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2-Cyanoazetidines, easily accessible from β-amino alcohols, undergo ring-cleavage upon reaction with trimethylsilylazide and catalytic amounts of Bu2SnO, to give the corresponding homopropargylamines which are isolated as their N-Boc protected derivatives. The scope of this reaction, which constitutes a new way to access these highly relevant building blocks, is examined in detail. The proposed mechanism involves a tin-catalyzed cycloaddition of the nitrile moiety with the azide to give the corresponding tetrazole, which decomposes with the extrusion of two molecules of dinitrogen to produce an intermediate vinylidene carbene that finally evolves to give the alkyne.

The effect of transition metal ions and doping by isoelectronic SeO42- or PO3F2- anions on structures and structural transitions of Na2M(SO4)·2H2O (M: transition metal) are studied.

An insertion of arenes into both imides and anhydrides via reactive aryne intermediates is presented. The reaction is performed under exceptionally mild conditions, and the corresponding ketoamide products are amenable to derivatization to deliver a variety of synthetically useful motifs such as quinolones, indoles, and ketoanilines.

Functional ligand-modified polyoxotitanate (L-POT) cages of the general type [TixOy(OR)z(L)m] (OR = alkoxide, L = functional ligand) can be regarded as molecular fragments of surface-sensitized solid-state TiO2, and are of value as models for studying the interfacial charge and energy transfer between the bound functional ligands and a bulk semiconductor surface. These L-POTs have also had a marked impact in many other research fields, such as single-source precursors for TiO2 deposition, inorganic–organic hybrid material construction, photocatalysis, photoluminescence, asymmetric catalysis and gas adsorption. Their atomically well-defined structures provide the basis for the understanding of structure/property relationships and ultimately for the rational design of new cages targeting specific uses. This highlight focuses on recent advances in L-POTs research, with emphasis on their novel properties and potential applications.

We report herein an efficient synthesis of diversely substituted N-aryl-2-cyanoazetidines based on an anionic ring-closure reaction. These compounds can be prepared from β-amino alcohols in enantiomerically pure form through a three-step sequence involving (i) copper-catalyzed N-arylation, (ii) N-cyanomethylation of the secondary aniline, and (iii) one-pot mesylation followed by ring closure induced by a base. This high-yielding sequence gives access to azetidines with a predictable and adjustable substitution pattern and also with predictable diastereoselectivity. These compounds are susceptible to multiple further derivatizations through Suzuki coupling or nitrile transformation, thus appearing as valuable new scaffolds for medicinal chemistry. Their rigid shape, featuring an almost planar N-arylamine and a planar four-membered ring, was revealed by both AM1 calculations and X-ray crystallography.

Resistance to β-lactam antibiotics is mediated primarily by enzymes that hydrolytically inactivate the drugs by one of two mechanisms: serine nucleophilic attack or metal-dependent activation of a water molecule. Serine β-lactamases are countered in the clinic by several codrugs that inhibit these enzymes, thereby rescuing antibiotic action. There are no equivalent inhibitors of metallo-β-lactamases in clinical use, but the fungal secondary metabolite aspergillomarasmine A has recently been identified as a potential candidate for such a codrug. Herein we report the synthesis of aspergillomarasmine A. The synthesis enabled confirmation of the stereochemical configuration of the compound and offers a route for the synthesis of derivatives in the future.

Biological selection makes natural products promising scaffolds for drug development and the ever growing number of newly identified, structurally diverse molecules helps to fill the gaps in chemical space. Elucidating the function of a small molecule, such as identifying its protein binding partners, its on- and off-targets, is becoming increasingly important. Activity- and affinity-based protein profiling are modern strategies to acquire such molecular-level information. Introduction of a molecular handle (azide, alkyne, biotin) can shed light on the mode of action of small molecules. This Concept article covers central points on synthetic methodology for integrating a terminal alkyne into a molecule of interest.

We report that the stereochemical outcome of the conjugate addition of organocopper reagents to bicyclic α,β-unsaturated lactams derived from pyroglutaminol is determined by the nature of the aminal group. Bicyclic α,β-unsaturated lactams in which the aminal is derived from a ketone have been found to afford products of syn conjugate addition. By contrast, bicyclic α,β-unsaturated lactams in which the aminal is derived from an aldehyde afford products of anti conjugate addition. These remarkably different results obtained from very similar starting materials are unexpected.

A novel rock salt Mg0.4Fe0.6N solid solution is obtained by hot pressing a 70:30 at.% mixture of Fe and Mg together with NaN3 (MgO capsule in multianvil cell, 15 GPa, 1800 K, 1 min).

