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Eight previously undescribed compounds, including four alkaloids and five styryllactones together with 36 known compounds were isolated from the twig and leaf extracts of Goniothalamus cheliensis. Their structures were elucidated by extensive analysis of their spectroscopic data. The absolute configuration of (−)-(4S,5S,6R,7S,8S)-goniochelienlactone and (−)-(4S,5S,6R,7S,8S)-7-acetylgoniochelienlactone were established from single crystal X-ray analysis using Cu Kα radiation. The absolute configurations of the other related compounds were identified by comparisons of their ECD spectra with those of related known compounds. Most of the isolated compounds were evaluated for their cytotoxicities against human colorectal cancer cells (HCT-116). Griffithazanone A was the most potent with an IC50 value of 2.39 μM.

Organic molecular hole-transport materials (HTMs) are appealing for the scalable manufacture of perovskite solar cells (PSCs) because they are easier to reproducibly prepare in high purity than polymeric and inorganic HTMs. There is also a need to construct PSCs without dopants and additives to avoid formidable engineering and stability issues. We report here a power conversion efficiency (PCE) of 20.6% with a molecular HTM in an inverted (p–i–n) PSC without any dopants or interlayers. This new benchmark was made possible by the discovery that, upon annealing, a spiro-based dopant-free HTM (denoted DFH) containing redox-active triphenyl amine (TPA) units undergoes preferential molecular organization normal to the substrate. This structural order, governed by the strong intermolecular interactions of the DFH dioxane groups, affords high intrinsic hole mobility (1 × 10−3 cm2 V−1 s−1). Annealing films of DFH also enables the growth of large perovskite grains (up to 2 μm) that minimize charge recombination in the PSC. DFH can also be isolated at a fraction of the cost of any other organic HTM.

Indolizine derivatives are obtained by irradiation of 2-benzoyl-N-benzylpyridinium derivatives and dimethyl acetylene dicarboxylate, thus providing a competitive and complementary base- and catalyst-free synthesis. With this method, the first example of a crystallochromic indolizine is presented, whose color in the solid state depends on the out-of-plane torsion of the benzoyl substituent.

Ammonium and potassium salts featuring the chiral mer-[P(C6H4CO2)3]−, mer-[1]−, have been isolated. Specifically, treating phosphorane P(C6H4CO2)2(C6H4CO2H), 2, with N-containing bases [Nbase = PhN...

Here we report a scalable synthesis of the key amino acid residue, (2

Redox noninnocent ligands enhance the reactivity of the metal they complex, a strategy used by metalloenzymes and in catalysis. Herein, we report a series of copper complexes with the same ligand framework, but with a pendant nitrogen group that spans five different redox states between nitro and amine. Of particular interest is the synthesis of a unprecedented copper(I)-arylhydroxylamine complex. While hydroxylamines typically disproportionate or decompose in the presence of transition metal ions, the reactivity of this metastable species is arrested by the presence of an intramolecular hydrogen bond. Two-electron oxidation yields a copper(II)-(arylnitrosyl radical) complex that can dissociate to a copper(I) species with uncoordinated arylnitroso. This combination of ligand redox noninnocence and hemilability provides opportunities in catalysis for two-electron chemistry via a one-electron copper(I/II) shuttle, as exemplified with an aerobic alcohol oxidation.

Three undescribed spirosteroids, asparacemosones A–C, an undescribed spiro-21-norsteroid, asparacemosone D, along with seven known compounds were isolated from Thai herbal plant Asparagus racemosus Willd. roots. Their structures were elucidated by spectroscopic analysis including NMR, UV, IR and mass spectrometry. The absolute configurations of asparacemosones A, B, and D were determined by single crystal X-ray diffraction using CuKα radiation. Among the isolated compounds, the norlignan nyasol and three acetylenic norlignans demonstrated potent α-glucosidase inhibition, with IC50 values ranging from 0.003 to 0.004 μM which is 5 × 104 fold more potent than the standard acarbose.

