Recent advances in copper-catalyzed asymmetric coupling reactions

Copper-catalyzed (or -mediated) asymmetric coupling reactions have received significant attention over the past few years. Especially the coupling reactions of aryl or alkyl halides with nucleophiles became a very powerful tool for the formation of C–C, C–N, C–O and other carbon–heteroatom bonds as well as for the construction of heteroatom-containing ring systems. This review summarizes the recent progress in copper-catalyzed asymmetric coupling reactions for the formation of C–C and carbon–heteroatom bonds

Synthesis of [1,2,3]Triazolo[1,5-<i>a</i>]quinoxalin-4(5<i>H</i>)-ones through Copper-Catalyzed Tandem Reactions of <i>N</i>-(2-Haloaryl)propiolamides with Sodium Azide

A simple and efficient approach for the synthesis of [1,2,3]triazolo[1,5-<i>a</i>]quinoxalin-4(5<i>H</i>)-ones is described. The methodology is based on a tandem reaction of 1-(2-haloaryl)propiolamides with sodium azide through a [3 + 2] azide–alkyne cycloaddition and intramolecular Ullmann-type C–N coupling process

Targeting of N-Type Calcium Channels via GABAB-Receptor Activation by α-Conotoxin Vc1.1 Variants Displaying Improved Analgesic Activity

α-Conotoxins exhibiting analgesic activity, such as Vc1.1, have been shown to inhibit α9α10 nicotinic acetylcholine receptors (nAChRs) and GABAB-receptor (GABABR) coupled N-type (CaV2.2) calcium channels. Here, we report two Vc1.1 variants, Vc1.1[N9R] and benzoyl-Vc1.1[N9R], that selectively inhibit CaV2.2 channels via GABABR activation but exhibit reduced inhibitory activity at α9α10 and other neuronal nAChR subtypes compared with Vc1.1. Surprisingly, the analgesic activity of Vc1.1[N9R] and benzoyl-Vc1.1[N9R] was more potent than that of Vc1.1 when tested in partial sciatic nerve ligation injury and chronic constriction injury models. Vc1.1[N9R] and benzoyl-Vc1.1[N9R] exhibited either similar or tenfold higher activity of GABABR-mediated CaV2.2 inhibition but no activity at CaV2.2 alone; however, the mechanism of increased analgesic activity is unknown. The effects on analgesic activity and α9α10 nAChR of other Vc1.1 variations at position 9 and the N-terminus were also determined. Our findings provide new insights for designing potent inhibitors for GABABR-coupled N-type (CaV2.2) calcium channels

Cloning, Synthesis and Functional Characterization of a Novel α-Conotoxin Lt1.3

α-Conotoxins (α-CTxs) are small peptides composed of 11 to 20 amino acid residues with two disulfide bridges. Most of them potently and selectively target nicotinic acetylcholine receptor (nAChR) subtypes, and a few were found to inhibit the GABAB receptor (GABABR)-coupled N-type calcium channels (Cav2.2). However, in all of α-CTxs targeting both receptors, the disulfide connectivity arrangement “C1-C3, C2-C4” is present. In this work, a novel α4/7-CTx named Lt1.3 (GCCSHPACSGNNPYFC-NH2) was cloned from the venom ducts of Conus litteratus (C. litteratus) in the South China Sea. Lt1.3 was then chemically synthesized and two isomers with disulfide bridges “C1-C3, C2-C4” and “C1-C4, C2-C3” were found and functionally characterized. Electrophysiological experiments showed that Lt1.3 containing the common disulfide bridges “C1-C3, C2-C4” potently and selectively inhibited α3β2 nAChRs and not GABABR-coupled Cav2.2. Surprisingly, but the isomer with the disulfide bridges “C1-C4, C2-C3” showed exactly the opposite inhibitory activity, inhibiting only GABABR-coupled Cav2.2 and not α3β2 nAChRs. These findings expand the knowledge of the targets and selectivity of α-CTxs and provide a new structural motif to inhibit the GABABR-coupled Cav2.2

Copper-Catalyzed Desymmetric Intramolecular Ullmann C–N Coupling: An Enantioselective Preparation of Indolines

The first highly enantioselective copper-catalyzed intramolecular Ullmann C–N coupling reaction has been developed. The asymmetric desymmetrization of 1,3-bis­(2-iodoaryl)­propan-2-amines catalyzed by CuI/(R)-BINOL-derived ligands led to the enantioselective formation of indolines in high yields and excellent enantiomeric excesses. This method was also applied to the formation of 1,2,3,4-tetrahydroquinolines in high yields and excellent enantioselectivity

Copper-Catalyzed Desymmetric Intramolecular Ullmann C–N Coupling: An Enantioselective Preparation of Indolines

The first highly enantioselective copper-catalyzed intramolecular Ullmann C–N coupling reaction has been developed. The asymmetric desymmetrization of 1,3-bis­(2-iodoaryl)­propan-2-amines catalyzed by CuI/(R)-BINOL-derived ligands led to the enantioselective formation of indolines in high yields and excellent enantiomeric excesses. This method was also applied to the formation of 1,2,3,4-tetrahydroquinolines in high yields and excellent enantioselectivity

Inhibition of Dot1L Alleviates Fulminant Hepatitis Through Myeloid-Derived Suppressor CellsSummary

Background &amp; Aims: Fulminant hepatitis (FH) is a clinical syndrome characterized by sudden and severe liver dysfunction. Dot1L, a histone methyltransferase, is implicated in various physiologic and pathologic processes, including transcription regulation and leukemia. However, the role of Dot1L in regulating inflammatory responses during FH remains elusive. Methods: Propionibacterium acnes (P. acnes)-primed, lipopolysaccharides (LPS)-induced FH was established in C57BL/6 mice and was treated with the Dot1L inhibitor EPZ-5676. Myeloid derived suppressor cells (MDSCs) were depleted by anti-Gr-1 antibody to evaluate their therapeutic roles in Dot1L treatment of FH. Moreover, peripheral blood of patients suffered with FH and healthy controls was collected to determine the expression profile of Dot1L-SOCS1-iNOS axis in their MDSCs. Results: Here we identified that EPZ-5676, pharmacological inhibitor of Dot1L, attenuated the liver injury of mice subjected to FH. Dot1L inhibition led to decreased T helper 1 cell response and expansion of regulatory T cells (Tregs) during FH. Interestingly, Dot1L inhibition didn’t directly target T cells, but dramatically enhanced the immunosuppressive function of MDSCs. Mechanistically, Dot1L inhibition epigenetically suppressed SOCS1 expression, thus inducing inducible nitric oxide synthase (iNOS) expression in a STAT1-dependent manner. Moreover, in human samples, the levels of Dot1L and SOCS1 expression were upregulated in MDSCs, accompanied by decreased expression of iNOS in patients with FH, compared with healthy controls. Conclusions: Altogether, our findings established Dot1L as a critical regulator of MDSC immunosuppressive function for the first time, and highlighted the therapeutic potential of Dot1L inhibitor for FH treatment