Enantioselective lactonization catalyzed by chiral N-heterocyclic carbenes enables access to inherently chiral eight-membered lactones.

Chiral saddle-shaped molecules are an emerging class of compounds with significant potential in both materials science and medicinal chemistry. However, their broader application has been hindered by limited synthetic accessibility. Herein, we report a metal-free, organocatalytic protocol for the oxidative lactonization of readily available aldehydic derivatives, enabling the efficient synthesis of chiral saddle-shaped lactones.

The Khamkhains, Neurotrophic Drimane-Type Sesquiterpenoids Derived from a Polyporaceous Basidiomycete Originating from Thailand.

Eight unprecedented terpenoids were isolated from submerged cultures of a polyporoid basidiomycete originating from Thailand (which had been referred to as " sp." in a previous publication) by preparative chromatography. Their chemical structures were elucidated by extensive two-dimensional nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry.

Enantioselective Pictet-Spengler-Type Reaction via a Helically Chiral Anion as an Access to 4,5-Dihydropyrrolo[1,2-]quinoxaline Scaffolds.

We report an enantioselective Pictet-Spengler-type reaction enabled by a cost-effective and readily available helically chiral cyclopentadiene (PCCP) catalyst. This methodology, conducted under mild reaction conditions, facilitates the synthesis of a novel class of chiral 4,5-dihydropyrrolo[1,2-]quinoxalines (DHPQs) characterized by enhanced resistance to aromatization due to intramolecular hydrogen bonding. Additionally, the protocol exhibits broad substrate compatibility and demonstrates significant synthetic versatility.

Surface inclusion and dynamics of cucurbit[7]uril-based supramolecular complexes.

A supramolecular complex acting as a molecular rotor was assembled from cucurbit[7]uril and a rigid, rod-shaped molecular anchor. This rotor was then anchored to the facets of a hexagonal tris(-phenylenedioxy)cyclotriphosphazene matrix, forming a regular 2D array. Semi-empirical calculations revealed very low rotational barriers for the macrocyclic units within this array, suggesting smooth rotational motion and promising potential for future applications in dynamic molecular systems.

Gunacins: Novel Benzo[]chromene Derivatives from the Fungus Exobasidium sp. and Their Potent Anti-Leishmania and Trypanosoma Activities.

Six new pyranonaphthoquinone derivatives, gunacin A-E (), along with the known compounds gunacin () and the isocoumarin derivative (+) orthosporin (), were isolated from the fungus Exobasidium sp. Their chemical structures were elucidated by X-ray crystallography, extensive spectroscopic analysis supported by ROESY experiments, and mass spectrometry. Two tested compounds (, ) demonstrated high activity against Leishmania mexicana and four salivarian Trypanosoma species, with the lowest detected EC value of 0.

Extraordinary kinetic inertness of lanthanide(iii) complexes of pyridine-rigidified 18-membered hexaazamacrocycles with four acetate pendant arms.

Large polyazamacrocycles are used for the complexation of large metal ions. However, their coordination chemistry has not been frequently studied until now. An eighteen-membered macrocycle with two rigidifying pyridine rings and four aliphatic amino groups substituted with four acetic acid pendants, Hpyta, provides a large ligand cavity and coordination number (CN) up to 10.

Desymmetric esterification catalysed by bifunctional chiral N-heterocyclic carbenes provides access to inherently chiral calix[4]arenes.

Calix[4]arenes display inherent chirality, with broad applications in synthetic and medicinal chemistry and in materials sciences. However, their use is hindered by their limited synthetic accessibility, primarily due to the lack of enantioselective methods for preparing chiral calix[4]arenes with an ABCC substitution pattern. Here, we address this challenge by presenting a simple, efficient, and metal-free protocol for organocatalytic desymmetrisation of prochiral diformylcalix[4]arenes.

Changing the properties of monodentate and P,C-chelating ferrocenyl-substituted 1,2,3-triazol-5-ylidene ligands through an inserted carbonyl moiety.

Triazolylidenes derived from readily accessible triazoles are useful ligands for coordination chemistry and catalysis. This work describes the synthesis of Group 11 metal complexes of new ferrocenyl-substituted triazolylidene ligands in which the ferrocene and triazolylidene moieties are separated by a carbonyl linker. In particular, complexes of types [MCl(FcC(O){CN(Mes)NN(Me)}-κ)] (M = Cu or Au; Fc = ferrocenyl) and [M(FcC(O){CN(Mes)NN(Me)}-κ)][BF] (M = Cu, Ag, or Au) were prepared from FcC(O)CCH and characterised by spectroscopic methods, X-ray diffraction analysis and cyclic voltammetry.

Enantioselective Synthesis of Spirocyclic Isoxazolones Using a Conia-Ene Type Reaction.