It was demonstrated that styrylquinolizinium derivatives may be applied as photoswitchable DNA ligands. At lower ligand:DNA ratios (≤1.5), these compounds bind to duplex DNA by intercalation, with binding constants ranging from Kb = 4.1 × 104 M to 2.6 × 105 M (four examples), as shown by photometric and fluorimetric titrations as well as by CD and LD spectroscopic analyses. Upon irradiation at 450 nm, the methoxy-substituted styrylquinolizinium derivatives form the corresponding syn head-to-tail cyclobutanes in a selective [2 + 2] photocycloaddition, as revealed by X-ray diffraction analysis of the reaction products. These photodimers bind to DNA only weakly by outside-edge association, but they release the intercalating monomers upon irradiation at 315 nm in the presence of DNA. As a result, it is possible to switch between these two ligands and likewise between two different binding modes by irradiation with different excitation wavelengths.

H4octox, a versatile new octadentate acyclic chelating ligand, has been investigated as an alternative to the acyclic DTPA and the macrocyclic DOTA for trivalent metal ions useful in diagnostic medical imaging or therapeutic applications (Y3+, In3+, La3+, Gd3+, Lu3+). The synthesis of H4octox is straightforward in less steps and thus more economical than those of most previously reported chelators. Complex formation equilibria in the presence of Y3+, In3+, La3+, Gd3+, and Lu3+ revealed fast chelation and high metal-sequestering capacity. Quantitative labeling with 111In3+ was achieved within 15 min at room temperature at ligand concentrations as low as 10–7 M, exactly the properties required for the development of kit-based radiopharmaceuticals. In vitro serum stability studies and in vivo SPECT imaging confirmed excellent complex stability of [111In(octox)]−. Moreover, it is more lipophilic than most of the multidentate carboxylate- or picolinate-based chelators; it therefore shows more liver clearance a...

Attempts to selectively oxidize mustard gas [(ClCH2CH2)2S, abbreviated as BCES] to the non-toxic sulfoxide using a trans-Ru(TMP)(O)2/O2 catalyst (TMP = porphyrin dianion of 5,10,15,20-tetramesitylporphyrin) have led to isolation and characterization, including an X-ray structure, of trans-Ru(TMP)(BCES)2, the first such report of a metal-mustard gas complex.

Nickel-catalyzed catalyst transfer polycondensation (CTP) of thiophenes is an efficient strategy for the controlled synthesis of polythiophenes. However, a detailed view of its reaction mechanism has remained elusive with unresolved questions regarding the geometry and bonding of critical Ni(0) thiophene intermediates. Herein, we provide experimental and computational evidence of structurally characterized square planar η2-Ni(0)–thiophene species and their relevance to the mechanism of CTP. These results confirm the viability of C,C-η2 bound intermediates in CTP of thiophenes, providing an electronic rationale for the stability of such species, and thus that such processes can proceed as living polymerizations. We further show that C,S-κ2 species may also be relevant in nickel-catalyzed CTP of thiophenes, providing new avenues for exploitation and optimization. The mechanism for nickel-catalyzed catalyst transfer polycondensation of thiophenes to polythiophenes. Here the authors show experimental and computational evidence of structurally characterized square planar η2-Ni(0)–thiophene species and their relevance to the mechanism of catalyst transfer polycondensation.

Kinetically stabilized 1-phosphahaloprenes (2-halo-1-phosphabutadienes) as well as 1-phosphaisoprene undergo a hitherto unknown phospha-Diels-Alder dimerization of the P[double bond, length as m-dash]C-C[double bond, length as m-dash]C units upon heating. The [4+2] cyclodimerization is highly stereo- and regio-selective. The phosphaalkene-substituted phosphacyclohexene product is an unprecedented P(sp

An acyclic hexadentate oxine-derived chelating ligand, H2hox, was investigated as an alternative to current chelators for 68Ga. The straightforward preparation of H2hox, involving only one or two steps, obviates the synthetic challenges associated with many reported 68Ga chelators; it forms a Ga3+ complex of great stability (log K = 34.4) with a remarkably high gallium scavenging ability (pGa3+ = −log[Ga3+free] = 28.3, ([Ga3+] = 1 μM; [Lx–] = 10 μM; pH 7.4, and 25 °C)). Moreover, H2hox coordinates 68Ga quantitatively in 5 min at room temperature in ligand concentrations as low as 1 × 10–7 M, achieving an unprecedented high molar activity of 11 ± 1 mCi/nmol (407 ± 3.7 MBq/nmol) without purification, suggesting prospective kit-based convenience. [68Ga(hox)]+ showed no decomposition in a plasma challenge. Good in vivo stability and fast renal and hepatic clearance of the [68Ga(hox)]+ complex were demonstrated using dynamic positron emission tomography/computed tomography imaging. The intrinsic fluorescence o...

