Negishi Coupling of Secondary Alkylzinc Halides with Aryl Bromides and Chlorides

An efficient palladium-catalyzed process has been developed for Negishi coupling of secondary alkylzinc halides with a wide range of aryl bromides and activated aryl chlorides. A palladium catalyst composed of a new biaryldialkylphosphine ligand, CPhos, effectively promotes the rate of the reductive elimination step relative to the rate of the undesired β-hydride elimination. The broad substrate scope and excellent ratio of the desired secondary to the undesired primary coupling product make this method a powerful and reliable tool for C(sp[superscript 3])−C(sp[superscript 2]) bond formation.National Institutes of Health (U.S.) (GM 46059)National Institutes of Health (U.S.) (GM 1S10RR13886-01

Anti-inflammatory nitro-fatty acids suppress tumor growth by triggering mitochondrial dysfunction and activation of the intrinsic apoptotic pathway in colorectal cancer cells

Nitro-fatty acids (NFAs) are endogenously occurring lipid mediators exerting strong anti-inflammatory effects and acting as anti-oxidants in a number of animal models of inflammation. These NFA effects are mediated by targeting important regulatory proteins involved in inflammatory processes, such as 5-lipoxygenase, soluble epoxide hydrolase, or NF-κB. In the present study, we investigated the anti-tumorigenic effects of NFAs on colorectal cancer (CRC) cells in cell culture-based experiments and in a murine xenograft model of human CRC. We could show that 9-NOA suppresses the viability of CRC cells (HCT-116 and HT-29) by inducing a caspase-dependent apoptosis via the intrinsic apoptotic pathway. Co-treatment with the pan-caspase inhibitor Q-VD-OPH counteracted the NFA-mediated apoptosis in both cell lines. Furthermore, NFAs affected the cell cycle transition and reduced the oxygen consumption rate (OCR) immediately. On the contrary to their well-known anti-oxidative properties, NFAs mediated the generation of mitochondrial oxidative stress in human CRC cells. Additionally, similar to the cytostatic drug mitomycin, 9-NOA significantly reduced tumor growth in a murine xenograft model of human colorectal cancer. In contrast to the established cytostatic drug, 9-NOA treatment was well tolerated by mice. This study delivers a novel mechanistic approach for nitro-fatty acid-induced inhibition of CRC cell growth by targeting mitochondrial functions such as the mitochondrial membrane potential and mitochondrial respiration. We suggest these naturally occurring lipid mediators as a new class of well tolerated chemotherapeutic drug candidates for treatment of CRC or potentially other inflammation-driven cancer types

Michael acceptor containing drugs are a novel class of 5-lipoxygenase inhibitor targeting the surface cysteines C416 and C418

Recently, we published that nitro-fatty acids (NFA) are potent electrophilic molecules which inhibit 5-lipoxygenase (5-LO) by interacting catalytically with cysteine residues next to a substrate entry channel. The electrophilicity is derived from an intramolecular Michael acceptor moiety consisting of an electron-withdrawing group in close proximity to a double bond. The potential of the Michael acceptor moiety to interact with functionally relevant cysteines of proteins potentially renders them effective and sustained enzyme activity modulators. We screened a large library of naturally derived and synthetic electrophilic compounds to investigate whether other types of Michael acceptor containing drugs suppress 5-LO enzyme activity. The activity was measured by assessing the effect on the 5-LO product formation of intact human polymorphonuclear leukocytes. We demonstrated that a number of structurally different compounds were suppressive in the activity assays and showed that Michael acceptors of the quinone and nitro-alkene group produced the strongest inhibition of 5-LO product formation. Reactivity with the catalytically relevant cysteines 416 and 418 was confirmed using mutated recombinant 5-LO and mass spectrometric analysis (MALDI-MS). In the present study, we show for the first time that a number of well-recognized naturally occurring or synthetic anti-inflammatory compounds carrying a Michael acceptor, such as thymoquinone (TQ), the paracetamol metabolite NAPQI, the 5-LO inhibitor AA-861, and bardoxolone methyl (also known as RTA 402 or CDDO-methyl ester) are direct covalent 5-LO enzyme inhibitors that target the catalytically relevant cysteines 416 and 418

Suzuki-Miyaura Cross-Coupling of Unprotected, Nitrogen-Rich Heterocycles: Substrate Scope and Mechanistic Investigation

The Suzuki-Miyaura cross-coupling of unprotected, nitrogen-rich heterocycles using precatalysts P1 or P2 is reported. The procedure allows for the reaction of variously substituted indazole, benzimidazole, pyrazole, indole, oxindole, and azaindole halides under mild conditions in good to excellent yields. Additionally, the mechanism behind the inhibitory effect of unprotected azoles on Pd-catalyzed cross-coupling reactions is described based on evidence gained through experimental, crystallographic, and theoretical investigations.National Institutes of Health (U.S.) (Award GM46059)German Science Foundation (Postdoctoral Fellowship