Stereoselective synthesis of spirocyclic compounds containing heterocyclic motifs represents a formidable challenge in enantioselective synthesis. Here, we present a cascade reaction between α,β-unsaturated aldehydes and isoxazolones under synergistic catalysis of a chiral secondary amine and a palladium(0) catalyst. This strategy allows access to chiral spiroisoxazolone derivatives with a large substrate scope tolerance and high levels of diastereoselectivity (dr up to 20:1) and enantioselectivity (up to 99% ee).

P NMR Study of P-Chirogenic Phosphaphenanthrenes with Molecular Flexibility tuned by Amino Acid Substituents.

Model phosphonamidates derived from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) with molecular flexibility tuned by amino acid substituents were prepared as pairs of diastereoisomers (DSIs) differing in configuration on phosphorus atom. X-ray diffraction (XRD) determined absolute configuration on phosphorus and revealed conformational flexibility of six-membered oxa-phospha-cycle. Quantum-chemical calculations combined with machine learning provided 2-4 representative conformers from each DSI present in solution.

C-H amination of enolizable and nonenolizable ketones.

We present a method for the amination of enolizable and non-enolizable ketones in the alpha (or beta) position to the carbonyl group. This approach is based on the conversion of the corresponding cyanohydrins to carbonazidates, precursors for thermal intramolecular nitrene insertion reactions into the adjacent C-H bond. Hydrolysis of the resulting carbamates under basic conditions with simultaneous regeneration of the carbonyl group yields amino ketones.

Lanthanide Oxalates: From Single Crystals to 2D Functional Honeycomb Nanosheets.

Oxalates are simple, low-cost but crucial compounds in the technology of lanthanides, actinides, and transition metals. Apart from using oxalate as a versatile ligand in coordination chemistry, simple oxalate salts are still under a scientific focus, linked with ion batteries, optical and magnetic materials, and, most importantly, industrial-technological mining and separation loops. The typically low solubility of oxalate salts is advantageous from the viewpoint of a convenient and affordable synthesis requiring only green solvents.

Synthesis of highly fluorescent helical quinolizinium salts by a Rh-catalyzed cyclotrimerization/C-H activation sequence.

A series of helical quinolizinium salts were prepared utilizing Rh-catalyzed [2+2+2]cyclotrimerization and C-H activation processes as the crucial synthetic steps. The cyclotrimerization of appropriately substituted diynes with trimethylsilylethyne under Rh-catalyzed conditions provided the 1-arylisoquinolines in up to 61% isolated yields. Their Rh-catalyzed C-H activation/annulation with various aryl and alkyl disubstituted alkynes gave rise to [7]-helical quinolizinium salts in high isolated yields (up to 93%).

Pd-catalysed C-H bond functionalisation route to 1,2-dihydroferroceno[]isoquinoline and its annellated derivatives and the reactivity of these compounds.

C-H bond functionalisation has developed into a powerful synthetic methodology that is applicable to a wide array of substrates, including organometallic compounds. In this study, racemic, planar-chiral 1,2-dihydroferroceno[]isoquinoline and analogous helical compounds with one or two additional -fused benzene rings were synthesised by palladium-catalysed C-H bond activation/cyclisation of -[(bromoaryl)methyl]--(methylsulfonyl)aminoferrocenes. These starting materials are readily accessible from FcNHSOMe (Fc = ferrocenyl) and appropriate vicinal bromo-(bromomethyl)arenes.

Enantioselective Preparation of Cyclopentene-Based Amino Acids with a Quaternary Carbon Center.

Azlactone is an important starting material for synthesizing amino acids containing a quaternary α-carbon. In this study, we have developed a sequential "one-pot" procedure involving an enantioselective spirocyclization reaction followed by acidic azlactone opening, which led to amino acid derivatives. The key step of this procedure is a spirocyclization between propargylated azlactones and enals by using a cooperative catalytic approach that combines chiral secondary amine and achiral Pd(0) complexes.

Synthesis and structural confirmation of selaginpulvilin X.

We report the first total synthesis of the natural product selaginpulvilin X, a selaginellaceae polyphenol class of compounds. Our synthetic strategy employs cross-coupling reactions and an organolithium addition to construct the carbon framework. Subsequently, the functional group modifications and deprotection yield the natural product.

Triptycene-Based Tripodal Molecular Platforms.

Molecular platforms are essential components of various surface-mounted molecular devices. Here, we document the synthesis of two universal triptycene-based tripodal pedestals featuring terminal alkynes in the axial position. We showcase their versatility by incorporating them into the structures of diverse functional molecules such as unidirectional light-driven molecular motors, photoswitches, and Brownian molecular rotors using standard cross-coupling reactions.