We describe herein a general and efficient synthetic approach toward substituted pyridines from functionalized N -acyl-2,3-dihydropyridones in two steps; 1,2-addition with organocerium reagents and subsequent oxidative aromatization with chloranil. This strategy allows the generation of pyridines with various substitution patterns and introduces a variety of substituents including aryl, alkyl, alkynyl, alkenyl, and heteroaryl groups at the desired positions.

Review: emphasis on recently discovered gold(III) complexes with bonds to hydrogen, oxgen, alkenes and CO ligands; 206 refs.

Herein, we review the preparation and coordination chemistry of cis and trans isomers of hyponitrite, [N2O2](2-). Hyponitrite is known to bind to metals via a variety of bonding modes. In fact, at least eight different bonding modes have been observed, which is remarkable for such a simple ligand. More importantly, it is apparent that the cis isomer of hyponitrite is more reactive than the trans isomer because the barrier of N2O elimination from cis-hyponitrite is lower than that of trans-hyponitrite. This observation may have important mechanistic implications for both heterogeneous NOx reduction catalysts and NO reductase. However, our understanding of the hyponitrite ligand has been limited by the lack of a general route to this fragment, and most instances of its formation have been serendipitous.

Molecular chaperones are key components of the arsenal of cellular defence mechanisms active against protein aggregation. In addition to their established role in assisting protein folding, increasing evidence indicates that molecular chaperones are able to protect against a range of potentially damaging aspects of protein behaviour, including misfolding and aggregation events that can result in the generation of aberrant protein assemblies whose formation is implicated in the onset and progression of neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. The interactions between molecular chaperones and different amyloidogenic protein species are difficult to study owing to the inherent heterogeneity of the aggregation process as well as the dynamic nature of molecular chaperones under physiological conditions. As a consequence, understanding the detailed microscopic mechanisms underlying the nature and means of inhibition of aggregate formation remains challenging yet is a key objective for protein biophysics. In this review, we discuss recent results from biophysical studies on the interactions between molecular chaperones and protein aggregates. In particular, we focus on the insights gained from current experimental techniques into the dynamics of the oligomerisation process of molecular chaperones, and highlight the opportunities that future biophysical approaches have in advancing our understanding of the great variety of biological functions of this important class of proteins.

We report herein a successful example of an aza-[2,3]-Wittig rearrangement in an allylic tertiary N,N-dibenzyl amine derived from (S)-alaninol or (S)-isoleucinol. This reaction occurs upon metalation at the benzylic position with a mixture of butyllithium/diisopropylamine/potassium t-butoxide and proceeds with a high 1,3 transfer of chirality.

The palladium - catalyzed aminocarbonylation of aryl tosylates with amines is reported. Suitable conditions were identified by high throughput reaction screening and then further optimized. The substrate scope of the reaction with respect to the aryl tosylate component and the amine component are reported. Competitive aminolysis of the aryl tosylates to afford the amine toluenesulfonamides and the phenol was not observed.

Polycrystalline Pb8Sb8S15Te5 is prepared by heating stoichiometric amounts of the elements (1.

Novel tetrathiafulvalene (TTF) containing compounds (III) are obtained by four-fold Stille coupling between tetrabromo-dithieno TTF (I) and stannylated thiophene (IIa) or thiazole (IIb).

Bulk preparation of graphitic C3B is achieved by thermolysis of 1,3-(BBr2)2C6H4 (evacuated silica tubes, 800 °C, 1 h; cooling rate of 5 °C/min; ≈100% yield).

A new high-yielding and direct route to the 1,2-diphospholide ligand framework using a very simple approach is presented.

In contrast to the extensively investigated β-turn conformation in peptides and proteins, single and multiple γ-turns have been much less commonly studied. Single and non-contiguous multiple γ-turns have been relatively often authenticated in small cyclic peptides, but these important peptide main-chain reversal motifs have not been examined carefully either in linear peptides or in globular proteins. This Perspective article summarizes literature data on this aspect of peptide stereochemistry, expanding the discussion also to the rarely found, contiguous multiple γ-turns which generate incipient or fully-developed 2.27-(γ-) helices. Unpublished results of recent research activities on this topic ongoing in our laboratories are also briefly outlined.

Isolated from the marine sponge Dysidea frondosa, the frondosin family of meroterpenoid natural products were shown to be antagonists of the binding of the cytokine interleukin-8 to its receptor. With implications of interleukin-8 management being associated with a wide range of acute and chronic inflammatory disorders, as well as tumor progression and/or metathesis, there have been a multitude of syntheses of these natural products in the hopes of developinging new pharmacological agents. However, assignment of the absolute configurations of these natural products became unclear, because the first two syntheses of frondosin B, by Danishefsky and by Trauner, produced conflicting assignments for the single stereogenic center at C8. Here we describe the initial stereochemical mystery surrounding the Danishefsky and Trauner syntheses and provide evidence through ensuing syntheses of frondosins B and A that resolve this issue. These subsequent asymmetric syntheses have established that (1) the natural product occurs as the R enantiomer, and (2) a late-stage stereochemical inversion occurred during the Trauner and Wright syntheses of frondosin B.

