Benzyl Group Research Articles

Direct Synthesis of Benzhydryl-Functionalized 3,4-Dihydropyridin-2-ones from 2-Pyridones and Their Use in the Formation of Bridged δ-Lactams

A method for the synthesis of C4-benzhydryl-functionalized 3,4-dihydropyridin-2-ones using complementary addition of benzhydryllithium and/or benzhydrylmagnesiate reagents to 2-pyridones, with high regioselectivity triggered by substituents, is described. A partially stereoselective cyclization was successfully demonstrated using TfOH and/or TIPSOTf as Brønsted and Lewis acids, respectively, leading to C6-phenyl-functionalized 7,8-benzomorphanones. It is also shown that the use of functionalized δ-enelactams obtained with an active methoxy-substituted benzyl group at C3 enabled the preparation of a new C3–C6 bridged system within the δ-lactam framework.

Enhancing stability of cationic palladium complexes with hemilabile 2-benzyl oxazoline ligands: Structural insights and catalytic implications

This article describes the synthesis and characterization of Pd cationic complexes incorporating mono(2-benzyl oxazoline) ligands. Our study focuses on exploring the impact of electrostatic interactions of aromatic π-electrons of the benzyl group, aimed at enhancing the structural rigidity of cationic Pd complexes. Introduction of an aromatic moiety, which weakly coordinates with the Pd cation, led to a two-fold increase in the stability of the Pd cationic complex compared to complexes lacking any coordinating substituents. This research represents the initial instance of a cationic Pd complex with 2-benzyl oxazolines, highlighting the importance of weak electrostatic interactions in elucidating the three-dimensional structure of a metal complex.

Synthetic studies on fusicoccin A: Enantioselective synthesis of the C-ring fragment

The enantioselective synthesis of the C-ring fragment of fusicoccin A is described. The TBS ether of hydroxyketone prepared by baker’s yeast reduction was converted to the α-ethylidene ketone by aldol condensation with propionaldehyde, followed by Michael reaction with divinylcopper reagent and conversion to enol triflate to afford a single diastereomer. X-ray crystallographic analysis of the crystalline derivative of the single diastereomer showed that the asymmetric carbon formed by the Michael reaction was consistent with the configuration of the C15 asymmetric carbon of fusicoccin A. The vinyl group of the enol triflate was converted to a hydroxymethyl group by selective dihydroxylation with a bulky ligand, oxidative cleavage of the resultant 1,2-diol with lead tetraacetate, and DIBAL-H reduction. The hydroxymethyl group was subsequently converted to TBS ether, followed by the hydrogenolysis of the benzyl group and Dess–Martin oxidation, accomplishing the enantioselective synthesis of the desired C-ring fragment of fusicoccin A.

CuI/CuII Chiral Homoleptic Complexes: Study of Self‐Recognition and Self‐Discrimination

AbstractThe formation of ML2 homoleptic copper(I) and copper(II) complexes from bidentate chiral ligands with C2 symmetry, comprising three types of substituents (namely benzyl, indanyl and phenyl groups), was investigated. The formation of homochiral or heterochiral complexes can be influenced by the nature of the substituents and the geometry induced by the oxidation state of the metal. All the complexes were isolated and characterized, in particular in the solid state by X‐ray diffraction studies. In solution, cyclic voltammetry was used to study ligand association and discrimination induced by the CuI/CuII transition.

Skeletal Editing of Mechanically Interlocked Molecules: Nitrogen Atom Deletion from Crown Ether-Dibenzylammonium Rotaxanes.

Removing the nitrogen atom from secondary amines while simultaneously linking the remaining fragments is a powerful form of late-stage skeletal editing. Here, we report its use for the deletion of the nitrogen atom of the dibenzylammonium template used to assemble crown ether rotaxanes. The reaction uses an anomeric amide that activates secondary amines to generate a carbon-carbon bond that replaces the amine nitrogen. Despite the potential for dethreading of the intermediate diradical pair, the nitrogen atom was successfully deleted from a series of rotaxane axles as long as the macrocycle could access coconformations that did not inhibit the reaction of the amine group. The skeletally edited interlocked molecules were obtained directly from the parent crown ether-dibenzylammonium rotaxanes in modest yields (23-36%) and characterized by NMR spectroscopy, mass spectrometry, and X-ray crystallography. One skeletally edited rotaxane shows a network of weak CH···O hydrogen bonds between the crown ether and benzylic methylene groups of the axle in the solid state, in place of the crown ether-ammonium binding motif used to assemble the parent, unedited, rotaxane.

