Potent, selective and reversible hMAO-B inhibition by benzalphthalides: Synthesis, enzymatic and cellular evaluations and virtual docking and predictive studies.

Monoaminooxidases (MAOs) are important targets for drugs used in the treatment of neurological and psychiatric disorders and particularly on Parkinson's Disease (PD). Compounds containing a trans-stilbenoid skeleton have demonstrated good selective and reversible MAO-B inhibition. Here, twenty-two (Z)-3-benzylidenephthalides (benzalphthalides, BPHs) displaying a trans-stilbenoid skeleton have been synthesised and evaluated as inhibitors of the MAO-A and MAO-B isoforms. Some BPHs have selectively inhibited MAO-B, with IC50 values ranging from sub-nM to µM. The most potent compound with IC50 = 0.6 nM was the 3',4'-dichloro-BPH 16, which showed highly selective and reversible MAO-B inhibitory activity. Furthermore, the most selective BPHs displayed a significant protection against the apoptosis, and mitochondrial toxic effects induced by 6-hydroxydopamine (6OHDA) on SH-SY5Y cells, used as a cellular model of PD. The results of virtual binding studies on the most potent compounds docked in MAO-B and MAO-A were in agreement with the potencies and selectivity indexes found experimentally. Additionally, related to toxicity risks, drug-likeness and ADME properties, the predictions found for the most relevant BPHs in this research were within those ranges established for drug candidates.

Novel mandelic acid derivatives containing piperazinyls as potential candidate fungicides against Monilinia fructicola: Design, synthesis and mechanism study.

Brown rot of stone fruit, a disease caused by the ascomycete fungus Monilinia fructicola, has caused significant losses to the agricultural industry. In order to explore and discover potential fungicides against M. fructicola, thirty-one novel mandelic acid derivatives containing piperazine moieties were designed and synthesized based on the amide skeleton. Among them, target compound Z31 exhibited obvious in vitro antifungal activity with the EC50 value of 11.8 mg/L, and significant effects for the postharvest pears (79.4 % protective activity and 70.5 % curative activity) at a concentration of 200 mg/L. Antifungal activity for the target compounds was found to be significantly improved by the large steric hindrance of the R1 groups and the electronegative of the piperazines in the molecular structure, according to a three-dimensional quantitative structure-activity relationship (3D-QSAR) analysis. Further mechanism studies have demonstrated that the compound Z31 can disrupt cell membrane integrity, resulting in increased membrane permeability, release of intracellular electrolytes, and affect the normal growth of hyphae. Additional, morphological study also indicated that Z31 may disrupt the integrity of the membrane by inducing generate excess endogenous reactive oxygen species (ROS) and resulting in the peroxidation of cellular lipids, which was further verified by the detection of malondialdehyde (MDA) content. These studies have provided the basis for the creation of novel fungicides to prevent brown rot in stone fruits.

New cyclometalated iridium(III) complexes bearing substituted 2-(1H-benzimidazol-2-yl)quinoline: Synthesis, characterization, electrochemical and anticancer studies.

New iridium(III) compounds (C1-C3) bearing 2-(1H-benzimidazol-2-yl)quinoline ligands with different side groups (benzyl, 2,3,4,5,6-pentamethylbenzyl and 2,3,4,5,6-pentafluorobenzyl) were synthesized and characterized by using spectroscopic analyses. The effects of different side groups of iridium compounds on the photophysical and electrochemical properties have been investigated. The cytotoxicity and apoptosis of the compounds have been evaluated on breast cancer cell lines using various methods including MTT assay, flow cytometry, qRT-PCR, and colony formation. The cytotoxicity of C1, expressed as IC50 values, was found to be 11.76 µM for MDA-MB-231 and 5.35 µM for MCF-7 cells. For C3, the IC50 value was 16.22 µM for MDA-MB-231 and 8.85 µM for MCF-7 cells. In both cell lines, increased levels of Bax and caspase 3, along with downregulation of BCL-2 and positive annexin V staining, were observed, confirming apoptosis. Moreover, the colony-forming abilities in both cell lines decreased after C1 and C3 complex treatment. All these results suggest that the compounds C1 and C3 may have potential in the treatment of breast cancer, though further research is needed to confirm their efficacy.

Design and synthesis of a monocyclic derivative as a selective ACC1 inhibitor by chemical modification of biphenyl ACC1/2 dual inhibitors.

