Fluorinated Triazole Foldamers: Folded or Extended Conformational Preferences

The Ministère de l'Enseignement Supérieur et de la Recherche (MESR) is thanked for financial support for José Laxio Arenas. The China Scholarship Council is thanked for financial support for Yaochun Xu. The authors thank Pr. Vadim Soloshonok and TOSOH F-TECH, Inc. for the kind gift of N-terbutyl-sulfinylimine.

Direct Access to Substituted 4-CF3 β-Lactams at the C-3 Position

Mono- and disubstituted 4-CF₃ β-lactams at the C-3 position have been obtained stereoselectively under basic conditions. A wide range of function such as alcohols, alkyls, aryls, esters, and double and triple bonds have been introduced.

Direct Amination of Arenes with Azodicarboxylates Catalyzed by Bisulfate Salt/HFIP Association

A mild and efficient amination of arenes with azodicarboxylates using potassium bisulfate (KHSO4) as the catalyst in 1,1,1,3,3,3-hexafluoro-2-propanol has been developed. This protocol allowed the amination of a broad range of arenes leading to corresponding hydrazides in good to excellent yields.

Bisulfate Salt-Catalyzed Friedel-Crafts Benzylation of Arenes with Benzylic Alcohols

We report here a method of direct Friedel-Crafts benzylation of arenes with benzylic alcohols using cheap and readily available bisulfate salt as the catalyst in hexafluoroisopropanol. The catalytic system is powerful with a quite diverse group of functionalized arenes and benzylic alcohols. These mild conditions provide a straightforward synthesis of a variety of unsymmetrical diarylmethanes in high yield with good to high regioselectivity. An S_N1 mechanism involving activation of the hydroxy group through a hydrogen bond is proposed.

Towards a general synthesis of di-aza-amino acids containing peptides

Three synthetic routes are studied and compared to introduce two consecutive aza-amino acids bearing various side chains into peptides.

Friedel–Crafts alkylation reaction with fluorinated alcohols as hydrogen-bond donors and solvents

An effective and clean FC alkylation of indoles and electron-rich arenes with β-nitroalkenes in HFIP was reported. The desired products are formed rapidly in excellent yields under mild conditions without the need for any additional catalysts or reagents. Further, this methodology can be applied to one-pot synthesis of biologically active tryptamine derivatives.

Friedel–Craft alkylation of heterocycle derivatives with β-nitroalkenes was performed in HFIP. The one-pot synthesis of tryptamines could be applied.

N-Difluoromethyl-triazole as a constrained scaffold in peptidomimetics

The N-difluoromethyl triazolo-β-aza-ε-amino acid present in the core of peptides led to constrained conformations due to CH–F and NH–F interactions.

Designed Glycopeptidomimetics Disrupt Protein-Protein Interactions Mediating Amyloid β-Peptide Aggregation and Restore Neuroblastoma Cell Viability

How anti-Alzheimer's drug candidates that reduce amyloid 1-42 peptide fibrillization interact with the most neurotoxic species is far from being understood. We report herein the capacity of sugar-based peptidomimetics to inhibit both Aβ1-42 early oligomerization and fibrillization. A wide range of bio- and physicochemical techniques, such as a new capillary electrophoresis method, nuclear magnetic resonance, and surface plasmon resonance, were used to identify how these new molecules can delay the aggregation of Aβ1-42. We demonstrate that these molecules interact with soluble oligomers in order to maintain the presence of nontoxic monomers and to prevent fibrillization. These compounds totally suppress the toxicity of Aβ1-42 toward SH-SY5Y neuroblastoma cells, even at substoichiometric concentrations. Furthermore, demonstration that the best molecule combines hydrophobic moieties, hydrogen bond donors and acceptors, ammonium groups, and a hydrophilic β-sheet breaker element provides valuable insight for the future structure-based design of inhibitors of Aβ1-42 aggregation.

(19)F NMR monitoring of the eukaryotic 20S proteasome chymotrypsin-like activity: an investigative tool for studying allosteric regulation

The proteasome displays three distinct proteolytic activities. Currently, proteasome inhibitors are evaluated using specific fluorescent substrates for each of the individual active sites. However, the photophysical properties of the commonly used fluorophores are similar and thus, the simultaneous monitoring of the three proteolytic activities is not possible. We have developed a bimodal fluorescent fluorinated substrate as a novel tool to study the chymotrypsin-like (ChT-L) proteolytic activity and its regulation by inhibitors and by substrates of trypsin-like (T-L) and caspase-like sites (PA). We demonstrate that this substrate is reliable to evaluate the ChT-L inhibitory activity of new molecules either by fluorescence or (19)F NMR spectroscopy. We have found that the ChT-L activity is dramatically reduced in the presence of T-L and PA substrates. This work provides a proof of concept that the fluorinated substrate enables investigation of the allosteric regulation of the ChT-L activity.

Reactivity of carbon dioxide in hydrofluoroethers: a facile access to cyclic carbonates

The reactivity of CO₂ dissolved in high quantities in hydrofluoroethers was enhanced and allowed the formation of cyclic carbonates from epoxides with excellent selectivities.

A one-pot synthesis of 3-trifluoromethyl-2-isoxazolines from trifluoromethyl aldoxime

Functionalized 3-trifluoromethyl-2-isoxazolines and 3-trifluoromethylisoxazoles were easily prepared from trifluoromethyl aldoxime 2 under mild conditions by using DIB as oxidant. Theoretical studies of the reactivity of trifluoroacetonitrile oxide 4 toward olefins and alkynes were carried out. The 3-trifluoromethyl-2-isoxazolines were ring-opened with NaBH4 and NiCl2 to yield the corresponding trifluoromethylated γ-amino alcohols.