Metal-containing dithienylethenes offer new opportunities for variations in photochromic behavior. This work reports a series of copper(I) complexes containing dithienylethene-based bidentate phosphine ligands displaying varying photochromic properties. A copper dimer is used as a common precursor, allowing diverse photochromic functionality to be achieved. Calculations show that ring closing of the peripheral dithienyl moiety leads to a slight expansion of the five-membered metallacycle. The photochromic properties and photoreaction quantum yields of these complexes are tunable by variation of the ancillary ligands. Photoswitchable catalysis of a hydroboration reaction with one of the copper complexes is demonstrated.

α-Amanitin is an extremely toxic bicyclic octapeptide isolated from the death-cap mushroom, Amanita phalloides. As a potent inhibitor of RNA polymerase II, α-amanitin is toxic to eukaryotic cells. Recent interest in α-amanitin arises from its promise as a payload for antibody-drug conjugates. For over 60 years, A. phalloides has been the only source of α-amanitin. Here we report a synthesis of α-amanitin, which surmounts the key challenges for installing the 6-hydroxy-tryptathionine sulfoxide bridge, enantioselective synthesis of (2 S,3 R,4 R)-4,5-dihydroxy-isoleucine, and diastereoselective sulfoxidation.

Syntheses are reported for: nine 2-nitroimidazoles, the abbreviated names all beginning with E, based on derivation from Etanidazole); five 2-methyl-5-nitroimidazoles (M compounds, derived from Metronidazole); and five 2-methyl-4-nitroimidazoles (labelled 2M4N compounds). The nitroimidazoles all have an amide side-chain at the N1 atom of the imidazole, with 17 of them containing one to five halogen atoms. The aim is to study compounds for comparison with EF5 (the number showing the presence of five F-atoms), a previously reported, pentafluoropropylacetamide derivative of 2-nitroimidazole that is currently used as a hypoxia marker drug to detect cancerous tumours. The new compounds are characterized by standard methods, including X-ray structural data for the fluorinated MF5, 2M4NF5, and 2M4NF1(−1) species, with the “–1” indicating two C-atoms in an alkylamide chain rather than the three C-atoms in the propylacetamide of EF5. Intra- and inter-molecular H-bonding is seen in the solid state structures, likely an important property in biological use; another key property of the nitroimidazoles is their reduction potentials, and the measured CV data confirm that 2NO2Im compounds with longer side-chains and more F-atoms (like EF5) are worth investigating for possible activity as hypoxia-selective, bioreductive agents.

Known stable [Cr(bpy)2(Ph)2](BPh4) complexes undergo reductive elimination of biphenyl with visible-light photolysis using household incandescent or compact fluorescent light bulbs. A series of [Cr(R-bpy)2(Ar)2](X) complexes (R = H or CMe3; Ar = Ph, C6H4-CMe3, or C6H4-OMe; X = I, BPh4, or PF6) were prepared, and the effect of varying the bipyridine and aryl ligands on the UV–visible spectra and electrochemistry of the chromium(III) complexes was investigated. Photolysis of a mixture of two different bis(aryl) complexes gave only the homocoupled biaryl products by 1H NMR and gas chromatography/mass spectrometry analysis. The initial product of photoinduced reductive elimination of [Cr(bpy)2(Ar)2](PF6) was trapped with bipyridine to generate [Cr(bpy)3](PF6) and with benzoyl peroxide to form [Cr(bpy)2(O2CPh)2](PF6). The latter chromium(III) bis(benzoate) complex was also synthesized by the addition of bipyridine and PhCO2H to Cp2Cr, followed by air oxidation. The neutral Cr(bpy)(S2CNMe2)Ph2 complex also gene...