A structure-activity relationship (SAR) study towards novel ACC1-selective inhibitors was carried out by modifying the molecular length of the linker in biaryl derivative 1 g, an ACC1/2 dual inhibitor. Ultimately, this leads us to discover novel phenoxybenzyloxy derivative 1i as a potent ACC1-selective inhibitor. Further chemical modification of this scaffold to improve cellular potency as well as physicochemical and pharmacokinetic (PK) properties produced N-2-(pyridin-2-ylethyl)acetamide derivative 1n, which showed highly potent ACC1-selective inhibition as well as sufficient PK profile for further in vivo evaluations. Oral administration of 1n significantly reduced the concentration of malonyl-CoA in HCT-116 xenograft tumors at doses of 100 mg/kg. Accordingly, our novel series of potent ACC1-selective inhibitors represents a set of useful orally-available research tools, as well as potential therapeutic agents for cancer and fatty acid-related diseases.

Synthesis and in vitro antileishmanial efficacy of benzyl analogues of nifuroxazide.

Leishmaniasis is a vector-borne parasitic disease that mostly affects populations in tropical and subtropical countries. There is currently no vaccine to protect against and only a handful of drugs are available to treat this disease. Leishmaniasis is curable, but its eradication and elimination are hindered by the emergence of multidrug resistant strains of the causative pathogens, accentuating the need for new and effective antileishmanial drugs. In search for such agents, nifuroxazide, a clinical antibiotic, was evaluated through investigation of its benzyl analogues for in vitro antileishmanial efficacy against promastigotes of various Leishmania (L.) strains. The monobenzylated analogues 1 and 2 were the most potent of all, possessing nanomolar activities up to 10-fold higher than the parent drug nifuroxazide against all three tested Leishmania strains. Both analogues stand as antipromastigote hits for further lead investigation into their potential to act as new antileishmanial agents.

Novel (+)-Neoisopulegol-Based O-Benzyl Derivatives as Antimicrobial Agents.

Discovery of novel antibacterial agents with new structures, which combat pathogens is an urgent task. In this study, a new library of (+)-neoisopulegol-based O-benzyl derivatives of aminodiols and aminotriols was designed and synthesized, and their antimicrobial activity against different bacterial and fungal strains were evaluated. The results showed that this new series of synthetic O-benzyl compounds exhibit potent antimicrobial activity. Di-O-benzyl derivatives showed high activity against Gram-positive bacteria and fungi, but moderate activity against Gram-negative bacteria. Therefore, these compounds may serve a good basis for antibacterial and antifungal drug discovery. Structure-activity relationships were also studied from the aspects of stereochemistry of the O-benzyl group on cyclohexane ring and the substituent effects on the ring system.

Divergent Synthesis of Natural Benzyl Salicylate and Benzyl Gentisate Glucosides.

Herein is reported the first total synthesis of benzyl salicylate and benzyl gentisate glucosides present in various plant species, in particular the Salix genus, such as Populus balsamifera and P. trichocarpa. The method permits the synthesis of several natural phenolic acid derivatives and their glucosides starting from salicylic or gentisic acid. The divergent approach afforded access to three different acetylated glucosides from a common synthetic intermediate. The key step in the total synthesis of naturally occurring glycosides-the selective deacetylation of the sugar moiety-was achieved in the presence of a labile benzyl ester group by employing mild deacetylation conditions. The protocol permitted synthesis of trichocarpine (4 steps, 40% overall yield), isotrichocarpine (3 steps, 51% overall yield), trichoside (6 steps, 40% overall yield), and deoxytrichocarpine (3 steps, 42% overall yield) for the first time (>95% purity). Also, the optimized mild deacetylation conditions allowed synthesis of 2-O-acetylated derivatives of all four glycosides (5-17% overall yield, 90-95% purity), which are rare plant metabolites.

Design and synthesis of 3-benzylaminocoumarin-7-O-sulfamate derivatives as steroid sulfatase inhibitors.

Steroid sulfatase (STS) is a sulfatase enzyme that catalyzes the conversion of sulfated steroid precursors to free steroid. The inhibition of STS could abate estrogenic steroids that stimulate the proliferation and development of breast cancer, and therefore STS is a potential target for adjuvant endocrine therapy. In this study, a series of 3-benzylaminocoumarin-7-O-sulfamate derivatives targeting STS were designed and synthesized. Structure-relationship activities (SAR) analysis revealed that attachment of a benzylamino group at the 3-position of coumarin improved inhibitory activity. Compound 3j was found to have the highest inhibition activity against human placenta isolated STS (IC50  0.13 µM) and MCF-7 cell lines (IC50 1.35 µM). Kinetic studies found compound 3j to be an irreversible inhibitor of STS, with KI and kinact value of 86.9 nM and 158.7 min-1, respectively.