Oxidative Remote Aryl Rearrangement of N-Cinnamyl-N-alkoxybenzyl Sulfonamides Using Hypervalent Iodine(III).

An oxidative remote aryl rearrangement of N-cinnamyl-N-alkoxybenzyl sulfonamides with a hypervalent iodine(III) compound was developed to furnish 5,6-disubstituted 1,3-oxazinanes in high yields. This reaction proceeded through the dearomatization of the alkoxybenzene ring on the benzyl group, which acts as a good aryl donor, inducing the regioselective installation of the aryl group and the oxygen atom via cascade transformation. An enantioselective oxidative remote aryl rearrangement using C2-symmetrical chiral iodoarene gave enantioenriched products with high enantioselectivity.

Polarity-Driven Thiyl Radical-Catalyzed Aerobic Debenzylation of Ethers and Amines.

We report the use of a strongly electrophilic thiyl radical derived from commercially available pentafluorothiophenol as a demonstration of highly chemoselective H atom abstraction from electron-rich and relatively weak benzylic C-H bonds adjacent to the O and N atoms. This approach enables the selective oxidative removal of benzyl and p-methoxybenzyl groups from amines and ethers under ambient aerobic conditions.

Alkoxy Exchange Strategy for the Synthesis of N,N'-Dimethylated (Alkoxy)triazinediones as Solid Reagents for Acid-Catalyzed O-Alkylation.

N,N'-Dimethylated (alkoxy)triazinediones (DMATs-R) with eight different O-alkyl groups (R), such as benzyl, allyl, and tert-butyl groups, were synthesized in 61-94% yield through the alkoxy exchange reaction of DMAT-Me with the corresponding alcohol. Molecular sieves were added to the reaction mixture to shift the alkoxy exchange equilibrium toward the product via the absorptive removal of the methanol formed in situ. All the DMATs-R were obtained as stable solids, in contrast to previously reported N,N'-diallyl analogs that included oil compounds. The treatment of alcohols with DMATs-R in the presence of an acid catalyst afforded the corresponding alkyl ethers in up to 92% yield. A base-labile bromoalkyl group is compatible with these reactions. The O-tert-butylation of a sterically hindered tert-alcohol with DMAT-tBu yielded the di-tert-butyl ether product. The DMATs-R are suitable reagents for the O-alkylative protection of alcohols under nonbasic conditions.

Divergent Reactivity of Iminyl Radicals in Four Interrupted Pathways for the Synthesis of Cyclic/Acyclic Ketones and N-Heterocycles from Vinyl Azides and Phenylacetic Acids.

Herein, we report the Ag-catalyzed substrate-controlled interrupted radical pathways of the iminyl radical. The benzylic groups played a crucial role in pathway selection involving a series of dimerization and hydrolysis, a 1,5-H shift followed by cascade radical cyclization, and direct N-(sp2)/aromatization reactions that provide access to diverse cyclic/acyclic ketones, quinolines, and phenanthridine derivatives. Contrary to previous reports, mechanistic investigations with high-resolution mass spectrometry analysis uncovered the involvement of rare azine, oxime, and β-functionalized vinyl azide intermediates.

Rhodium-catalyzed site-selective cross-couplings of indoles and pyridotriazoles through carbene insertion

The switchable cross-coupling of indoles and pyridotriazoles through carbene insertion at C2- or C3-positon has been developed in this paper. This highly site-selective C−H carbenoid functionalization is determined by both the Rh-catalyst species and auxiliary groups. [Cp*RhCl2]2 and coordinating pyrimidyl group direct the C−H carbenoid functionalization to occur at the C2-position, while Rh2OAc4 and non-coordinating benzyl group lead the reaction to occur at the C3-position of the indoles. This regioselective C−H functionalization strategy is of significant importance for the discovery of indole drugs.