A valence isoelectronic and isostructural series of charged bis(N-heterocyclic carbene) pincer complexes [M(bC^N^bC)X]OTf and [M(bC^N^bC)CH3CN](OTf)2 (where M = Ni, Pd, and Pt, bC^N^bC = 1,1′-(pyridine-2,6-diylbis(methylene))bis(3-butylbenzo[d]imidazol-2-ylidene)) were synthesized, characterized, modelled by density functional theory calculations, and compared for their electrochemical properties and reactivity with CO2. Although the electrochemical response of each complex is altered by the presence of CO2, controlled potential electrolysis experiments demonstrated the superior ability of [Pd] to reduce CO2 to CO in faradaic efficiencies up to 58% in the presence of trifluoroacetic acid, compared to [Pt] and [Ni] which showed only marginal production of CO, giving the trend [Pd] ≫ [Pt] > [Ni] for this series.

Photocyclized intermediate formation and quasi C 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 C twisting are the dominant processes behind the AIE., Aggregation-induced emission (AIE) is the long-sought solution to the problem of aggregation-caused quenching that has hampered efficient application of fluorescent organic materials. An important goal on the way to fully understand the working mechanism of the AIE process was, for more than a decade, and still remains obtaining more comprehensive insights into the correlation between the ultrafast excited-state dynamics in tetraphenylethylene (TPE)-based molecules and the AIE effect in them. Here we report a number of TPE-based derivatives with varying structural rigidities and AIE properties. Using a combination of ultrafast time-resolved spectroscopy and computational studies, we observe a direct correlation between the state-dependent coupling motions and inhibited fluorescence, and prove the existence of photocyclized intermediates in them. We demonstrate that the dominant non-radiative relaxation dynamics, i.e. formation of intermediate or rotation around the elongated C 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 C bond, is responsible for the AIE effect, which is strongly structure-dependent but not related to structural rigidity.

Phosphoranes P(OC6H4NR)2(OC6H4NHR) [R = Me (2a), Ph (2b), C6F5 (2c)] were synthesized by treating PCl5 with the respective 2-aminophenol derivative (1a-c, 3.1 equiv.). In one instance, an intermediate species, P(OC6H4NR)2Cl [R = Me (3a)], was isolated and structurally characterized. Deprotonation of the amine moieties (-NH[combining low line]R) in phosphoranes 2a and 2b with a strong alkali-metal base (e.g. n-BuLi) in the presence of a strong-donor solvent (e.g. THF) afforded salts composed of the hexacoordinate P(v)-anions [P(OC6H4NR)3]- (R = Me, [4a]-; Ph, [4b]-). Employing precursor 2a, the salt Li(THF)3fac-[4a]- was isolated. The X-ray crystal of each enantiomer of [4a]- was determined and, to our knowledge, represents the first structurally characterized example of a salt containing a hexacoordinate P(v)N3O3 anion featuring P(v)-N bonds.

Acylboronate esters/trifluoroborates represent an elusive class of boronates that are of increasing interest for both fundamental study as well as applications at the interface of chemistry and biology. Their preparation has been limited by the use of strongly basic anions, often introduced in multistep reactions. Herein, we demonstrate the facile preparation of acylboronate N-methyliminodiacetyl (MIDA) esters from alkenyl-2-boronate esters through mild dihydroxylation and meta-periodate cleavage. Given the well-known functional-group tolerance of this mild reaction sequence and the availability of alkenyl-2-boronates, this method should greatly increase access to acylboronate MIDA esters.

Reaction of Cp*Mo(NO)Cl2 with 1 equiv of 1,2-bis(dimethylphosphino)ethane (dmpe) in THF at ambient temperature forms [Cp*Mo(NO)(Cl)(κ2-dmpe)]Cl (1), which is isolable as an analytically pure yellow powder in 65% yield. Further addition of 2 equiv of Cp2Co to 1 in CH2Cl2 affords dark red Cp*Mo(NO)(κ2-dmpe) (2), which was isolated in 36% yield by recrystallization from Et2O at −30 °C. Reaction of a benzene solution of 2 with an equimolar amount of elemental sulfur results in the immediate production of dark blue (μ-S)[Cp*Mo(NO)(κ1-dmpeS)]2 (3), which is a rare example of a bimetallic transition-metal complex bridged by only a single sulfur atom and involving Mo═S═Mo bonding. In contrast, reaction of 2 with an excess of sulfur in benzene results in the formation of Cp*Mo(NO)(η2-S2)(κ1-dmpeS) (4). Complex 4 can also be formed by the addition of elemental sulfur to 3, thereby indicating that 3 is a precursor to 4. Cp*Mo(NO)(κ2-dmpe) (2) also undergoes interesting transformations when treated with organic bromi...

