Clelia Giannini

A convenient procedure for the synthesis of tetrathia-[7]-helicene and the selective α-functionalisation of terminal thiophene ring

This paper describes a convenient preparation of tetrathia-[7]-helicene (TH[7]), the generation of the α-anion on the terminal thiophene ring, and the synthesis of the 2-formyl-tetrathia-[7]-helicene (2-CHO-TH[7]). The key intermediate trans-1,2-dibenzodithiophene-ethene, prepared in 97% yield by McMurry coupling of the 2-formyl-benzo[1,2-b;4,3-b′]dithiophene, was transformed into TH[7] using a known procedure. The described method affords TH[7] in 46% overall yield, which is more than four times the yield previously reported in the literature. The α-anion of TH[7], which is easily generated on the α-position of one of the terminal thiophene rings, reacts with electrophilic reagents such as D2O and DMF. The latter reaction proved to be the best way to prepare 2-CHO-TH[7], a key intermediate for the preparation of new substituted heterohelicenes.

Dysidotronic acid, a new and selective human phospholipase A2 inhibitor from the sponge Dysidea sp.

Abstract A new bioactive sesquiterpenoid, named dysidotronic acid 1 , with a rearranged drimane skeleton has been isolated from the sponge Dysidea sp. from Vanuatu islands, along with bolinaquinone 2 . The chemical structure of 1 was determined on the basis of spectroscopic data. Dysidotronic acid significantly inhibited human synovial phospholipase A 2 (PLA 2 ) at 10 μM, with an IC 50 value of 2.6 μM and a higher selectivity and potency towards this enzyme than the reference inhibitor manoalide.

H-Aggregates Granting Crystallization-Induced Emissive Behavior and Ultralong Phosphorescence from a Pure Organic Molecule

Solid-state luminescent materials with long lifetimes are the subject of ever-growing interest from both a scientific and a technological point of view. However, when dealing with organic compounds, the achievement of highly efficient materials is limited by aggregation-caused quenching (ACQ) phenomena on one side and by ultrafast deactivation of the excited states on the other. Here, we report on a simple organic molecule, namely, cyclic triimidazole (C9H6N6), 1, showing crystallization-induced emissive (CIE) behavior and, in particular, ultralong phosphorescence due to strong coupling in H-aggregated molecules. Our experimental data reveal that luminescence lifetimes up to 1 s, which are several orders of magnitude longer than those of conventional organic fluorophores, can be realized under ambient conditions, thus expanding the class of organic materials for phosphorescence applications.

A new ‘one-pot’ synthesis of hydrazides by reduction of hydrazones

Abstract A new, high-yielding methodology for reducing hydrazones to hydrazines is described, which allows the synthesis of different mono-, di- and trisubstituted hydrazines. Moreover, the reduction step can be followed by an in situ reaction with a carboxylic acid making possible a ‘one-pot’ synthesis of trisubstituted hydrazides. The method is relatively general and, in principle, suitable for industrial applications.

The N‐terminus of mature human frataxin is intrinsically unfolded

Frataxin is a highly conserved nuclear‐encoded mitochondrial protein whose deficiency is the primary cause of Friedreich’s ataxia, an autosomal recessive neurodegenerative disease. The frataxin structure comprises a well‐characterized globular domain that is present in all species and is preceded in eukaryotes by a non‐conserved N‐terminal tail that contains the mitochondrial import signal. Little is known about the structure and dynamic properties of the N‐terminal tail. Here, we show that this region is flexible and intrinsically unfolded in human frataxin. It does not alter the iron‐binding or self‐aggregation properties of the globular domain. It is therefore very unlikely that this region could be important for the conserved functions of the protein.

Amphiasterins: a new family of cytotoxic metabolites from the marine sponge Plakortis quasiamphiaster

Abstract A new family of marine metabolites, named amphiasterins (1–17), was isolated from the marine sponge Plakortis quasiamphiaster. They can be divided in five structurally homogeneous groups, whose components differ only in the length and/or in the unsaturation degree of the alkyl side chain. The structures of these compounds were elucidated by spectroscopic data.

Synthesis of the first chiral PNA monomer labelled with a Fischer-type carbene complex

Abstract The synthesis, through a cross-metathesis reaction, of the first chiral peptide nucleic acid (PNA) monomer labelled with a Fischer-type carbene complex of chromium is reported. IR analysis of the new bioconjugate shows that the Cr(CO) 4 moiety represents a suitable spectroscopic probe for diagnostic purposes.

Isolation and structural elucidation of the crellastatins I-M: cytotoxic bis-steroid derivatives from the vanuatu marine sponge Crella sp

Abstract Continued investigation of cytotoxic extracts of the marine sponge Crella sp. has resulted in the discovery of crellastatins I-M (2–6). Their structures were determined by interpretation of their NMR spectroscopic and FABMS data. These new bis-steroid derivatives exhibited cytotoxic activity against NSCLC cell lines with IC50 values in the range of 1–8 μg/ml.

Cyclic Triimidazole Derivatives: Intriguing Examples of Multiple Emissions and Ultralong Phosphorescence at Room Temperature

The performance of solid luminogens depends on both their inherent electronic properties and their packing status. Intermolecular interactions have been exploited to achieve persistent room-temperature phosphorescence (RTP) from organic molecules. However, the design of organic materials with bright RTP and the rationalization of the role of interchromophoric electronic coupling remain challenging tasks. Cyclic triimidazole has been shown to be a promising scaffold for such purposes owing to its crystallization-induced room-temperature ultralong phosphorescence (RTUP), which has been associated with H-aggregation. Herein, we report three triimidazole derivatives as significant examples of multifaceted emission. In particular, dual fluorescence, RTUP, and phosphorescence from the molecular and supramolecular units were observed. H-aggregation is responsible for the red RTUP, and Br substituents favor yellow molecular phosphorescence while halogen-bonded Br⋅⋅⋅Br tetrameric units are involved in the blue-green phosphorescence.

Dysidotronic acid, a new sesquiterpenoid, inhibits cytokine production and the expression of nitric oxide synthase.

In a previous study, we reported a new bioactive sesquiterpenoid, named dysidotronic acid, to be a potent, selective human synovial phospholipase A(2) inhibitor. Dysidotronic acid is a novel, non-complex manoalide analogue lacking the pyranofuranone ring. We now investigate the effect of this compound on cytokine, nitric oxide and prostanoid generation on the mouse macrophage cell line RAW 264.7, where it showed a dose-dependent inhibition with inhibitory concentration 50% values in the micromolar range. This effect was also confirmed in the mouse air pouch injected with zymosan. Dysidotronic acid inhibited the production of tumor necrosis factor alpha and interleukin-1 beta as well as the production of nitric oxide, prostaglandin E(2) and leukotriene B(4). Decreased nitric oxide generation was the consequence of inhibition of the expression of nitric oxide synthase, whereas PGE(2) and LTB(4) reduction was due to inhibition of arachidonic acid bioavailability through a direct inhibitory effect of dysodotronic acid on secretory phospholipase A(2).