Structural characterization of nitazene analogs using electron ionization-mass spectrometry (EI-MS)

Nitazene analogs are among the most recent and potent additions to the novel synthetic opioid (NSO) market, and new analogs continue to emerge. Seized drug analysis commonly utilizes gas chromatography-electron ionization-mass spectrometry (GC-EI-MS), so it is therefore imperative to understand how nitazene analogs behave under EI-MS conditions, and how substitution at various sites on the molecule may impact the resulting EI mass spectra. This study characterizes the EI fragmentation behavior of 20 representative nitazene analogs that contain differing substitutions and proposes rational mechanisms to explain the observed behavior.A general EI fragmentation pathway for nitazene analogs was proposed, with the most common nitazene fragment ions being observed at m/z 86, m/z 107, m/z 58, and m/z 77. Characteristic ions were determined for different substitution groups, enabling the identification of diethyl, desethyl, pyrrolidine, and piperidine substitutions at the amine moiety, and different alkoxy chain lengths at the aromatic ring of the benzyl group. Mechanisms for the formation of these characteristic ions were proposed with the aid of isotopically labeled standards and high-resolution mass spectrometry measurements. To help with the interpretation of EI mass spectra for nitazene analogs, decision trees were developed that encompass the characteristic fragment ions observed for substitutions to the amine moiety and benzyl group, with additional criteria provided for substitutions to the benzimidazole moiety. This study summarizes the fragmentation patterns and characteristic fragment ions in the EI mass spectra of 20 representative nitazene analogs, which will aid the seized drug community in identifying novel nitazene analogs.

Cytotoxic and Anti-HSV-1 Effects of Caulerpin Derivatives.

Marine organisms represent a potential source of secondary metabolites with various therapeutic properties. However, the pharmaceutical industry still needs to explore the algological resource. The species Caulerpa lamouroux Forssk presents confirmed biological activities associated with its major compound caulerpin, such as antinociceptive, spasmolytic, antiviral, antimicrobial, insecticidal, and cytotoxic. Considering that caulerpin is still limited, such as low solubility or chemical instability, it was subjected to a structural modifications test to establish which molecular regions could accept structural modification and to elucidate the cytotoxic bioactive structure in Vero cells (African green monkey kidney cells, Cercopithecus aethiops; ATCC, Manassas, VA, USA) and antiviral to Herpes simplex virus type 1. Substitution reactions in the N-indolic position with mono- and di-substituted alkyl, benzyl, allyl, propargyl, and ethyl acetate groups were performed, in addition to conversion to their acidic derivatives. The obtained analogs were submitted to cytotoxicity and antiviral activity screening against Herpes simplex virus type 1 by the tetrazolium microculture method. From the semi-synthesis, 14 analogs were obtained, and 12 are new. The cytotoxicity assay showed that caulerpin acid and N-ethyl-substituted acid presented cytotoxic concentrations referring to 50% of the maximum effect of 1035.0 µM and 1004.0 µM, respectively, values significantly higher than caulerpin. The antiviral screening of the analogs revealed that the N-substituted acids with methyl and ethyl groups inhibited Herpes simplex virus type 1-induced cytotoxicity by levels similar to the positive control acyclovir.

Efficient synthesis of novel 1,10 phenanthroline-substituted imidazolium salts: Exploring their anticancer applications

This study reports a new series of 1,10-phenanthroline-substituted imidazolium salts (1a–f), examining their design, synthesis, structure and anticancer activities. The structures of these salts (1a–f) were characterized using 1H, 13C NMR, elemental analysis, mass spectrometry and Fourier transform infrared (FT-IR) spectroscopies. The salts' cytotoxic activities were tested against cancer cell lines, specifically MCF-7, MDA-MB-231 and non-tumorigenic MCF-10A mammary cells. The study compared the impact of aliphatic and benzylic groups in the salts’ structure on their anticancer activity. Screening results revealed that compound 1c, in particular, showed promising inhibitory activity against the growth of MDA-MB-231 breast cancer cells, with an IC50 value of 12.8 ± 1.2 μM, indicating its potential as a chemotherapeutic agent. Cell apoptosis analysis demonstrated a tendency for compound 1c to induce early apoptosis in breast cancer cells. The stability/aquation of compound 1c was investigated using 1H NMR spectroscopy and its binding modes with DNA were explored via UV–Vis spectroscopy. Additionally, the study investigated the interaction residues and docking scores of compound 1c and the reference drug doxorubicin against Bax and Bcl-2 proteins using molecular docking.

