Synthesis and Evaluation of 2'-Deoxy-2'-Spirodiflurocyclopropyl Nucleoside Analogs.

The preparation of 2'-deoxy-2'-siprodifluorocyclopropany-lnucleoside analogs has been achieved from α-d-glucose in several steps. The key step in the synthesis was the introduction of the difluorocyclopropane through a difluorocarbene type reaction at the 2'-position. Then, a series of novel 2'-deoxy-2'-spirodifluorocyclopropanyl nucleoside analogs were synthesized using the Vorbrüggen method. All the synthesized nucleosides were characterized and subsequently evaluated against hepatitis C and influenza A virus strains in vitro.

Shelf-stable electrophilic reagents for trifluoromethylthiolation.

Fluorine, which is the most electronegative element and has a small atomic radius, plays a key role in pharmaceutical, agrochemical, and materials sciences. One of the fluoroalkyl groups, the trifluoromethylthio group (CF3S-), has been well-recognized as an important structural motif in the design of lead compounds for new drug discovery because of its high lipophilicity (Hansch lipophilicity parameter π = 1.44) and strong electron-withdrawing properties, which could improve the drug molecule's cell-membrane permeability and enhance its chemical and metabolic stability. While classic methods for the preparation of trifluoromethylthiolated compounds typically involve halogen-fluorine exchange reactions of polyhalogenomethyl thioethers or trifluoromethylation of sulfur-containing compounds under harsh reaction conditions, an alternative but more attractive strategy is direct trifluoromethylthiolation of the substrate at a late stage by employing an electrophilic trifluoromethylthiolating reagent. Although several electrophilic trifluoromethylthiolating reagents have been reported previously, these reagents either require a strong Lewis acid/Brønsted acid as an activator or suffer from a toxic nature or limited substrate scope. To address these problems, in late 2011 we initiated a project with the aim to develop new, shelf-stable, and highly reactive electrophilic trifluoromethylthiolating reagents that could easily install the trifluoromethylthio group at the desired positions of the drug molecule at a late stage of drug development. Inspired by the broad reactivity of the hypervalent iodine reagent, we initially discovered a highly reactive trifluoromethylthiolating reagent, trifluoromethanesulfenate 1a. Structure-reactivity studies disclosed that the iodine atom of reagent 1a does not play an important role in this reagent's reactivity. Consequently, a simplified second-generation electrophilic reagent, trifluoromethanesulfenate 1b, was developed. In parallel, we developed another shelf-stable, highly reactive electrophilic reagent with a broad substrate scope, N-trifluoromethylthiosaccharin (2). In this Account, we mainly describe our discovery of these two different types of electrophilic trifluoromethylthiolating reagents, trifluoromethanesulfenates 1a and 1b and N-trifluoromethylthiosaccharin 2. Systematic studies showed that both types of reagents are highly reactive toward a wide range of nucleophiles, yet the substrate scopes of these two different types of reagents are complementary. In particular, reagents 1a and 1b are more reliable in transition-metal-catalyzed reactions such as copper-catalyzed trifluoromethylthiolation of aryl/vinyl/alkylboronic acids and silver-catalyzed decarboxylative trifluoromethylthiolation of aliphatic carboxylic acids as well as in the organocatalytic asymmetric trifluoromethylthiolation of ß-keto esters and oxindoles. Reagent 2 is more electrophilic than reagents 1a and 1b and is more efficient for direct trifluoromethylthiolation with nucleophiles such as alcohols, amines, thiols, and electron-rich arenes. The ease in preparation, broad scope, and mild reaction conditions make reagents 1a, 1b, and 2 very attractive as general reagents that allow rapid installation of the trifluoromethylthio group into small molecules.

Complementary regioselectivity in Rh(III)-catalyzed insertions of potassium vinyltrifluoroborate via C-H activation: preparation and use of 4-trifluoroboratotetrahydroisoquinolones.

Potassium vinyltrifluoroborate was found to be an efficient partner with benzamide derivatives for Rh(III)-catalyzed annulations. 4-Trifluoroboratotetrahydroisoquinolones were generated under mild conditions, affording a regioisomerically complementary substitution pattern to other alkenes in related reactions. These new boron-containing building blocks were derivatized by N-arylations, retaining the boron substituent for further elaboration.

A novel fluorinated stilbene exerts hepatoprotective properties in CCl(4)-induced acute liver damage.