The Ru III complexes, [Ru(acac) 2 L 2 ] Tf, and the Ru II complexes, Ru(hfac) 2 L 2 , have been synthesized and characterized; acac = acetylacetonate, hfac = 1,1,1,5,5,5-hexafluoroacetonate, Tf = triflate, and L = imidazole (Im) or a substituted imidazole (NMeIm, 2MeIm, 4/5MeIm, 2NO 2 Im); other nitroimidazoles, named metronidazole, etanidazole, and EF5 (a pentafluorinated derivative of etanidazole) were also used. Cis -isomers of the Ru complexes were usually formed, but some trans -isomers were also isolated. Characterization methods include NMR, UV/Vis, and MS spectroscopies, and CV data; X-ray crystallographic data were obtained for the cis -[Ru(acac) 2 L 2 ]Tf complexes (L = Im, NMeIm, 2MeIm, and 5MeIm). Interest in these complexes stems from their potential antiproliferatory activity, and use of the nitroimidazole species as radiosensitizers. More incidentally synthesized were cis -[Ru(acac) 2 L(MeCN)]Tf (L = Im, 2MeIm), cis -Ru(hfac) 2 Im(MeCN), and [Ru(hfac)(NMeIm) 4 ]PF 6 .

We introduce an air- and moisture-stable hydroxy-bridged indium salan complex as a highly active and controlled catalyst for the ring-opening polymerization of cyclic esters in air. The reversible activation of this complex with linear and branched alcohols leads to immortal polymerization, allowing the controlled formation of block copolymers in air. It is the only reported example of a living catalyst that remains controlled after multiple exposures to ambient air at high temperatures. Although the prevalent catalyst for ring-opening polymerization, tin octanoate, is robust, it does not promote controlled polymerization. Our indium catalyst is exceptional in being both robust and controlled.

As illustrated in the accompanying diagram, thermolysis of Cp*W(NO)(CH2CMe3)2 (Cp* = η5-C5Me5) at 80 °C in neat linear alkanes effects three successive C–H bond activations of the hydrocarbon substrates and forms Cp*W(NO)(H)(η3-allyl) complexes in which the allyl ligands are derived from the alkanes. These allyl hydrido compounds exist in solutions as mixtures of isomers containing monosubstituted (i.e., terminal) or 1,3-disubstituted (i.e., internal) allyl ligands which can have either an endo or exo orientation with the substituent groups being either proximal or distal to the nitrosyl ligand. Due to steric factors the most abundant isomer in all cases has a monosubstituted allyl ligand in the endo orientation with the alkyl end distal to the nitrosyl ligand. In addition, the relative abundance of Cp*W(NO)(H)(η3-allyl) isomers having monosubstituted allyl ligands decreases with increasing length of the n-alkane chain. Further thermolysis of the Cp*W(NO)(H)(η3-allyl) complexes results in the liberation o...

A C-pyrenyl poly(methylenephosphine) (Mn = 4800, Đ = 1.56) was synthesized from the anionic polymerization of a P-mesityl phosphaalkene. The phosphine oxide polymer exhibits blue fluorescence in solution (λmax 379, 400 nm, λonset 560 nm; Φ = 0.05) and blue-green fluorescence in the solid state at room temperature (λmax 460 nm, Φ = 0.07). In contrast, unoxidized polymer displays only a weak emission in solution and no emission in the solid state. Fluorescence studies of partially oxidized polymers (50, 75, 83% oxidation) indicate that “turn on” emission occurs only at very high degrees of oxidation (near 100%). We conclude that even a small number of unoxidized phosphine moieties within the partially oxidized polymer intramolecularly quench the fluorescence.

The new ansa macrolide antibiotics 1 to 4 have been isolated from cultures of a Micromonospora sp. obtained from a marine sediment. Rifamycins 1 and 2 are the first natural ansa macrolides to have a 3-amino substituent. Sporalactams A (3) and B (4) are comprised of a heterocylic core 5 and a 14-membered ansa bridge that are both unprecedented. Sporalactam B (4) shows selective and potent inhibition of Mycobacterium tuberculosis.