Introduction of Para-Hydroxy Benzyl Spacer Greatly Expands the Utility of Ortho-Hydroxy-Protected Aryl Sulfate System: Application to Nonphenolic Payloads.

The ortho-hydroxy-protected aryl sulfate (OHPAS) linker is composed of a diaryl sulfate backbone equipped with a latent phenol moiety at the ortho position of one of the aryl units. The Ar-OH released when the ortho phenol undergoes intramolecular cyclization and displaces the second aryl unit can be viewed as a payload. We have shown in the preceding paper that the OHPAS linkers are highly stable chemically and in various plasmas, yet release payloads when exposed to suitable triggering conditions. As an extension of the OHPAS system, we employed a para-hydroxy benzyl (PHB) spacer for coupling to nonphenolic payloads; this tactic again provided a highly stable system capable of smooth release of appended payloads. The PHB modification works beautifully for tertiary amine and N-heterocycle payloads.

Design, synthesis and antitumour and anti-angiogenesis evaluation of 22 moscatilin derivatives.

Two series of moscatilin derivatives were designed, synthesized and evaluated as anti-tumor and anti-angiogenesis agents. Most of these compounds showed moderate-to-obvious cytotoxicity against five cancer cell lines (A549, HepG2, MDA-MB-231, MKN-45, HCT116). Among these cell lines, compounds had obvious effects on HCT116. Especially for 8Ae, the IC50 was low to 0.25 µM. 8Ae can inhibit the viability and induce the apoptosis of HCT116 cells but exhibit no cytotoxic activity in noncancerous NCM460 colon cells. 8Ae can also arrest the G2/M cell cycle in HCT116 cells by inhibiting the α-tubulin expression. Zebrafish bioassay-guided screen showed the 22 moscatilin derivatives had potent anti-angiogenic activities and compound 8Ae had better activities than positive compound. Molecular docking indicated 8Ae interacted with tubulin at the affinity of -7.2 Kcal/mol. In conclusion, compound 8Ae was a potential antitumor and anti-angiogenesis candidate for further development.

New benzyl pyridinium derivatives bearing 2,4-dioxochroman moiety as potent agents for treatment of Alzheimer's disease: Design, synthesis, biological evaluation, and docking study.

A new series of benzyl pyridinium-2,4-dioxochroman derivatives 7a-o was synthesized and evaluated as new anti-Alzheimer agents. Among the synthesized compounds, the compounds 7f and 7i exhibited the most potent anti-AChE and anti-BuChE activities, respectively. The kinetic study of the compound 7f revealed that this compound inhibited AChE in a mixed-type inhibition mode. Furthermore, the docking study of the compounds 7f and 7i showed that these compounds bound to both the catalytic site (CS) and peripheral anionic site (PAS) of AChE and BuChE, respectively. The compound 7f also exhibited a greater self-induced Aß peptide aggregation inhibitory activity in compare to donepezil. Furthermore, the neuroprotective activity of this compound at 20 µM was comparable to that of the standard neuroprotective agent (quercetin).

Isolation and Structure-Activity Relationship of Subergorgic Acid and Synthesis of Its Derivatives as Antifouling Agent.

In this study, as part of our continuous search for environmentally-friendly antifoulants from natural resources, subergorgic acid (SA) was identified from the gorgonian coral Subergorgia suberosa, demonstrating non-toxic, significant inhibitory effects (EC50 1.25 µg/mL, LC50 > 25 µg/mL) against the settlement of Balanus amphitrite. To further explore the bioactive functional groups of SA and synthesize more potent antifouling compounds based on the lead SA, the structure-activity relationships of SA were studied, followed by rational design and synthesis of two series of SA derivatives (one being benzyl esters of SA and another being SA derivatives containing methylene chains of various lengths). Our results indicated that (1) both the double bond and ketone carbonyl are essential elements responsible for the antifouling effect of SA, while the acid group is not absolutely necessary for maintaining the antifouling effect; (2) all benzyl esters of SA displayed good antifouling effects (EC50 ranged from 0.30 to 2.50 µg/mL) with the most potent compound being 5 (EC50 0.30 µg/mL, LC50 > 25 µg/mL), which was over four-fold more potent than SA; and (3) the introduction of a methylene chain into SA reduces the antifouling potency while the length of the methylene chain may differently influence the antifouling effect, depending on the functional group at the opposite site of the methylene chain. Not only has this study successfully revealed the bioactive functional groups of SA, contributing to the mechanism of SA against the settlement of B. amphitrite, but it has also resulted in the identification of a more potent compound 5, which might represent a non-toxic, high-efficiency antifoulant.

Acid Catalyzed Formation of C⁻C and C⁻S Bonds via Excited State Proton Transfer.

