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Plutonium(IV) oxalate hexahydrate (Pu(C2O4)2∙6H2O; PuOx) is an important intermediate in the recovery of plutonium from used nuclear fuel. Its formation via precipitation is well studied, yet its crystal structure remains unknown. Instead, the crystal structure of PuOx is assumed to be isostructural with neptunium(IV) oxalate hexahydrate (Np(C2O4)¬2∙6H2O; NpOx) and uranium(IV) oxalate hexahydrate (U(C2O4)¬2∙6H2O; UOx) despite the high degree of unresolved disorder that exists when determining water positions in the crystal structures of the latter two compounds. Such assumptions regarding the isostructural behavior of the actinide elements have been used to predict the structure of PuOx for use in a wide range of studies. Herein, we report the first crystal structures for PuOx and Th(C2O4)2·6H2O (ThOx). This data, along with new characterization of UOx and NpOx, has resulted in the full determination of the structures and resolution of the disorder around the water molecules. Specifically, we identify the coordination of two water molecules with each metal center, which necessitates a change in oxalate coordination mode from axial to equatorial that has not been reported in the literature. The results of this work exemplify the need to revisit previous assumptions regarding fundamental actinide chemistry, which are heavily relied upon within the current nuclear field.

A generalizable synthetic method creates a new class of covalently connected, self-threaded fluorescent molecular probes with figure-eight topology, an encapsulated deep-red fluorophore, and two peripheral peptide loops. The globular molecular shape and rigidified peptide loops enhance imaging performance by promoting water solubility, eliminating probe self-aggregation, and increasing probe stability. Moreover, the peptide loops determine the affinity and selectivity for targets within complex biological samples such as cell culture, tissue histology slices, or living subjects. For example, a probe with cell penetrating peptide loops targets the surface of cell plasma membranes; whereas, a probe with bone targeting peptide loops selectively stains the skeleton within a living mouse. The unique combination of bright deep-red fluorescence, high stability, and predictable peptide-based targeting is ideal for photon intense fluorescence microscopy and biological imaging.

A family of six homoleptic [CuI (Ln )]2 (ClO4 )2 and six heteroleptic [CuI (Ln )(PPh3 )2 ]2 (ClO4 )2 bimetallic complexes, in which Ln are bis-Schiff base ligands with alkyl spacers of variable length (n=2-7 -CH2 -), were prepared to evaluate the role of the spacer on the formation of helicates or mesocates. In the homoleptic series, spectroscopic and theoretical studies indicate that preferences for a conformation are based on energetic parameters, mainly, the establishment of noncovalent interactions. The odd-even nature of the spacers preconditions the superposition of the aromatic rings to allow the juxtaposition necessary for noncovalent interactions, whereas the increase of the length reduces the strength of such interactions. Consequently, complexes with even-spacers of short length were identified as helicates in solution, [CuI (Ln )]22+ (n=2, 4). Complexes [CuI (Ln )]22+ (n=3-7) dissociate in solution to produce the monometallic complexes in equilibrium, [CuI (Ln )]+ . The stability of the bimetallic species is discussed in terms of their conformations. The set of heteroleptic complexes was prepared to evaluate the reach of the "odd-even rule" in the solid, which is based on the "zig-zag" arrangements of the spacers. Based on crystallographic information, "S-" and "C"-type conformations of Ln are related to even and odd spacers, respectively. This trend is considered in addition to other factors to explain preferences for either a mesocate or helicate conformation in the homoleptic series.

Stabilized with an NHC ligand of the smallest steric profile, Pd(II)(²-O)(IMe) was synthesized by direct addition of dioxygen to Pd(0)(IMe). The peroxido palladium complex with IMe, which was previously available by only computation, was characterized with IR and X-ray crystallography. Moreover, its oxo-atom transfer reactivity was elucidated by studying 1) thermolysis in pyridine at 60°C to yield IMeO, and 2) reaction with oxygen atom transfer (OAT) acceptors such as PPh and (MeSi).

Two Zn-based metal-organic frameworks (Zn-MOFs) were solvothermally synthesized using two pyridine-based carboxylate linkers to generate unique pore topologies, as evidenced by single-crystal XRD analysis. These Zn-MOFs provided coordinatively unsaturated Zn2+ sites with square-pyramidal geometry, leading to an enhanced interaction with CO2, as demonstrated by sub-atmospheric pressure isotherms. The presence of open Zn2+ sites in these MOFs was validated by Raman spectroscopy under atmospheric CO2, revealing the presence of CO2 chemisorbed on surface sites. Additionally, in situ DRIFT spectra of chemisorbed acetic acid provided evidence for the formation of acetate-Zn2+ species after adsorption compared to IRMOF-1, which showed only physisorbed acetic acid species.

