Qun-Li Luo

A series of novel entangled coordination frameworks with inherent features of self-threading, polyrotaxane and polycatenane

Self-assembly of transition metal salts with long aromatic dicarboxylate ligands and N-containing ligands affords a series of entangled coordination frameworks based on different metal cores, namely [Mn4(μ2-OH2)2(sdba)4(bpp)4] (1), [Mn2(sdba)2(btb)0.5(H2O)] (2), [Mn4(sdba)4(bim)(H2O)4]·2H2O (3), [Ni(sdba)(bim)(H2O)2]·2H2O (4), [Co3(sdba)2(Hsdba)2(2,2′-bpy)2] (5) and [Ni2(bpda)2(bim)2]·H2O (6) (H2sdba = 4,4′-sulfonyldibenzoic acid, H2bpda = 4,4′-carbonyldibenzoic acid, bpp = 1,3-bis(4-pyridyl)propane, btb = 1,4-bis(1,2,4-triazol-1-yl)butane, bim = 1,4-bis(imidazol-1-yl)butane, 2,2′-bpy = 2,2′-bipyridine). Their structures were determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra and TG analyses. Compound 1 is a peculiar 2D self-threading network containing unusual triflexural helical motifs, which can be rationalized as a 6-connected 2D 36-hxl (hexagonal lattice) net with double edges. Compound 2 represents the first example of a 2D polycatenated framework formed by 1D quadruple chains, which could be considered as formed by interconnected 1D polyrotaxane columns involving the unusual [3]rotaxane components. Compound 3 consists of two interlocked 2D cage-containing frameworks and exhibits an unusual (2D → 2D) parallel interpenetrating array with coexistence of polyrotaxane and polycatenane. Compound 4 is composed of two interpenetrating 2D loop-containing frameworks with 4-connected (2.65) topology, and it can also be considered as being constructed by interconnected parallel 1D polyrotaxane chains. Compound 5 is comprised of two identical 2D hydrogen-bonded layers with 6-connected (22.48.65) topology that are interpenetrated in a parallel fashion, resulting in a twofold interpenetrating net having both polyrotaxane and polycatenane characters. Compound 6 represents an unusual mode of interpenetration of two distinct 3D frames both with CdSO4 topology, which is still very rare in entangled systems. In addition, the magnetic properties of compounds 1, 3, 4, 5 and 6 are discussed.

Specificity for inhibitors of metal-substituted methionine aminopeptidase

Methionine aminopeptidases (MetAPs) have been studied in vitro as Co(II) enzymes, but their in vivo metal remains to be defined. While activation of Escherichia coli MetAP (EcMetAP1) by Co(II), Mn(II), and Zn(II) was detectable by a colorimetric Met-S-Gly-Phe assay, significant activation by Ni(II) was shown in a fluorescence Met-AMC assay, in addition to Co(II) and Mn(II) activation. When tested on the metal-substituted EcMetAP1s, a few inhibitors that we obtained recently from a random screening on Co-EcMetAP1 either became much weak or lost activity on Mn- or Zn-EcMetAP1, although they kept inhibitory activity on Ni-EcMetAP1. A couple of peptidic inhibitors and the methionine mimetic (3R)-amino-(2S)-hydroxyheptanoic acid (AHHpA, 6) maintained moderate activities on Co-, Mn-, Zn-, and Ni-EcMetAP1s. Our results clearly demonstrate that the metal-substitution has changed the enzyme specificity for substrates and inhibitors. Therapeutic applications call for inhibitors specific for MetAP with a physiologically relevant metal at its active site.

An unusual 3D 8-connected entangled coordination network with coexistence of self-threading, polythreading and interpenetration

An 8-connected entangled metal–organic framework has been synthesized and characterized, which not only represents the first entangled framework with coexistence of self-threading, polythreading and interpenetration, but also represents the highest connected topology presently known for self-threading and polythreading systems.

Metal-free sequential reaction via a propargylation, annulation and isomerization sequence for the one-pot synthesis of 2,3-disubstituted benzofurans

A metal-free one-pot synthesis of 2,3-disubstituted benzofurans is described, which allows for the reactions to be performed under ambient conditions with readily accessible propargyl alcohols and general phenols, including phenols substituted with an electron withdrawing group or a nitrogen-containing group.

Iodine-promoted Semmler-Wolff reactions: step economic access to meta-substituted primary anilines via aromatization

An atom- and step-economic access to an array of unprotected meta-substituted primary anilines was disclosed using the Semmler-Wolff reaction, promoted by molecular iodine. Therein, noble metal catalysts and inert atmosphere are unnecessary while the forcing reaction conditions and the lengthy synthesis can be avoided. The synthetic utility of this approach is evident in the de novo syntheses of three bioactive molecules with good total yields.

Access to Multisubstituted Furan-3-carbothioates via Cascade Annulation of α-Oxo Ketene Dithioacetals with Isoindoline-1,3-dione-Derived Propargyl Alcohols

A Brønsted acid-promoted, unprecedented formal (3 + 2) annulation strategy for the synthesis of multisubstituted furan-3-carbothioates is reported. This transformation represents the first regioselective annulation of α-oxo ketene dithio-acetals as 1,3-bis-nucleophiles in a cascade manner. The choice of isoindoline-1,3-dione-derived propargyl alcohols is crucial to the uncommon annulation mode between an alkyne-type bis-electrophile and a 1,3-bis-nucleophile under metal-free conditions. The scale-up of the synthesis and several interesting transformations of an as-synthesized product were further investigated. A Nazarov-like cyclization is proposed for the ring-closure process according to the experimental observations.

[2,6-Bis(5-eth­oxy-1,3-oxazol-2-yl)-4-meth­oxy­phenyl-κ3N,C1,N′]bromidopalladium(II)

In the title compound, [PdBr(C17H17N2O5)], the PdII atom is coordinated by an N,C 1,N′-tridentate pincer ligand and a Br atom in a distorted square-planar geometry. In the crystal, molecules are connected by C—H⋯Br and C—H⋯O hydrogen bonds, and π–π interactions between the oxazole and benzene rings [centroid–centroid distance = 3.7344 (19) Å], resulting in a three-dimensional supramolecular structure.