Nitrofuran Derivatives with Benzyl Groups are Promising Candidates as Antibacterial Agents Against Staphylococcus epidermidis

AbstractStaphylococcus epidermidis is a particular concern due to its high resistance to most antibiotics. We designed and synthesised a series of nitrofuran derivatives based on the chemical structure of nitrofurantoin. Among these derivatives, compared to nitrofurantoin, the nitrofuran derivatives with n‐alkyl groups did not effectively inhibit S. aureus with minimum inhibitory concentrations (MIC) values ranging from 16 to >128 μM, while these with benzyl groups displayed potent antibacterial activity against S. aureus with MIC values ranging from 4 to 16 μM. It suggests benzyl groups play an important role in the nitrofuran derivatives against S. aureus. The nitrofuran derivatives with benzyl groups also displayed potent antibacterial activity against S. epidermidis with MIC values ranging from 2 to 8 μM. Especially, compound 20 exhibited MIC 2 μM (0.814 μg/mL) against S. epidermidis. The CC50s of compound 20 in 293 T cells and LX‐2 cells were 3.131 μg/mL and 30.51 μg/mL, respectively. While at 128 μg/mL of compound 20, no obvious red blood cell rupture was observed. It showed minimal cytotoxicity and hemolytic activity. These findings suggest that compound 20 could function as a potential antibacterial agent for treating Urinary tract infections (UTIs) caused by S. epidermidis.

Co(II) Macrocyclic Complexes with Amide-Glycinate Pendants as ParaCEST and Liposomal CEST Agents.

Macrocyclic Co(II) complexes with appended amide-glycinate groups were prepared to develop paramagnetic Co(II) chemical exchange saturation transfer (CEST) agents of reduced overall charge. Complexes with reduced charge and lowered osmolarity are important for their loading into liposomes and to provide complexes that are highly water soluble and well tolerated in animals. Co(L1) has two non-coordinating benzyl groups and two amide-glycinate pendants, whereas Co(L2) has two unsubstituted amide pendants and two amide-glycinate pendants on cyclam (1,4,8,11-tetraazacyclododecane). The 1H NMR spectrum of Co(L1) is consistent with a single cis-pendant isomer with both amide protons in the trans-configuration, as supported by an X-ray crystal structure. Co(L2) has a mixture of different isomers in solution, including the trans-1,4 and 1,8 pendant isomers. The Z-spectrum of Co(L1) shows one highly-shifted CEST peak, whereas Co(L2) exhibits six CEST peaks. Encapsulation of 40 mM Co(L1) in a liposome with osmotically-induced shrinking at 300 mOsm/L produces a liposomal CEST agent with saturation frequency offset of 3 ppm. Addition of the amphiphilic 1,4,7-triazacyclononane-based complex Co(L5) to the liposomal bilayer at 18 mM with Co(L1) encapsulated in the liposome at 50 mM changes the sign and increases the magnitude of the saturation frequency offset to -7.5 ppm at 300 mOsm/L.

Structure-Activity Relationship Study of CYM51010, an agonist for the µ-δ Opioid Receptor Heterodimer.

Although opioid analgesics are indispensable in treating pain, these drugs are accompanied by life-threatening side effects. While clinically relevant opioid drugs target the µ opioid receptor (MOR), a heterodimer between the MOR and the δ opioid receptor (DOR) has emerged as another target to develop safer analgesics. Although some heterodimer-preferring agonists have been reported so far, it is still difficult to activate the MOR/DOR heterodimer selectively in the presence of MOR or DOR monomers/homodimers. To gain insights to develop selective agonists for MOR/DOR, herein we prepared analogs of CYM51010, one of the reported heterodimer-preferring agonists, and collected structure-activity relationship information. We found that the ethoxycarbonyl group was needed for the activity for the heterodimer, although this group could be substituted with functional groups with similar sizes, such as an ethoxycarbonyl group. As for the acetylaminophenyl group, not a type of substituent, but rather a substituent located at a specific position (para-position) was essential for the activity. Changing the linker length between the acetylaminophenyl group and the piperidine moiety also had deleterious effects on the activity. On the other hand, the substitution of the acetylamino group with a trifluoroacetylamino group and the substitution of the phenethyl group with a benzyl group diminished the activities for the monomers/homodimers while keeping the activity for MOR/DOR, which enhanced the selectivity. Our findings herein will play an important role in developing selective agonists for MOR/DOR and for elucidating the physiological roles of this heterodimer in analgesic processes and in the establishment of side effects.

Structure-Functional Activity of Pyrone Derivatives for Inhibition of Barnacle Settlement and Biofilm Formation.