The synthesis and ligand-centered redox chemistry of palladium complexes bearing two potentially bidentate verdazyl ligands is explored. Reaction of 1,5-diisopropyl-3-pyridin-2-yl-6-oxoverdazyl radical 1 with Pd(NCMe)4·2BF4 gives a complex containing two coordinated verdazyl radicals. The structure of this complex consists of one verdazyl bound to Pd in a bidentate mode and the second verdazyl bound in a monodentate fashion through the pyridine substituent; the fourth coordination site is occupied by a solvent molecule (acetonitrile (3) or dimethyl sulfoxide (4)). Two-electron reduction of this complex with decamethylferrocene affords a bis(verdazyl) palladium complex (5) in which both verdazyls have been reduced to their anionic state and are both bound to Pd in bidentate manner. Complex 5 can be independently synthesized by a redox reaction between 1 and Pd2(dba)3. Reduced complex 5 can be re-oxidized to 3 or 4 with AgBF4; in contrast, oxidation with PhICl2 leads to ligand dissociation, ultimately giving radical 1 and a mono(verdazyl)dichloropalladium complex 2. One-electron oxidation using PhICl2 produces a formally “mixed valent” (in ligand) bis(verdazyl)chloropalladium complex (6) with one bidentate verdazyl anion ligand and one monodentate (pyridine-bound) verdazyl radical. Attempted protonation of the verdazyl ligands in complex 5 leads to complete ligand dissociation and protonation of both the tetrazine and pyridine moieties; deprotonation regenerates 5. Subsequent air oxidation of the tetrazane/pyridinium cation (formed as a tetrachloropalladate salt) leads to re-coordination of the verdazyl ligands to give 6 initially, but ultimately produces a combination of free radical 1 and 2.

Trivalent lanthanum (La3+) has the potential to treat bone resorption disorders (such as osteoporosis) by eliciting a bone-building response in the cells which control skeletal remodelling. Because La3+ suffers from extremely poor intestinal absorption, specifically designed chelators are required in order that a biologically active form of lanthanum can be administered orally. Two such chelators, 1,2-dimethyl-3-hydroxy-4-pyridinone (Hdpp) and bis-{[bis(carboxymethyl)amino]methy}phosphinic acid (H5XT), have previously been the subjects of extensive physical, in vitro, and in vivo testing as the tris- and mono-lanthanum(iii) complexes La(dpp)3 and La(XT), respectively. In this manuscript, we expand upon those studies to include 4-week intravenous (IV) and oral La3+ biodistribution profiles, which show that the metal ion initially accumulates in the liver followed by preferential redistribution and retention by bone. Of the two compounds, La(XT) demonstrates the more favourable in vivo characteristics, therefore dose-dependent oral biodistribution studies were carried out with this complex. These show drug saturation above a dose of 100 mg kg-1 day-1, so liver histology was performed in order to assess any potential toxicity. Finally, we improve upon the physical characterization of La(dpp)3 to include a single crystal X-ray structure, which exhibits an 8-coorindate La3+ centre with two bound water molecules, and a disordered exoclathrate-type hydrogen bonded network.

Reacting the low-valent nickel complex [(dtbpe)Ni]2(μ-η2:η2-C6H6) with oxaziridines was found to form mixtures of imine, amide and aldehyde products. If the N-substituent of the oxaziridine is sufficiently bulky, a short-lived intermediate can be isolated and characterized by X-ray diffraction studies as an oxazanickela(II)cyclobutane. This is the first well-defined example of N–O oxidative addition of an oxaziridine to a transition metal. Subsequent fragmentation of this oxazanickelacyclobutane forms a complex mixture of products, including a nickel(II) imido complex, demonstrating that oxaziridines can serve as nitrene precursors. Preliminary mechanistic analysis is consistent with a bimetallic mechanism of fragmentation of the oxazanickelacyclobutane to form the nickel imido and η2-aldehyde complexes.

