Insight into the Structure of Antifungal Cyrmenins: Conformational Studies of Unique Dehydroamino Acid, O-Methyldehydroserine.

O-Methyldehydroserine, ΔSer(Me), is a non-standard α,β-dehydroamino acid, which occurs naturally in Cyrmenins with potential pharmaceutical application. The C-terminal part and the side chain of the ΔSer(Me) residue constitute the β-methoxyacrylate unit, responsible for antifungal activity of Cyrmenins. The short model, Ac-ΔSer(Me)-OMe, was analyzed considering the geometrical isomer Z () and E ().

Ferroelectric, Switchable Dielectric and Nonlinear Optical Properties in Inorganic-Organic Lead-Free 1D Hybrids Based on Bi(III) and Azetidine: (CNH)[BiCl], (CNH)[BiBr].

This study investigates lead-free organic-inorganic hybrids (CNH)[BiCl] () and (CNH)[BiBr] (), focusing on their structural, dielectric, ferroelectric, and optical properties. Both compounds exhibit paraelectric () to ferroelectric () phase transitions (PTs) at 230/233 K and 228/229 K, respectively, transitioning from orthorhombic () to monoclinic (2) phases, with distorted [BiX] octahedra forming 1D chains. Quasielastic neutron scattering and solid-state H NMR studies reveal the localized motion of azetidinium cations.

Stereoselective mechanochemical synthesis of thiomalonate Michael adducts via iminium catalysis by chiral primary amines.

The study presents a novel approach utilizing iminium salt activation and mild enolization of thioesters, offering an efficient and rapid synthesis of Michael adducts with promising stereoselectivity and marking a significant advancement in mechanocatalysis. The stereoselective addition of bisthiomalonates - to cyclic enones and 4-chlorobenzylideneacetone proceeds stereoselectively under iminium activation conditions secured by chiral primary amines, in contrast to oxo-esters as observed in dibenzyl malonate addition. Mild enolization of thioesters allows for the generation of Michael adducts with good yields and stereoselectivities.

IPr* - wingtip-flexible, sterically hindered, modular, N,C/S,C-chelating thiazole-donor N-heterocyclic carbene ligands.

N-Heterocyclic carbenes (NHCs) represent a pivotal class of ligands in coordination chemistry owing to their unique electronic properties. In particular, hemilabile N-heterocyclic carbenes have garnered significant attention over the past decade due to their capacity to transiently coordinate to metals and open coordination sites. However, hemilabile NHC ligands have been predominantly limited to N, O and P donors, while NHC ligands bearing versatile S-donors have been severely underdeveloped.

Titanium and Vanadium Complexes of Tridentate Phenoxy-Imine and Phenoxy-Amine Ligands and Their Application in the Ring-Opening Polymerization of Cyclic Esters.

Phenoxy-imine and phenoxy-amine proligands, with the additional OH donor groups 2,4-Bu-6-(2-CH(OH)-CHN=CH)CHOH (), 6-(2-CH(OH)-CHN=CH)CHOH (), and 2,4-Bu-6-(2-CH(OH)-CHNH-CH)CHOH (), were synthesized and their titanium (-) and vanadium (-) complexes were prepared in reactions with Ti(OPr) and VO(OPr), respectively. All new compounds were characterized with the use of FTIR, H, and C NMR spectroscopy; X-ray crystallography was also used to study proligands. All the complexes proved to be active catalysts in the ring-opening polymerization (ROP) of -caprolactone, -lactide, and -lactide in the melt.

Well-Defined, Air- and Moisture-Stable Palladium-Imidazo[1,5-]pyridin-3-ylidene Complexes: A Versatile Catalyst Platform for Cross-Coupling Reactions by L-Shaped NHC Ligands.