Naturally occurring 6-pentyl-2H-pyran-2-one and its synthetic analogues greatly inhibit the settlement of Amphibalanus amphitrite cyprids and the growth and biofilm formation of marine bacteria. To optimize the antifouling activities of pyrone derivatives, this study designed pyrone analogues by modifying functional groups, such as the benzyl group, cyclopentane, and halides, substituted on both sides of a pyrone. The antifouling effects of the synthesized pyrone derivatives were subsequently evaluated against five marine biofilm-forming bacteria, Loktanella hongkongensis, Staphylococcus cohnii, S. saprophyticus, Photobacterium angustum, and Alteromonas macleodii, along with barnacle cyprids of Amphibalanus amphitrite. Substituting nonpolar parts-such as the aliphatic, cyclopentyl, or phenyl moieties on C-5 or the furan moieties on C-3-not only increased antibacterial activity and inhibited biofilm formation but also inhibited barnacle cyprid settlement when compared to 6-pentyl-2H-pyran-2-one.

Diastereoselective 1,3-dipolar intramolecular nitrone olefin cycloaddition (INOC) reaction of a sugar-derived allyl alcohol: Synthesis of functionalized aminocyclopentitols

The DIBAL-H reduction of the Baylis-Hillman sugar adduct, obtained from 3-O-benzyl-1,2-isopropylidene-α-D-xylo-pentodialdo-1,4-furanose yielded trisubstituted alkenes by eliminating the β-hydroxyl group. Subsequently, the hydrolysis of the isopropylidene acetal to the corresponding hemiacetal was reacted with N-benzyl hydroxylamine hydrochloride to generate the nitrone, which underwent diastereoselective intramolecular 1,3-dipolar nitrone olefin cycloaddition (INOC) to give an isoxazolidine skeleton. The concomitant reductive cleavage of the N-O bond and benzyl group of the fused isoxazolidines afforded new functionalized aminocyclopentitols in good yields.

Exploring Favorable Supramolecular Interactions of Multifluorinated Aromatics in Dendronized Push-Pull Chromophores for Electro-Optics.

Multifluorinated aromatics serve as supramolecular synthons in the research of organic electro-optic (EO) materials by exploiting π-π stacking interaction between the aromatic hydrocarbon and multifluorinated aromatic groups for performance improvement. However, non-classical hydrogen bonding remains largely unexplored in fluorinated EO dendrimers. In this study, three Fréchet-type generation 1 benzyl ether co-dendrons were synthesized by replacing one benzyl group with 2,3,5,6-tetrafluorobenzyl (p-HF4Bz), pentafluorobenzyl (C6F5Bz), and 2,3,4,5-tetrafluorobenzyl (o-HF4Bz) groups, to afford the benzoic acid derivatives D1, D2, and D3, which were further bonded to the donor and π-bridge moieties to afford three co-dendronized push-pull phenyltetraene chromophores EOD1, EOD2, and EOD3, respectively. The weak C-H⋅⋅⋅X (X=O, F) interactions in the crystal structure of D1 cumulatively add to the benzoic acid dimers to form an extended hydrogen-bonded network, while D2 is crystallized into a centric one-dimensional chain with strong intermolecular interactions. The poled films of EOD1 with PMMA exhibited the largest and most stable EO activity with optical homogeneity among the series. The results identify the effectiveness of weak but favorable hydrogen bonds enabled by the enhanced carbon acidity of p-HF4Bz synthon in D1, over the interactions in D2 and D3, for the rational design of supramolecular EO dendrimers.

Regulation of exercise ability and glycolipid metabolism by synthetic SR9009 analogues as new REV-ERB-α agonists

SR9009 is an activator of REV-ERBs with diverse biological activities, including improving exercise tolerance and controlling skeletal muscle mass. To optimise the carbamate motif of SR9009, analogues of SR9009 were synthesised and evaluated. All of them showed REV-ERB-α agonist activities. Among them, 5a, 5f, 5 g, 5m, and 5p showed potencies equivalent to or slightly higher than the potency of SR9009 in vitro. These data indicate that the halogenated benzyl group is an indispensable active group in these compounds. 5m, 5p and SR9009 improved exercise tolerance in normal mice in vivo. Additionally, in hyperlipidemic mice, 5m and 5p not only improved exercise tolerance but also lowered blood lipid levels. 5m and 5p displayed stronger hypoglycaemic activity than SR9009.