H4octapa is an extremely versatile acyclic chelator for a wide variety of medicinally relevant metal ions, forming complexes of both high thermodynamic and kinetic stability. This work reports a significantly simplified 3 step high yield straightforward synthesis of H4octapa directly from EDDA. Crystals of the octa-protonated form of the ligand [H8octapa]4+ as its tetrachloride salt, and of the mixed lanthanum-sodium salt of [La(octapa)]- were isolated and characterized by X-ray diffraction. All eight protonation constants for the ligand were determined through combined potentiometric-spectrophotometric titrations and in batch experiments using UV spectrophotometry and 1H NMR spectroscopy. Synthesis, characterisation and solution equilibria studies are presented for complexes [Ln(octapa)]- (Ln = lanthanide element) with Sm(iii), Dy(iii), and Yb(iii) (each of which have radiopharmaceutical applications). Complex formation equilibria studies provided evidence of Ln(Hoctapa), [Ln(octapa)]- and [Ln(octapa)(OH)]2- species in solution, and their stability constants were evaluated by pH-potentiometric competition titrations using [ttha]6- as a competing ligand, and by UV-vis spectrophotometric measurements. The high stability constants of the [Ln(octapa)]- complexes with Sm(iii), Dy(iii), and Yb(iii) (log KSmL = 20.10(2), log KDyL = 20.14(3) and log KYbL = 19.90(1)) are similar to the published values for other lanthanides and consequently these initial investigations confirm H4octapa as a valuable ligand for Sm(iii), Dy(iii), Yb(iii) and other Ln for application in diagnostic and therapeutic nuclear medicine.

The development of solid, weighable Bronsted acids featuring the hexacoordinated phosphorous(V) anion [TRISPHAT]− are reported. H(DMF)2[1] and H(THF)2[1] {[1]− = [P(1,2-O2C6Cl4)3]−} were synthesized and fully characterized by 1H, 31P, 13C and 2D-NOESY NMR spectroscopy, X-ray crystallography, mass spectrometry and elemental analysis. Both, H(DMF)2[1] and H(THF)2[1] are found to be suitable initiators for the polymerization of n-butyl vinyl ether and p-methoxystyrene. Optimal polymerization results for these single-component initiators were generally obtained at −50 °C where high molecular weight polymers were isolated in high yield. 1H NMR spectroscopic analysis and dynamic light scattering of solutions of the isolated polymers provide evidence for a branched structure which presumably arises from chain transfer.

Five new tris(N-salicylaldimine) (TSAN) analogues were prepared and characterized. NMR and single-crystal X-ray diffraction studies showed that they are found in different tautomeric forms, ranging from keto-enamine to enol-imine, with two showing intermediate behavior. We present a simple structural model governing the relative stability of the keto-enamine versus enol-imine tautomeric form of TSANs, based on experimental and theoretical findings on the new and existing TSAN analogues. Examination of electron delocalization throughout this range reveals a connection between tautomeric state and whether the substituent is σ or π electron withdrawing/donating. This can be used as a qualitative guide to design TSANs with controlled tautomeric behavior. These results will be helpful to the growing number of researchers in supramolecular chemistry who use TSANs to construct new materials and cages.

Reaction of Ph2 SbCl3 with 2,2'-bipyridine and Me3 SiOSO2 CF3 releases chlorobenzene, which is interpreted as a reductive (SbV /SbIII ) elimination from a complex of a stiboranium cation. Conversely, reactions of Ph2 SbCl3 with 4-methylpyridine-N-oxide and AgOSO2 CF3 give redox-resistant complexes with the generic formulae [Ph2 SbCl3-x Lx+1 ][OTf]x , including a compound containing a pnictogen(V) trication.

We report well-defined Ti(III) metallocene complexes Cp*2TiMe (1Me) and Cp*2TiH (1H) (Cp* = η5-C5Me5) as the first isolable early transition metal precatalysts for the dehydropolymerization of amine-boranes RNH2·BH3. These earth-abundant metal catalysts combine high activity with broad substrate scope. In contrast to late transition metal catalysts, 1Me displays reactivity toward a variety of primary amine-boranes, including those containing reactive moieties such as olefinic groups. The ability to functionalize the side chain of the resultant polyaminoborane [RNH-BH2]n provides a promising method for controlling properties. Mechanistic investigation of the dehydrogenation of secondary amine-borane Me2NH·BH3 supports a bond-metathesis/β-hydride elimination, redox-neutral mechanism with a Ti(III)-H resting state.