We describe the development of [(NHC)Pd(cinnamyl)Cl] complexes of ImPy (ImPy = imidazo[1,5-]pyridin-3-ylidene) as a versatile class of precatalysts for cross-coupling reactions. These precatalysts feature fast activation to monoligated Pd(0) with 1:1 Pd to ligand ratio in a rigid imidazo[1,5-]pyridin-3-ylidene template. Steric matching of the C5-substituent and N2-wingtip in the catalytic pocket of the catalyst framework led to the discovery of ImPyMesDipp as a highly reactive imidazo[1,5-]pyridin-3-ylidene ligand for Pd-catalyzed cross-coupling of nitroarenes by challenging C-NO activation.

IPr* - a new class of sterically-hindered, wingtip-flexible N,C-chelating oxazole-donor N-heterocyclic carbene ligands.

N-heterocyclic carbenes (NHCs) have emerged as a major direction in ancillary ligand development for stabilization of reactive metal centers in inorganic and organometallic chemistry. In particular, wingtip-flexible NHCs have attracted significant attention due to their unique ability to provide a sterically-demanding environment for transition metals in various oxidation states. Herein, we report a new class of sterically-hindered, wingtip-flexible NHC ligands that feature N,C-chelating oxazole donors.

Insight into the Structure of Victorin, the Host-Selective Toxin from the Oat Pathogen . Studies of the Unique Dehydroamino Acid β-Chlorodehydroalanine.

Victorins, a family of peptide toxins, produced by the fungal pathogen and responsible for disease of some oat varieties, contain a β-chlorodehydroalanine residue, ΔAla(βCl). To determine the conformational properties of this unique dehydroamino acid, a series of model compounds was studied using X-ray, NMR, and FT-IR methods, supported by theoretical calculations. The ΔAla(βCl) geometrical isomers differ in conformational profile.

IOct (IOctyl) - pushing the limits of IBu: highly hindered electron-rich N-aliphatic N-heterocyclic carbenes.

IBu (IBu = 1,3-di--butylimidazol-2-ylidene) represents the most important and most versatile -alkyl N-heterocyclic carbene available in organic synthesis and catalysis. Herein, we report the synthesis, structural characterization and catalytic activity of IOct (IOctyl), -symmetric, higher homologues of IBu. The new ligand class, including saturated imidazolin-2-ylidene analogues has been commercialized in collaboration with MilliporeSigma: IOct, 929 298; SIOct, 929 492 to enable broad access of the academic and industrial researchers within the field of organic and inorganic synthesis.

One-Pot Phosphonylation of Heteroaromatic Lithium Reagents: The Scope and Limitations of Its Use for the Synthesis of Heteroaromatic Phosphonates.

A one-pot lithiation-phosphonylation procedure was elaborated as a method to prepare heteroaromatic phosphonic acids. It relied on the direct lithiation of heteroaromatics followed by phosphonylation with diethyl chlorophosphite and then oxidation with hydrogen peroxide. This protocol provided the desired phosphonates with satisfactory yields.

Bony Canal Method of Dexamethasone Injections in Aggressive Form of Central Giant Cell Granuloma-Case Series.

Central Giant Cell Granuloma constitutes approximately 7% of benign tumors of the jaws. The aggressive form of CGCG clinically behaves like a classic semi-malignant neoplasm. In the literature, the suggested method of treatment of aggressive forms of CGCG is curettage or resection with the margin of 0.

L-Shaped Heterobidentate Imidazo[1,5-a]pyridin-3-ylidene (N,C)-Ligands for Oxidant-Free Au /Au Catalysis.

In the last decade, major advances have been made in homogeneous gold catalysis. However, Au /Au catalytic cycle remains much less explored due to the reluctance of Au to undergo oxidative addition and the stability of the Au intermediate. Herein, we report activation of aryl halides at gold(I) enabled by NHC (NHC=N-heterocyclic carbene) ligands through the development of a new class of L-shaped heterobidentate ImPy (ImPy=imidazo[1,5-a]pyridin-3-ylidene) N,C ligands that feature hemilabile character of the amino group in combination with strong σ-donation of the carbene center in a rigid conformation, imposed by the ligand architecture.