Two polar lipid-soluble macrocycles 1 and 2, containing a spiro-linked tricyclic ether ring system and an unusual seven-membered spiro-linked cyclic iminium moiety, have been isolated from the digestive glands of mussels (Mytilus edulis) and scallops (Placopecten magellanicus).

A one-pot preparation of t-butyl esters and ethers is described that proceeds from the carboxylic acid or alcohol and t-butanol using only anhydrous magnesium sulfate and catalytic sulfuric acid as additional reagents. The method affords t-butyl esters and ethers in good yields and is applicable to a variety of substrates.

Bi1-xBaxFeO3-x/2 (x = 0.2, 0.3) phases are synthesized by solid state reaction of stoichiometric mixtures of BaCO3, Bi2O3, and Fe2O3 (850—920 °C, 30—45 h, yield given in g).

A synthetic strategy towards the potent cytostatic agent pluraflavin A has been developed. Formation of the enantioenriched anthrapyran core bearing a halogen atom enabled the introduction of the α C-aryl glycoside by Stille cross-coupling and subsequent hydrogenation of the aryl glycal. Chemo- and stereoselective O-glycosylations of α oliose and β 3-epi vancosamine residues afforded a fully glycosylated aromatic core. Attempts to install the dimethylamino group of the C-disaccharide suggest that introduction of an azide group by displacement and subsequent reduction may pave the way to the total synthesis of pluraflavin A.

Metal-doped polyoxotitanium cages (M-POTs) of the type [TixOy(OR)zMnXm] (M = a main group, transition metal or lanthanide; X = an anion such as a halide) can be regarded as molecular fragments of metal-doped TiO2. As such M-POTs can be used as structural models for the inclusion of metal ions into the TiO2 lattice and the ways in which well-defined microstructural changes affect photo-induced hole–electron separation. They are also potential organically-soluble redox-catalysts for a range of organic transformations and have been shown to be useful single-source precursors for the deposition of metal-doped TiO2. The applications of M-POTs as molecular precursors to metal-doped TiO2 offers a high degree of atomic control in the low temperature fabrication of photocatalytic thin films, which have applications in pollution control and water splitting. This perspective highlights the structural trends in M-POTs, their electronic behaviour and their applications as single-source precursors, looking at current and future trends in the development of inorganic precursors for device applications.

The discovery and implementation of antibiotics in the early twentieth century transformed human health and wellbeing. Chemical synthesis enabled the development of the first antibacterial substances, organoarsenicals and sulfa drugs, but these were soon outshone by a host of more powerful and vastly more complex antibiotics from nature: penicillin, streptomycin, tetracycline, and erythromycin, among others. These primary defences are now significantly less effective as an unavoidable consequence of rapid evolution of resistance within pathogenic bacteria, made worse by widespread misuse of antibiotics. For decades medicinal chemists replenished the arsenal of antibiotics by semisynthetic and to a lesser degree fully synthetic routes, but economic factors have led to a subsidence of this effort, which places society on the precipice of a disaster. We believe that the strategic application of modern chemical synthesis to antibacterial drug discovery must play a critical role if a crisis of global proportions is to be averted.

Deep eutectic solvents (such as the combination of either urea or glycerol with choline chloride) are effective solvents/organocatalysts for Pictet–Spengler condensations to form carbolines. The reaction conditions are quite mild and do not require additional Bronsted or Lewis acid catalyst. Given the inexpensive, non-toxic, and recyclable nature of the DES, these reaction conditions are simple and highly environmentally friendly.

A synthesis of both the natural and unnatural enantiomers of frondosin B (I) and the natural enantiomer of frondosin A (II) is developed.

A new medium-pore aluminophosphate molecular sieve, [Al72P72O288] (PST-6), is synthesized from a mixture of NHEt2, Al2O3, P2O5 and H2O (2:1:1:40; autoclave, 200 °C, 5 d) followed by calcination under flowing air at 550 °C for 8 h.