Bacterial biofilms pose a significant challenge in clinical environments due to their inherent lack of susceptibility to antibiotic treatment. It is widely recognized that most pathogenic bacterial strains in the clinical setting persist in the biofilm state, and are the root cause of many recrudescent infections. Discovery and development of compounds capable of either inhibiting biofilm formation or initiating biofilm dispersal may provide new therapeutic avenues for reducing the number of hospital acquired, biofilm-mediated infections. We now report the application of our recently reported image-based, high-throughput screen to the discovery of microbially-derived natural products with biofilm inhibitory activity against Vibrio cholerae. Examination of a prefractionated library of microbially-derived marine natural products has lead to the identification of a new biofilm inhibitor that is structurally unrelated to previously reported inhibitors and is one of the most potent inhibitors reported to date against V. cholerae. Combination of this compound with sub-MIC concentrations of a number of clinically relevant antibiotics was shown to improve the biofilm inhibitory efficacy of this new compound compared to monotherapy treatments, and provides evidence for the potential therapeutic benefit of biofilm inhibitors in treating persistent biofilm-mediated infections.

Atom hopping: A chlorophosphite-mediated Beckmann ligation of oximes and p-toluenesulfonyl azide gives access to N-sulfonyl phosphoramidines in good to excellent yields. The reaction proceeds under exceptionally mild conditions and constitutes a bioorthogonal approach toward amidines by avoiding the use of amines and transition-metal catalysts. dmp-ol=3,3-dimethylpropanediol.

We describe a polymer-supported stereoselective synthesis of the (1S,5S)-6-oxa-3,8-diazabicyclo[3.2.1]octane-bridged scaffold by tandem iminium ion cyclization/nucleophilic addition reactions. A series of resin-bound acyclic intermediates bearing different substituents were prepared, and the scope and limitations of the chemical route leading to the bridged scaffold were evaluated. The Thr-derived bridged scaffold was found to be substantially more stable in acid than the Ser-derived scaffold, which was partially transformed into dihydropyrazinones. Substitution at the iminium-forming nitrogen was critical for acid stability, and the N-arylsulfonamides with electron-withdrawing groups yielded the highest purity of the crude products prepared by acid-mediated cleavage. The acid-labile target compounds were synthesized by nucleophile-mediated cleavage from the esterified Wang resin and cyclization in formic acid.

The first neutron diffraction study of a single crystal containing uranyl peroxide nanoclusters is reported for pyrophosphate-functionalized Na44K6[(UO2)24(O2)24(P2O7)12][IO3]2·140H2O (1). Relative to earlier X-ray studies, neutron diffraction provides superior information concerning the positions of H atoms and lighter counterions. Hydrogen positions have been assigned and reveal an extensive network of H-bonds; notably, most O atoms present in the anionic cluster accept H-bonds from surrounding H2O molecules, and none of the surface-bound O atoms are protonated. The D4h symmetry of the cage is consistent with the presence of six encapsulated K cations, which appear to stabilize the lower symmetry variant of this cluster. 31P NMR measurements demonstrate retention of this symmetry in solution, while in situ 31P NMR studies suggest an acid-catalyzed mechanism for the assembly of 1 across a wide range of pH values.

(Et2NH2)2[CuCl4] crystallizes in the orthorhombic space group P212121 with Z = 8 (single crystal XRD).

The Diels-Alder dimer of cyclopentadiene carboxylate, Thiele's acid has conformational properties that make it attractive as a molecular scaffold for applications in supramolecular and biological chemistry. However, a lack of known reaction methodology for derivatives of Thiele's acid (or the corresponding esters) has hampered its utilization in these fields. We describe an improved preparation of Thiele's esters and survey the chemistry of these versatile intermediates. As part of this effort, we also describe the synthesis of a suite of Thiele's acid (or ester) analogues spanning a broad range of cleft angles.

A series of salicylaldiminato ligands [C6H5N=CHC6H4OH (1L), 2,6-iPrC6H3N=CHC6H4OH (2L), and 2,6-iPrC6H3N=CH-3,5-tBu2C6H2OH (3L)] were treated with Bu2Mg in the presence of the appropriate solvent system to yield the crystalline compounds [(1L6Mg3)·thf] (1), [(2L2Mg·thf)] (2), and [3L2Mg] (3). The products were characterized by 1H and 13C NMR spectroscopy and single-crystal X-ray diffraction. X-ray crystallographic analysis revealed that 1 adopts a unique trimeric aggregation state consisting of six-coordinate magnesium centers. Substitution of the ligand backbone resulted in the formation of the monomeric species 2 and 3. X-ray crystallographic analyses revealed 2 as a five-coordinate, distorted square-pyramidal magnesium complex and 3 as a four-coordinate, distorted tetrahedral species. Inspection of the metrical parameters in 1–3 indicates a decrease in the Mg–O and Mg–N bond lengths and an increase in the N–Mg–O bite angle with a decreasing coordination number at magnesium.

A NRVS single-crystal study (NRVS=nuclear resonance vibrational spectroscopy) has provided detailed information on the in-plane modes of nitrosyl iron porphyrinate [Fe(oep)(NO)] (see picture; oep=octaethylporphyrin). The axial nitrosyl ligand controls the direction of the in-plane iron motion.