There has been a recently increase in the development of novel stilbene-based compounds with in vitro anti-inflamatory properties. For this study, we synthesized and evaluated the anti-inflammatory properties of 2 fluorinated stilbenes on carbon tetrachloride (CCl4)-induced acute liver damage. To achieve this, CCl4 (4 g·kg(-1), per os) was administered to male Wistar rats, followed by either 2-fluoro-4'-methoxystilbene (FME) or 2,3-difluoro-4'-methoxystilbene (DFME) (10 mg·kg(-1), per os). We found that although both of the latter compounds prevented cholestatic damage (γ-glutamyl transpeptidase activity), only DFME showed partial but consistent results in the prevention of necrosis, as assessed by both alanine aminotransferase activity and histological analysis. Since inflammatory responses are mediated by cytokines, mainly tumour necrosis factor α (TNF-α), we used the Western blot technique to determine the action of FME and DFME on the expression level of this cytokine. The observed increase in the level of TNF-α caused by CCl4 administration was only prevented by treatment with DFME, in agreement with our biochemical findings. This result was confirmed by measuring interleukin-6 (IL-6) levels, since the expression of this protein depends on the level of TNF-α. In this case, DFME completely blocked the CCl4-induced increase of IL-6. Our results suggest that DFME possesses greater anti-inflammatory properties in vivo than FME. DFME constitutes a possible therapeutic agent for liver disease and could serve as a template for structure optimization.

Potent and selective 5-LO inhibitor bearing benzothiophene pharmacophore: discovery of MK-5286.

The strategy and SAR studies that led to the discovery of a novel potent and orally available 5-lipoxygenase (5-LO) inhibitor 3-(4-fluorophenyl)-6-({4-[(1S)-1-hydroxy-1-(trifluoromethyl)propyl]-1H-1,2,3-triazol-1-yl}methyl)-1-benzothiophene-2-carboxamide ((S)-2l or MK-5286) were described.

Clubbed [1,2,3] triazoles by fluorine benzimidazole: a novel approach to H37Rv inhibitors as a potential treatment for tuberculosis.

A Novel Clubbed [1,2,3] triazoles with fluorine benzimidazole series of H37Rv strain inhibitors, potentially useful for the treatment of tuberculosis is disclosed on the basis of promising results of preliminary antimicrobial study. Evaluation of the SAR of substitution within these series has followed the identification of a range of compounds. Some of the derivatives are under further evaluation showing better considerable activity compared to rifampin.

New fluoro-diphenylchalcogen derivatives to explore the serotonin transporter by PET.

A series of fluorinated diphenylchalcogen derivatives, possessing a sulfur or an oxygen bridge, has been prepared with the aim to get a suitable radiotracer to image the SERT in vivo using positron emission tomography (PET). The compounds were synthesized and assayed toward the serotonin (SERT), dopamine (DAT), and norepinephrine (NET) transporters. Among the developed series, five compounds display a high SERT affinity (K(i): 0.27-2.91 nM range) and can be labeled either with carbon-11 or fluorine-18.

Incorporation of trifluoroisoleucine into proteins in vivo.

Two fluorinated derivatives of isoleucine: d,l-2-amino-3-trifluoromethyl pentanoic acid (3TFI, 2) and d,l-2-amino-5,5,5-trifluoro-3-methyl pentanoic acid (5TFI, 3) were prepared. 5TFI was incorporated into a model target protein, murine dihydrofolate reductase (mDHFR), in an isoleucine auxotrophic Escherichia coli host strain suspended in 5TFI-supplemented minimal medium depleted of isoleucine. Incorporation of 5TFI was confirmed by tryptic peptide analysis and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) of the protein product. Amino acid analysis showed that more than 93% of the encoded isoleucine residues were replaced by 5TFI. Measurement of the rate of activation of 5TFI by the E. coli isoleucyl-tRNA synthetase (IleRS) yielded a specificity constant (k(cat)/K(m)) 134-fold lower than that for isoleucine. 5TFI was successfully introduced into the cytokine murine interleukin-2 (mIL-2) at the encoded isoleucine positions. The concentration of fluorinated protein that elicits 50% of the maximal proliferative response is 3.87 ng/mL, about 30% higher than that of wild-type mIL-2 (EC(50) = 2.70 ng/mL). The maximal responses are equivalent for the fluorinated and wild-type cytokines, indicating that fluorinated proteins can fold into stable and functional structures. 3TFI yielded no evidence for in vivo incorporation into recombinant proteins, and no evidence for activation by IleRS in vitro.