Francesca Ceccacci

Unravelling the structure of protic ionic liquids with theoretical and experimental methods: ethyl-, propyl- and butylammonium nitrate explored by Raman spectroscopy and DFT calculations.

We present an analysis of gas-phase structures of small clusters of n-alkylammonium nitrates (ethyl, propyl, and butyl) together with vibrational Raman spectroscopy of their respective liquid phases. The assignment and interpretation of the resonant frequencies have been performed by comparison with high-quality ab initio (DFT) computations. The theoretical spectra are in excellent agreement with the measured ones and allow the interpretation and assignment of almost all the spectral features. A careful analysis of the vibrational frequencies and of the electronic structure of the compounds has provided additional information on various structural features and on the rather complex hydrogen bonding network that exists in such compounds. A geometric structure of the short-range local arrangement in the bulk phases is also proposed.

Determination of the rotational barrier of a chiral biphenyl: Comparison of theoretical and experimental data

Abstract The rotational barrier of chiral 2-carboxy-2′-methoxy-6-nitrobiphenyl has been evaluated both by density functional calculations, at the B3LYP/6-31G(d) and B3LYP/6-311+G(d,p) levels of theory, and by HF and post HF MP2 calculations at the 6-31G(d) level of theory. The DFT computed data, which seemed almost independent of the basis set used, are in good agreement with the values obtained from dynamic HPLC enantiomerization experiments and from the racemization rate constant of one of the enantiomers obtained by CD. The HF model seems to overestimate the barrier whereas the MP2 calculations confirm the DFT results.

Conformational isomerisms and nano-aggregation in substituted alkylammonium nitrates ionic liquids: An x-ray and computational study of 2-methoxyethylammonium nitrate

In this study, we discuss, using molecular dynamics simulations and energy-dispersive x-ray diffraction data, how a conformational isomerism can dramatically alter the nanosegregation phenomena that take place in a prototypical ionic liquid. The diffraction patterns of liquid 2-methoxyethylammonium nitrate are compared with the results from molecular dynamics simulations. The simulations conditions and force field parameters have been varied producing different charge models and different populations of conformers of the cation. We show that, while the short range structure is relatively unchanged in the models, the long range aggregation phenomena deemed responsible for the appearance of low Q peaks in the X-ray patterns strongly depend on the choice of the charge model. In the title compound, the best agreement with the experiment, where no low Q peaks appear, occurs if the point charges are calculated using the gauche conformation of the cation, which is characterized by an intramolecular hydrogen bond between ammonium and ether groups.

Structural characterization of zinc(II) chloride in aqueous solution and in the protic ionic liquid ethyl ammonium nitrate by x-ray absorption spectroscopy

Extended x-ray absorption fine structure (EXAFS) spectroscopy has been used to investigate the species and structures existing in a series of ZnCl(2)-H(2)O-NaCl solutions with different chloride/zinc ratios and in a solution of ZnCl(2) in the protic ionic liquid ethyl ammonium nitrate (EAN). The average coordination numbers and distances of zinc species were determined from the analysis of the EXAFS data. In aqueous solution the number of chloride ions tightly bounded to Zn(2+) is significantly related to the chloride/zinc ratio, and no inner complex formation between Zn(2+) and Cl(-) ions has been detected for low ZnCl(2) concentration (0.1 and 0.2 M). Conversely, in the same concentration range (0.13 M) the ZnCl(2) species do not dissociate in EAN and the Zn(2+) first coordination shell has two chloride ions and is completed by two oxygen atoms of the nitrate anion. The results of this investigation show that notwithstanding the existence of similar characteristics between EAN and water, the solvation properties of the two solvents are markedly different.

Deracemization of bilirubin as the marker of the chirality of micellar aggregates.

The deracemization of bilirubin in micellar aggregates of structurally correlated chiral surfactants was studied by circular dichroism experiments and exploited as the marker of the expression of chirality of the aggregates. The obtained results suggest that the hydrophobic interactions control the transfer of chirality from the monomers to the aggregates, and that different regions of the same aggregate might feature opposite enantiorecognition capabilities.

Novel locally active estrogens accelerate cutaneous wound healing. A preliminary study.

New 17beta-estradiol (E2) derivatives 1-11 were synthesized from an estrone derivative by addition of organometallic reagents prepared from protected alpha,omega-alkynols and further elaboration of the addition products. The estrogenic activity of these novel compounds was determined using in vitro binding competition assay and transactivation analysis. Among the E2 derivatives synthesized, compound 2 showed the highest transactivation potency and was therefore tested for its ability to modulate cutaneous wound healing in vivo. Compound 2s ability to accelerate wound healing in ovariectomized mice and decrease the production of inflammatory molecules was comparable to that of E2. However, the activity of compound 2 was not superimposable to E2 with regard to the cells involved in the wound repairing process. When locally administered, compound 2 did not show any systemic activity on ER. This class of compounds with clear beneficial effects on wound healing and suitable for topical administration may lead to the generation of innovative drugs for an area of unmet clinical need.

Discrimination of the enantiomers of new biphenylic derivatives in chiral micellar aggregates

The synthesis and characterization of two new chiral biphenylic derivatives is reported. The rotational barriers have been calculated on simpler homologues. The racemic mixtures of the two compounds have been used as probes of chirality for exploring the sites of chiral recognition in chiral micellar aggregates. Results suggest that one of the sites of chiral discrimination is the hydrophobic part of the aggregates, far from the stereogenic centres.

Diastereoselective Total Synthesis of (+)-13-Stemarene by Fourth Generation Methods: A Formal Total Synthesis of (+)-18-Deoxystemarin

The problem of constructing diastereoselectively the C/D ring system of stemarane diterpenes from a bicyclo[2.2.2]octane intermediate was solved resulting in very simple synthesis of (+)-13-stemarene 1. The obtaining of the latter represents also a formal synthesis of (+)-18-deoxystemarin 2. In the key step, the epimeric mixture 10, dissolved in toluene, was converted by the action of TsOH into (+)-stemar-13-en-15-one 28.

Regio- and diastereoselective synthesis and X-ray structure determination of (+)-2-deoxyoryzalexin S from (+)-podocarpic acid. Structural nonidentity with its nominal natural isolated enantiomer

(+)-2-Deoxyoryzalexin S (1), the nominal enantiomer of a diterpenoid isolated in Chile from Calceolaria species, was regio- and diastereoselectively synthesized from (+)-podocarpic acid. (+)-2-Deoxyoryzalexin S (1) was characterized also as its acetyl derivative, (+)-2, whose structure was confirmed by X-ray crystallographic analysis. Surprisingly, comparison of the data recorded for (+)-1 and (+)-2 and those reported in the literature for the Calceolaria isolated diterpenoid 1 and its derivative (-)-2 showed some differences, suggesting that the latter do not possess the proposed structures.

Inclusion of new 5-fluorouracil amphiphilic derivatives in liposome formulation for cancer treatment

Correction for ‘Inclusion of new 5-fluorouracil amphiphilic derivatives in liposome formulation for cancer treatment’ by M. Petaccia et al., Med. Chem. Commun., 2015, 6, 1639–1642.