylic acid derivatives from 1,2-diaza-1,3-butadienes and aldehydes is presented. These domino reactions offer the advantage of executing multistep transformation without intermediate workup procedures. The stereoselectivity of ring closure to 5-hydroxy-1-aminopyrroline-3-carboxylic acid derivatives and phenyl transposition to 2,3-diphenyl-1-aminopyrrole-3-carboxylic acid derivatives are also studied.     

From targeted aza-Michael addition to linked azaheterocyclic scaffolds

A straightforward method for the synthesis of spaced, phenyl-linked bis(thiohydantoin) derivatives and (thio)hydantoins spiro-fused to pyrroline ring has been developed. All the synthetic strategies here presented rely on initial aza-Michael addition followed by acylation/regioselective ring-closure step involving DD, primary amine and iso(thio)cyanate in a 3-CR providing 1,3,5-trisubstituted (thio)hydantoins. The choice of opportune acyclic reagents in the sequential 3-CR followed by 1,4-nucleophilic addition/intramolecular ring closing and 1,3-dipolar cycloaddition permits a number of C–N and C–C formation that realizes different kind of linkage between several pharmacophores.