CAAC-IPr*: easily accessible, highly sterically-hindered cyclic (alkyl)(amino)carbenes.

IPr* (IPr* = 1,3-bis(2,6-bis(diphenylmethyl)-4-methylphenyl)imidazol-2-ylidene) has emerged as a powerful highly hindered and sterically-flexible ligand platform for transition-metal catalysis. CAACs (CAAC = cyclic (al-kyl)(amino)carbenes) have gained major attention as strongly electron-rich carbon analogues of NHCs (NHC = N-heterocyclic carbene) with broad applications in both industry and academia. Herein, we report a merger of CAAC ligands with highly-hindered IPr*.

N-Heterocyclic Carbene Complexes of Nickel(II) from Caffeine and Theophylline: Sustainable Alternative to Imidazol-2-ylidenes.

Xanthines, such as caffeine and theophylline, are abundant natural products that are often present in foods. Leveraging renewable and benign resources for ligand design in organometallic chemistry and catalysis is one of the major missions of green and sustainable chemistry. In this Special Issue on , we report the first nickel-N-heterocyclic carbene complexes derived from Xanthines.

Pd-PEPPSI N-Heterocyclic Carbene Complexes from Caffeine: Application in Suzuki, Heck, and Sonogashira Reactions.

The first synthesis of Pd-PEPPSI N-heterocyclic carbene complexes derived from the abundant and renewable natural product caffeine is reported. The catalysts bearing 3-chloro-pyridine, pyridine and N-methylimidazole ancillary ligands were readily prepared from the corresponding N9-Me caffeine imidazolium salt by direct deprotonation and coordination to PdX in the presence of N-heterocycles or by ligand displacement of PdX(Het). The model Pd-PEPPSI-caffeine complex has been characterized by x-ray crystallography.

Synthesis of Tetrapeptides Containing Dehydroalanine, Dehydrophenylalanine and Oxazole as Building Blocks for Construction of Foldamers and Bioinspired Catalysts.

The incorporation of dehydroamino acid or fragments of oxazole into peptide chain is accompanied by a distorted three-dimensional structure and additionally enables the introduction of non-typical side-chain substituents. Thus, such compounds could be building blocks for obtaining novel foldamers and/or artificial enzymes (artzymes). In this paper, effective synthetic procedures leading to such building blocks-tetrapeptides containing glycyldehydroalanine, glycyldehydrophenylalanine, and glycyloxazole subunits-are described.

Crosstalk between Statins and Cancer Prevention and Therapy: An Update.

The importance of statins in cancer has been discussed in many studies. They are known for their anticancer properties against solid tumors of the liver or lung, as well as diffuse cancers, such as multiple myeloma or leukemia. Currently, the most commonly used statins are simvastatin, rosuvastatin and atorvastatin.

Effect of conjugated system extension on structural features and electron-density distribution in charge-transfer difluoroborates.

A comparative structural study of two related donor-acceptor pyridine-based BF complexes, namely, 3-(dimethylamino)-1,1-difluoro-1H-pyrido[1,2-c][1,3,5,2]oxadiazaborinin-9-ium-1-uide, CHBFNO (1), and 3-{(1E,3E)-4-[4-(dimethylamino)phenyl]buta-1,3-dien-1-yl}-1,1-difluoro-1H-pyrido[1,2-c][1,3,5,2]oxadiazaborinin-9-ium-1-uide, CHBFNO (2), containing a dimethylamino group and either the shortest (in 1) or the longest (in 2) charge-transfer path known until now in this family of compounds, is presented. Single-crystal X-ray diffraction analysis supported by computational investigations shed more light on these systems, indicating, among other aspects, the predominance of C-H..

Evaluation of Cyclic Amides as Activating Groups in N-C Bond Cross-Coupling: Discovery of -Acyl-δ-valerolactams as Effective Twisted Amide Precursors for Cross-Coupling Reactions.