Gelatinases (MMP-2 and MMP-9) have been implicated in a number of pathological conditions, including cancer and cardiovascular disease. Hence, small molecule inhibitors of these enzymes are highly sought for use as potential therapeutic agents. 2-(4-Phenoxyphenylsulfonylmethyl)thiirane (SB-3CT) has previously been demonstrated to be a potent and selective inhibitor of gelatinases, however, it is rapidly metabolized because of oxidation at the para position of the phenoxy ring and at the alpha-position to the sulfonyl group. alpha-Methyl variants of SB-3CT were conceived to improve metabolic stability and as mechanistic probes. We describe herein the synthesis and evaluation of these structural variants as potent inhibitors of gelatinases. Two (compounds 5b and 5d) among the four synthetic stereoisomers were found to exhibit slow-binding inhibition of gelatinases and MMP-14 (MT1-MMP), which is a hallmark of the mechanism of this class of inhibitors. The ability of these compounds to inhibit MMP-2, MMP-9, and MMP-14 could target cancer tissues more effectively. Metabolism of the newly synthesized inhibitors showed that both oxidation at the alpha-position to the sulfonyl group and oxidation at the para position of the terminal phenyl ring were prevented. Instead oxidation on the thiirane sulfur is the only biotransformation pathway observed for these gelatinase inhibitors.

The regioselective reaction of 2,4-dichloro-5-nitropyrimidine (I) with tertiary amines (II) and (VI) leads to pyrimidin-2-amines (III) and (VII), resp., whilst the reaction with N-methylpyrrolidine gives rise to unexpected chloride (V).

The direct access to N-acyl hydrazones is rendered possible by hexamethylphosphorous mediated condensation of various 1,2-dicarbonyl compounds with dialkylazodicarboxylates.

Upon variation of the steric and electronic properties of the starting sulfolenes four unique bi- or tricyclic ring-systems are constructed as single diastereomers with up to five stereogenic centers.

A complementary approach toward nitrone construction that circumvents a conventional condensation strategy by exploiting the unusual reactivity of 1,2-dicarbonyls with phosphines is reported.

The reaction of oximes (I) with the chlorophosphite (II) and tosyl azide is examined resulting in the formation of N-tosyl amidines through a Beckmann-type process.

The intermediate borane reagents react with carbonyl compounds to afford homoallylic and homopropargylic alcohols with low to excellent enantioselectivity.

Single crystals of (Me4N)4 [UO2(CO3)3]·8H2O are grown by slow evaporation (25 °C, 6 weeks) of an aqueous solution of uranyl 1-hydroxyethane-1,1-diphosphonate and Me4NOH.

The structures of the new uranyl and neptunyl fluoroborates are determined by single crystal XRD.

A simple and efficient method for replacing Ge atoms in deltahedral Ge94- clusters with Sb or Bi is reported.

The empty and Ni-centered Ge9 and Sn9 clusters react with TlCp and add a tenth Tl-vertex to form bicapped square antiprismatic closo-clusters [M9Tl]3- (M: Ge, Sn) and [Ni@M9Tl]3-.

The title molecule, C17H10N2O2, is a synthetic precursor to the cytotoxic marine alkaloid ascididemin and is also structurally related to cleistopholine, a plant-derived antifungal agent. The molecule was found to be essentially planar with the only significant deviations from planarity being for the quinone O atoms.

A survey of individual specimens of northern Papua New Guinea derived Cacospongia mycofijiensis has yielded novel sesquiterpenes, aignopsanoic acid A (1), methyl aignopsanoate A (2), and isoaignopsanoic acid A (3). The structures and absolute configurations of 1-3 were established using NMR data, X-ray crystallography results, and an analysis of CD properties. Two of these metabolites, 1 and 2, were moderately active against Trypanosoma brucei, the parasite responsible for sleeping sickness.

Our 2004 disclosure of the amino hemiketal-containing spiroleucettadine was met with keen interest by the natural products and synthetic communities. As repeated efforts to synthesize spiroleucettadine failed and questions regarding the original structure elucidation process arose, evidence mounted against the validity of the proposed structure. The low ratio of H/C in the core of spiroleucattadine complicated the original structure elucidation process. Speculation prompted a reisolation of spiroleucettadine from an untouched portion of the original Luecetta collection and a thorough analysis of analytical data. In addition, a systematic analysis of candidate structures was performed via density functional theory (DFT) calculations; a favored high scoring structure 1b was ultimately confirmed to be spiroleucettadine via X-ray analysis of crystalline spiroleucettadine and reinforced the validity of DFT calculations in structure elucidation. We present the revised structure of spiroleucettadine, a bicyclic sponge alkaloid with a scarcity of H-atoms in its core.

A reinvestigation of a Fijian collection of Cacospongia mycofijiensis has yielded the known mycothiazole and a novel heterocyclic, CTP-431 (1). Its structure including absolute configuration as 8R,9R,10S,13S was established using NMR data, calculated DFT 13C chemical shifts and results from X-ray crystallography. It is possible that the tricyclic skeleton of CTP-431 (1) is biosynthetically related to the macrolide latrunculin A, however the thiopyrone moiety of 1 has no previous precedent in natural products chemistry.