Indole dearomatization of tryptophan represents a key approach in the synthesis of indole containing alkaloids. Although the reactivity of C-3a-bromo-, 3a-iodo-, and 3a-chloropyrroloindolines has been explored, the utility and reactivity of C-3a-fluoropyrroloindolines has remained untapped. Here we induce the C-F bond to undergo a S

A new bis(pyrazolyl)dihydridoborato diphenylplatinum(ii) complex was found to react with methanol to form H2 and a new diphenylplatinum(ii) complex supported by bis(pyrazolyl)dimethoxyborate. When performed in CD3OD, in addition to the expected installation of OCD3 fragments on the B-center and concomitant formation of H-D, deuteration of PtII(C6H5)2 fragments was observed. In contrast, dissolution of the bis(pyrazolyl)dimethoxyborato diphenylplatinum(ii) complex in CD3OD led to neither deuteration of PtII(C6H5)2 fragments nor substitution of B-bound methoxy fragments. A mechanism discussing the role of the PtII-center is presented.

The chromatographic separation of the components of the acetone extract of

Four new chalcones (1, 10, 13, and 14), a new flavanone, (9), a new amide (8), and 19 known compounds were acquired from Melodorum siamensis. The structures were established by NMR and MS data analyses. Compounds 1 (er 1.4:1) and 2 (er 1.1:1) were scalemic and were resolved to yield (-)-1 and (+)-1 and (-)-2 and (+)-2, respectively. The absolute configurations of these compounds were determined from experimental and calculated ECD data. The structures and configurations of (-)-2 and (+)-8 were identified by single-crystal X-ray diffraction analysis. Compound 11 showed nuclear factor-κB inhibitory effects (IC50 = 9 μM) in a pancreatic β cell line (MIN-6 cells).

Four new compounds, (+)-(2S)-desmosdumosone (1), (+)-(2R)-7,8-dimethoxy-5-hydroxyflavanone (7), (+)-(2R)-7-methoxychamanetin (9), and (+)-(1ˊR,2ˊR)-phebalosin (18), and 25 known compounds were isolated from the twig and leaf extracts of Desmos dumosus. Compounds (±)-7 and (±)-9 were isolated as racemates and their enantiomers were separated by chiral HPLC. Their structures were elucidated by spectroscopic methods as well as comparisons made from the literature. The absolute configuration of (+)-(1ʹR,2ʹR)-18 was established by X-ray diffraction analysis using Cu Kα radiation and electronic circular dichroism (ECD) spectoscopy. In contrast, the absolute configuration of compounds (+)-(2S)-1, (+)-(2R)-7, and (+)-(2R)-9 were identified by comparing their ECD spectra and specific rotations with those of reported known compounds. Compounds 9, 11, 13, 14, 22, 25, and 28 showed α-glucosidase inhibitory activities with IC50 values ranging from 5.3-52.7 μM, much better than that of standard control (acarbose, IC50 value 83.5 μM). Compound 13 was the most active with an IC50 value of 5.3 μM., Desmos dumosus; Annonaceae; Flavonoids; α-Glucosidase inhibitory activity

Cp*W(NO)(CH2CMe3)(η3-CH2CHCHPh) (1) effects C(sp3)–H activations of methane, ethane, propane, and n-butane exclusively at their terminal carbons and forms the corresponding Cp*W(NO)(alkyl)(η3-CH2CHCHPh) complexes. It also activates (n-Bu)2O, 1-chloropropane, and Me4Si in a similar manner. Exposure of the Cp*W(NO)(alkyl)(η3-CH2CHCHPh) complexes to carbon monoxide results in initial 1,1-CO insertion into the newly formed tungsten–alkyl bonds and formation of the corresponding η1-acyl complexes, some of which can be isolated. Additional functionalization of the C–H activation products occurs upon exposure to CO under more forcing conditions. Such treatment produces η2-bound unsaturated-ketone complexes resulting from CO insertion into the W–alkyl σ bonds followed by cross-coupling of the η1-acyl and the η3-allyl ligands and coordination of CO at the resulting vacant coordination site at tungsten. The unsaturated ketones can be released from the metal’s coordination spheres either by photolysis of the complex...