The development of efficient methods for facilitating N-C(O) bond activation in amides is an important objective in organic synthesis that permits the manipulation of the traditionally unreactive amide bonds. Herein, we report a comparative evaluation of a series of cyclic amides as activating groups in amide N-C(O) bond cross-coupling. Evaluation of -acyl-imides, -acyl-lactams, and -acyl-oxazolidinones bearing five- and six-membered rings using Pd(II)-NHC and Pd-phosphine systems reveals the relative reactivity order of N-activating groups in Suzuki-Miyaura cross-coupling.

Synthesis and Inhibitory Studies of Phosphonic Acid Analogues of Homophenylalanine and Phenylalanine towards Alanyl Aminopeptidases.

A library of novel phosphonic acid analogues of homophenylalanine and phenylalanine, containing fluorine and bromine atoms in the phenyl ring, have been synthesized. Their inhibitory properties against two important alanine aminopeptidases, of human (hAPN, CD13) and porcine (pAPN) origin, were evaluated. Enzymatic studies and comparison with literature data indicated the higher inhibitory potential of the homophenylalanine over phenylalanine derivatives towards both enzymes.

A novel approach for obtaining α,β-diaminophosphonates bearing structurally diverse side chains and their interactions with transition metal ions studied by ITC.

Aminophosphonates are an important group of building blocks in medicinal and pharmaceutical chemistry. Novel representatives of this class of compounds containing nontypical side chains are still needed. The aza-Michael-type addition of amines to phosphonodehydroalanine derivatives provides a simple and effective approach for synthesizing '-substituted α,β-diaminoethylphosphonates and thus affords general access to aminophosphonates bearing structurally diverse side chains.

Phosphonic Acid Analogs of Fluorophenylalanines as Inhibitors of Human and Porcine Aminopeptidases N: Validation of the Importance of the Substitution of the Aromatic Ring.

A library of phosphonic acid analogs of phenylalanine substituted with fluorine, chlorine and trifluoromethyl moieties on the aromatic ring was synthesized and evaluated for inhibitory activity against human (hAPN) and porcine (pAPN) aminopeptidases. Fluorogenic screening indicated that these analogs are micromolar or submicromolar inhibitors, both enzymes being more active against hAPN. In order to better understand the mode of the action of the most active compounds, molecular modeling was used.

-Acyl-glutarimides: Effect of Glutarimide Ring on the Structures of Fully Perpendicular Twisted Amides and N-C Bond Cross-Coupling.

-Acyl-glutarimides have emerged as the most reactive precursors for N-C(O) bond cross-coupling reactions to date, wherein the reactivity is driven by ground-state destabilization of the amide bond. Herein, we report a full study on the effect of a glutarimide ring on the structures, electronic properties, and reactivity of fully perpendicular -acyl-glutarimide amides. Most notably, this report demonstrates the generality of deploying -acyl-glutarimides to achieve full twist of the acyclic amide bond, and results in the discovery of -acyl-glutarimide amide with an almost perfect twist value, τ = 89.

Structural phase transitions coupled with prominent dielectric anomalies and dielectric relaxation in [(CH)NH][KCo(CN)] and mixed [(CH)NH][KFeCo(CN)] double perovskite hybrids.

The crystals of pure [(CH)NH][KFe(CN)] (TrMAFe) and [(CH)NH][KCo(CN)] (TrMACo) as well as their mixed crystals (TrMAFeCo), with different ratios of x = 0, 0.12, 0.18, 0.

Reactions of Piperazin-2-one, Morpholin-3-one, and Thiomorpholin-3-one with Triethyl Phosphite Prompted by Phosphoryl Chloride: Scope and Limitations.

The reaction of the title lactams with triethyl phosphite prompted by phosphoryl chloride provided six-membered ring heterocyclic phosphonates or bisphosphonates. These novel scaffolds might be of interest as building blocks in medicinal chemistry. The course of the reaction was dependent on the structure of the used substrate.