Carbonylhydrazide-based molecular tongs inhibit wild-type and mutated HIV-1 protease dimerization

We have designed and synthesized new molecular tongs based on a rigid naphthalene scaffold and evaluated their antidimer activity on HIV-1 protease (PR). We inserted carbonylhydrazide and oligohydrazide (azatide) fragments into their peptidomimetic arms to reduce hydrophobicity and increase metabolic stability. These fragments are designed to disrupt the protein-protein interactions by reproducing the hydrogen bond pattern found in the antiparallel β-sheet formed between the N- and C-ends of the two monomers in the native PR. Kinetic analyses and fluorescent probe binding studies showed that several molecular tongs can inhibit PR dimerization. The best nonpeptidic molecular tongs to date were obtained with an inhibition constant K(id) of 50 nM for PR and 80 nM for the multimutated protease ANAM-11. The PR inhibition was selective, the aspartic proteases renin and pepsin were not inhibited.

Abstract 1925: Trifluoromethylated artemisinin dimers demonstrate a potent anti-cancer activity in vitro and in vivo

Beside their widely recognised efficacy as antimalaric drugs, artemisinin derivatives are also known for their cytotoxic properties since the early nineties. More recently, artemisinin dimers (ADs) were shown to possess an increased potential as anti-cancer agents due to their ability to inhibit cancer cells proliferation in the low nanomolar range. Taking advantage of an original chemistry, we synthesized a new series of trifluoromethylated artemisnin dimers which proved to be particularly potent depending on the size and nature of the linker. Different mode of linkage were performed by either carbon 16 or carbon 10 and were tested in vitro and in vivo. Best combination was found in a hybrid linking position delivering non-symmetrical C10-C16 ADs. One of the lead compound of this series, F98458 demonstrated a moderate (but statiscally significative) anti-tumor activity in mice against a human melanoma xenograft that is, to our knowledge, the first demonstration of in vivo antitumor properties of ADs in preclinical models. Many efforts to understand the molecular origin of the cytotoxic effect of monomeric artemisinin derivatives have been undertaken. One of the aims of this study was to investigate the mechanism of action of ADs in comparison with artemisinin: the antimalaric drug artesunate, a representative monomeric derivative of artemisinin, is known to induce DNA damage and ROS generation while our ADs did not under the same experimental conditions. Moreover ADs did not induce apoptosis (caspase 3/7, annexin V), leading us to investigate cell death related to senescence and autophagy. We have also synthesized partially reduced ADs possessing only one endoperoxide functionality. These compounds did show the same potency than non reduced ADs, underlaying that a tight molecular recognition is involved in its biological response. All these observations suggest that monomeric artemisinin derivatives such as artesunate and ADs possess distinct modes of action. The high in vitro potency associated with the in vivo response led us to synthesize affinity probes in order to identify the molecular target of ADs which could provide fundamental informations for further developpement of these compounds as anti-cancer agents. This work currently underway will also be discussed.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1925. doi:1538-7445.AM2012-1925

The fluorous effect in biomolecular applications

From being a niche area only a few decades ago, fluorous chemistry has gained momentum and is, nowadays, a fervent area of research. It has brought forth, in fact, numerous applicative innovations that stretch among different fields: from catalysis to separation science, from supramolecular to materials and analytical chemistry. Recently, the unique features of perfluorinated compounds have reached the attention of the biochemists' audience. This tutorial review introduces the basic concepts of fluorous chemistry and illustrates its main biomolecular applications. Special attention has been given to fluorous microarrays and their combination with Mass-Spectroscopy (MS) techniques, to protein properties modification by the introduction of local fluorous domains, and to the most recent applications of (19)F-Magnetic Resonance Imaging ((19)F-MRI).

Solvent-promoted and -controlled aza-Michael reaction with aromatic amines

1,4-Addition of anilines onto Michael acceptors proceeds easily in specific polar protic solvents, without any promoting agent. According to the solvent and to the electrophile, the selectivity of the reaction can be finely tuned. With methyl acrylate as electrophile, only monoaddition takes place in water, while the diadduct is yielded in hexafluoroisopropyl alcohol (HFIP). The use of methyl vinyl ketone as a partner affords the monoadduct in water, the diadduct in trifluoroethanol (TFE), and the quinoline in HFIP.

Synthesis and cytotoxic activity of fluorinated analogues of Goniothalamus lactones. Impact of fluorine on oxidative processes

Novel fluorinated analogues of goniothalamin 1 and howiinol A 2 have been prepared from trifluorocrotonate derivatives. Trifluoromethyl goniothalamin (R/S) 4 showed a slightly lower activity than 1, while the trifluoromethyl howiinol A 16 exhibited similar activities on several cell lines in the micromolar range. Unlike (R) goniothalamin and howiinol A, trifluoromethyl parent compounds remained unchanged when submitted to biomimetic oxidative systems.

Synthesis of new triazole-based trifluoromethyl scaffolds

Trifluoromethyl propargylamines react with various azide derivatives to afford 1,4-disubstituted 1,2,3-triazoles through a Huisgen 1,3-dipolar cycloaddition. The reaction is catalyzed by a Cu(I) species in acetonitrile, and the corresponding products are obtained in good yields. This process thus offers an entry to new trifluoromethyl peptidomimetics as interesting scaffolds.