A novel general method for preparation of α-fluoro-α-arylcarboxylic acid. Direct fluorination of silyl ketene acetals with Selectfluor®

The Enediolate Chemistry of Free Carboxylic Acids

The synthetic methodologies for the α-functionalization of free carboxylic acids through the enediolate intermediates are summarized in this review. In general, the enediolates could be generated in situ or transiently from free carboxylic acids with a stoichiometric or catalytic amount of protection reagents, including metal, boron, and silicon reagents. The in situ or transient generated enediolates were subsequently subjected to racemic or asymmetric reactions with various electrophiles, producing the α-functionalized free carboxylic acids in a single step. In addition, the enediolate could undergo an α-oxidation reaction with TEMPO through the radical process.

Benzylic Fluorination Induced by a Charge-Transfer Complex with a Solvent-Dependent Selectivity Switch

We present a divergent strategy for the fluorination of phenylacetic acid derivatives that is induced by a charge-transfer complex between Selectfluor and 4-(dimethylamino)pyridine. A comprehensive investigation of the conditions revealed a critical role of the solvent on the reaction outcome. In the presence of water, decarboxylative fluorination through a single-electron oxidation is dominant. Non-aqueous conditions result in the clean formation of α-fluoro-α-arylcarboxylic acids.

Boron-Catalyzed alfa-C-H Fluorination of Aryl Acetic Acids

The catalytic alfa-C-H fluorination of aryl acetic acid was achieved with good functional tolerance in the presence of a boron catalyst. A series of alfa-fluoro aryl acetic acids was obtained...

Nickel-Catalyzed Cross-Coupling of Ethyl Chlorofluoroacetate with Aryl Bromides

A combinatorial nickel-catalyzed monofluoroalkylation of aryl bromides with the industrial raw regent ethyl chlorofluoroacetate has been developed. The two key factors to successful conversion are the combination of nickel with readily available nitrogen and phosphine ligands and the using of a mixture of different solvents. Mechanistic investigations indicated a new zinc regent might generated in situ and be involved in the reaction process.

Visible light-induced monofluoromethylenation of heteroarenes with ethyl bromofluoroacetate

A mild approach for the direct introduction of an ethoxycarbonylmonofluoromethyl group into heteroarenes via visible light photocatalysis has been developed.

Syntheses of fluorooxindole and 2-fluoro-2-arylacetic acid derivatives from diethyl 2-fluoromalonate ester

Diethyl 2-fluoromalonate ester is utilised as a building block for the synthesis of 2-fluoro-2-arylacetic acid and fluorooxindole derivatives by a strategy involving nucleophilic aromatic substitution reactions with ortho-fluoronitrobenzene substrates followed by decarboxylation, esterification and reductive cyclisation processes.

Semisynthetic ursolic acid fluorolactone derivatives inhibit growth with induction of p21(waf1) and induce apoptosis with upregulation of NOXA and downregulation of c-FLIP in cancer cells

A series of ursolic acid ((1S,2R,4aS,6aR,6aS,6bR,8aR,10S,12aR,14bS)-10-hydroxy-1,2,6a,6b,9,9,12a-heptamethyl-2,3,4,5,6,6a,7,8,8a,10,11,12,13,14b-tetradecahydro-1H-picene-4a-carboxylic acid) derivatives with a 12-fluoro-13,28β-lactone moiety were synthesized using the electrophilic fluorination reagent Selectfluor. The antiproliferative effects of these novel compounds were evaluated in AsPC-1 pancreatic cancer cells, and the structure-activity relationships (SARs) were evaluated. Of the compounds synthesized, ursolic acid derivatives carrying a heterocyclic ring, such as imidazole or methylimidazole, and cyanoenones were among the more potent inhibitors of AsPC-1 pancreatic cancer cell growth. 2-Cyano-3-oxo-12α-fluoro-urs-1-en-13,28β-olide, compound 20, was the most effective inhibitor with IC(50) values of 0.7, 0.9 and 1.8 μM in pancreatic cancer cell lines AsPC-1, MIA PaCa-2 and PANC-1, respectively. This compound also exhibited better antiproliferative activities against breast (MCF7), prostate (PC-3), hepatocellular (Hep G2) and lung (A549) cancer cell lines, with IC(50) values lower than 1 μM. The mechanism of action by which these compounds exert their biological effect was evaluated in AsPC-1 cells using the most potent inhibitor synthesized, compound 20. At 1 μM, the cell cycle arrested at the G1 phase with upregulation of p21(waf1). Apoptosis was induced at an inhibitor concentration of 8 μM with upregulation of NOXA and downregulation of c-FLIP. These data indicate that fluorolactone derivatives of ursolic acid have improved antiproliferative activity, acting through arrest of the cell cycle and induction of apoptosis.

Inhibition of amyloidogenesis by nonsteroidal anti-inflammatory drugs and their hybrid nitrates

Poor blood-brain barrier penetration of nonsteroidal anti-inflammatory drugs (NSAIDs) has been blamed for the failure of the selective amyloid lowering agent (SALA) R-flurbiprofen in phase 3 clinical trials for Alzheimer's disease (AD). NO-donor NSAIDs (NO-NSAIDs) provide an alternative, gastric-sparing approach to NSAID SALAs, which may improve bioavailability. NSAID analogues were studied for anti-inflammatory activity and for SALA activity in N2a neuronal cells transfected with human amyloid precursor protein (APP). Flurbiprofen (1) analogues were obtained with enhanced anti-inflammatory and antiamyloidogenic properties compared to 1, however, esterification led to elevated Aβ(1-42) levels. Hybrid nitrate prodrugs possessed superior anti-inflammatory activity and reduced toxicity relative to the parent NSAIDs, including clinical candidate CHF5074. Although hybrid nitrates elevated Aβ(1-42) at higher concentration, SALA activity was observed at low concentrations (≤1 μM): both Aβ(1-42) and the ratio of Aβ(1-42)/Aβ(1-40) were lowered. This biphasic SALA activity was attributed to the intact nitrate drug. For several compounds, the selective modulation of amyloidogenesis was tested using an immunoprecipitation MALDI-TOF approach. These data support the development of NO-NSAIDs as an alternative approach toward a clinically useful SALA.