While forming any medium-sized ring requires an approach capable of overcoming significant entropic and enthalpic penalties,[1] the challenge in meeting that requirement is often more pronounced in systems composed only of carbon atoms, such as the 9-membered rings of caraphenol A (1)[2] and α-viniferin (2),[3] two oligomeric forms of the natural product resveratrol (3)[4,5] which are bioactive (including acetylcholinesterase inhibition, anti-inflammatory properties, and potential value as probes for elucidating key pathways in Alzheimer’s disease and drug resistance in tumors).[6] Indeed, without the more obvious and established array of productive cyclization strategies afforded by heteroatoms, only a handful of approaches have proven capable of accessing fully carbocyclic variants. For 9-membered rings, that includes Grob fragmentations (such as 4→5),[7] highly context specific C–C bond constructions such as the acetylide addition leading to enediyne 6,[8] and ring-closing olefin metathesis (not shown).[9] Given this landscape, as well as the unique and sp2-rich patterning of 1 and 2 (and 11 other related molecules)[10] that effectively precludes the application of these three established strategies, we sought to identify additional approaches capable of forging strained, 9-membered carbocycles. Herein, we show that a variety of Friedel–Crafts-type reactions promoted by either Au(III) or Br∅nsted acids are competent in this regard with functionally rich substrates. In addition to providing what we believe is the first example of a 9-exo-dig ring closure, late-stage application of one of the developed approaches has enabled the completion of an efficient and highly scalable total synthesis of caraphenol A (1).

Review: syntheses, spectroscopic properties, structures and reactions of fused-ring meallabenzenes; 38 refs.

Discovery, optimization, and early development of drug candidates are very challenging and require a versatile synthetic chemistry toolbox. Organozinc chemistry is a powerful methodology for carbon–carbon bond formation which tolerates several functional groups that are critical for maintaining good physicochemical properties of drug molecules. Here we demonstrate that organozinc chemistry offers facile solutions to otherwise challenging medicinal chemistry problems commonly encountered during lead optimization. In this review, we summarize several examples in which utilization of organozinc-mediated couplings enabled us to rapidly explore a medicinal chemistry hypothesis using readily available intermediates. This chemistry allowed us to make rapid decisions with limited chemistry resources. 1 Introduction 2.1 Alpha4 Integrin Antagonists 2.2 CRTH2 Antagonists 2.3 Glucokinase (GK) Activators 2.4 Leukotriene B4 (LTB4) Receptor Antagonists 2.5 Janus Activated Kinase 3 (JAK3) Inhibitors 2.6 Synthesis of Novel Scaffolds 3 Conclusions 4 Experimental Methods

Nitrocyclopropanation of amino-acid derived enones has led to a series of cyclopropyl peptidomimetics suitable for further elaboration to compounds with the potential for biological activity.

A mild and generally applicable two-step synthesis of aryl- and heteroaryl-substituted β-ketoesters via Mizoroki—Heck reaction and subsequent hydrolysis is presented.

A series of dichlorocyclophosphazanes [{ClP(μ-NR)}2 ] containing chiral and achiral R groups was obtained from simple commercially available amines and PCl3 . Their condensation reactions with axially chiral biaryl diols yielded ansa-bridged chiral cyclophosphazane (CycloP) ligands. This highly modular methodology allows extensive elaboration of the ligand set, in which the chirality can be introduced at the diol bridge and/or the amido R group. This provides the possibility to observe match and mismatch effects in catalysis. A series of twenty CycloP ligands was synthesized and characterized by multinuclear NMR spectroscopy, HRMS, elemental analysis, and in selected cases, single-crystal X-ray diffraction. These studies show that all of the ditopic CycloP ligands are C2 symmetric, rendering their metal coordination sites symmetry equivalent. Two well-established enantioselective reactions were explored by using late-transition metal CycloP complexes as catalysts; the gold-catalyzed hydroamination of γ-allenyl sulfonamides and the asymmetric nickel-catalyzed three-component coupling of a diene and an aldehyde. The steric demands of the CycloP ligands have a subtle influence on the reactivity and selectivity observed in both reactions. Good enantiomeric ratios (e.r.) as high as 89:11 in the gold-catalyzed reaction and 92:8 in the nickel-catalyzed bis-homoallylation reaction were observed.

A carefully designed process for the scalable synthesis of 1-methylcyclopropanol (III) is developed as well as the optimized conversion to the mixed carbonate (V).

A radical lipidation: Application of a novel thiol-ene lipidation enables the one-step synthesis of self-adjuvanting antigenic peptides as vaccine candidates. The resultant monoacyl lipopeptides are shown to activate monocytes in a robust manner.

Asymmetric γ-hydroxy nitriles are valuable intermediates because hydrolysis of the nitriles can result in an intramolecular cyclization to chiral γ-lactones, which have a variety of biological uses. Starting with an assortment of different aldehydes (alkyl and aryl) a 4-step synthesis of γ-keto nitriles was developed. These prochiral substrates were then screened against a library of ketoreductases for their ability to stereoselectively reduce the carbonyl. Enzymes from the short chain dehydrogenase family showed activity and these enzymatic reactions were scaled up to produce a diverse set of chiral γ-lactones.