Influence of Selective Deoxyfluorination on the Molecular Structure of Type-2 -Acetyllactosamine.

-Acetyllactosamine is a common saccharide motif found in various biologically active glycans. This motif usually works as a backbone for additional modifications and thus significantly influences glycan conformational behavior and biological activity. In this work, we have investigated the type-2 -acetyllactosamine scaffold using the complete series of its monodeoxyfluorinated analogs.

Regio- and Enantioselective -Heterocyclic Carbene-Catalyzed Annulation of Aminoindoles Initiated by Friedel-Crafts Alkylation.

Chiral indoles annulated on the benzene ring are unique and significant in natural and medicinal compounds. However, accessing these enantioenriched molecules has often been overlooked. The present study introduces an organocatalytic protocol to access these compounds efficiently, demonstrated by substrate scope, functional group tolerance, and using only 1 mol % of a chiral conjugated acid catalyst.

Complex isomerism influencing the textural properties of organometallic [Cu(salen)] porous polymers: paramagnetic solid-state NMR characterization and heterogeneous catalysis.

Although organometallic porous polymer networks are recognized as promising heterogeneous catalysts, the relationship between ligand/monomer geometry and network parameters is usually not well understood due to the lack of atom-resolved characterization methods for the amorphous network matrix. In this work, a series of copper(II) salen-type metal complexes was synthesized, using - and -1,2-diaminocyclohexane segments, and thoroughly characterized by single-crystal X-ray diffraction and solution- and solid-state NMR spectroscopy. Terminal ethynyl groups of the complexes were then transformed into polyacetylene chains by coordination chain-growth homopolymerization, resulting in highly porous (458-655 m g) organometallic polymer networks with a copper(II) ion content of about 12 wt%.

Resolution of 9,10-Diketo[7]helicene and Its Use in One-Step Preparation of Helicene-Based D-A-D Push-Pull Systems.

Racemic 9,10-diketo[7]helicene was successfully separated into enantiomers using a reversible and stereoselective reaction with 2,2'-diamino-1,1'-binaphthalene with moderate yields but with remarkable purity (>99% de). The enantiomerically pure diketone was used as a convenient starting material for the preparation of helicene-based push-pull molecules, which incorporated aza-aryl acceptors and diarylaminophenylene donor groups in a single step. A series of six push-pull systems, along with three reference molecules without donors, were prepared and studied using UV/vis and fluorescence measurements, circular dichroism, and DFT calculations.

Foldamers controlled by functional triamino acids: structural investigation of α/γ-hybrid oligopeptides.

Peptide-like foldamers controlled by normal amide backbone hydrogen bonding have been extensively studied, and their folding patterns largely rely on configurational and conformational constraints induced by the steric properties of backbone substituents at appropriate positions. In contrast, opportunities to influence peptide secondary structure by functional groups forming individual hydrogen bond networks have not received much attention. Here, peptide-like foldamers consisting of alternating α,β,γ-triamino acids 3-amino-4-(aminomethyl)-2-methylpyrrolidine-3-carboxylate (AAMP) and natural amino acids glycine and alanine are reported, which were obtained by solution phase peptide synthesis.

Synthesis and catalytic properties of palladium(II) complexes with P,π-chelating ferrocene phosphinoallyl ligands and their non-tethered analogues.

Hybrid phosphines usually combine a phosphine moiety with another heteroatom secondary donor group in their structures while compounds equipped with hydrocarbyl π-donor moieties remain uncommon. This contribution reports the synthesis and structural characterization of the first P/π-allyl-chelating complexes that were obtained using the structurally flexible and redox-active ferrocene unit as the scaffold, . [PdCl(RPfcCHCHCH-η:κ)] (1R; R = Ph and cyclohexyl (Cy); fc = ferrocene-1,1'-diyl).

Organocatalytic desymmetrization provides access to planar chiral [2.2]paracyclophanes.

Planar chiral [2.2]paracyclophanes consist of two functionalized benzene rings connected by two ethylene bridges. These organic compounds have a wide range of applications in asymmetric synthesis, as both ligands and catalysts, and in materials science, as polymers, energy materials and dyes.

Transition metal complexes of the (2,2,2-trifluoroethyl)phosphinate NOTA analogue as potential contrast agents for F magnetic resonance imaging.

A new hexadentate 1,4,7-triazacyclononane-based ligand bearing three coordinating methylene-(2,2,2-trifluoroethyl)phosphinate pendant arms was synthesized and its coordination behaviour towards selected divalent (Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn) and trivalent (Cr, Fe, Co) transition metal ions was studied. The ligand forms stable complexes with late divalent transition metal ions (from Co to Zn) and the complexes of these metal ions are formed above pH ∼3. A number of complexes with divalent metal ions were structurally characterized by means of single-crystal X-ray diffraction.