The behavior of 2-naphthol and 7-bromo-2-naphthol as organic photoacids are exploited in organic synthesis for the preparation of benzyl sulfides (using a trichloroacetimidate derivative as the starting substrate) and polycyclic amines via acid catalyzed condensation of 1,2,3,4-tetrahydroisoquinoline with aldehydes.

The Synthesis of ³H-Labelled 8-Azido-N6-Benzyladenine and Related Compounds for Photoaffinity Labelling of Cytokinin-Binding Proteins.

The biology of the group of plant hormones termed cytokinins is reviewed to reveal areas where further studies of cytokinin-binding proteins could be significant. Such areas include: inhibition of human tumour cell growth by cytokinin ribosides, the role of cytokinins in the development of diverse micro-organisms including the cyanobacteria and Mycobacterium tuberculosis, the very rapid responses of plant cells to exogenous cytokinins, and other aspects of cytokinin plant biology. Photoaffinity labelling (PAL) coupled to the recent advances in HPLC of proteins and mass spectral analysis and sequencing of proteins, may have relevance to these areas. To facilitate PAL, we present experimental details for two methods for synthesis of 8-azido-N6-benzyladenine, which has the azido affinity group in the preferred position of the purine ring. Synthesis from [2-³H]adenosine yielded the above-mentioned PAL reagent with ³H in the purine ring and also gave labelled 9-riboside and 8-azido-N6,9-dibenzyladenine. 8-Azido-N6-benzyladenine was also prepared from 6,8-dichloropurine by a facile synthesis, which would allow a label to be sited in the benzyl group where substituents can also be introduced to vary cytokinin activity. The use of inactive cytokinin analogues in assessing the significance of PAL is discussed.

Antineoplastic activity of linear leucine homodipeptides and their potential mechanisms of action.

Galaxamide is a rare cyclic homopentapeptide composed of three leucines and two N-methyl leucines isolated from marine algae Galaxaura filamentosa. The strong antitumor activity of this compound makes it a promising candidate for tumor therapy. The synthesis of galaxamide, however, is a complex process, and it has poor water solubility. On the basis of its special chemical composition, we designed a series of linear leucine homopeptides. Among seven dipeptide derivatives, five compounds with terminal protection groups and methyl substitution of the hydrogen in the amido group showed remarkable inhibitory effects against various cancer cells. N-tertbutyl-D-leucine-N-methyl-D-leucinebenzyl (A7), the only stereomer condensed by two D-leucines, showed the highest antineoplastic activity. A7-treated cells showed cell cycle arrest and morphological changes typical of cells undergoing apoptosis. The population of Annexin-V positive/propidium iodide-negative cells also increased, indicating the induction of early apoptosis. A7 promoted the cleavage of caspase-9 and caspase-3, as well as increased intracellular Ca levels and decreased the mitochondrial membrane potential. Collectively, certain linear leucine dipeptides derived from cyclic pentapeptide are able to inhibit tumor cell proliferation through cell cycle arrest and apoptosis induction. The N-methyl group in the side chain and the D/L conformation of the amino-acid residue are critical for their activity.

meta-Cyanobenzyl substituted benzimidazolium salts: Synthesis, characterization, crystal structure and carbonic anhydrase, α-glycosidase, butyrylcholinesterase, and acetylcholinesterase inhibitory properties.

meta-Cyanobenzyl-substituted N-heterocyclic carbene (NHC) precursors were synthesized by the reaction of a series of N-(alkyl)benzimidazolium with 3-bromomethyl-benzonitrile. These benzimidazolium salts were characterized by using 1 H NMR, 13 C NMR, FTIR spectroscopy, and elemental analysis techniques. The molecular and crystal structures of 2f and 2g complexes were obtained by using the single-crystal X-ray diffraction method. The derivatives of these novel NHC precursors were effective inhibitors of α-glycosidase (AG), the cytosolic carbonic anhydrase I and II isoforms (hCA I and II), butyrylcholinesterase (BChE), and acetylcholinesterase (AChE) with Ki values in the range of 1.01-2.12 nM for AG, 189.56-402.44 nM for hCA I, 112.50-277.37 nM for hCA II, 95.45-352.58 nM for AChE, and 132.91-571.18 nM for BChE. In the last years, inhibition of the CA enzyme has been considered as a promising factor for pharmacologic intervention in a diversity of disturbances such as obesity, glaucoma, cancer, and epilepsy.

Ferrocene-Containing Impiridone (ONC201) Hybrids: Synthesis, DFT Modelling, In Vitro Evaluation, and Structure⁻Activity Relationships.

Inspired by the well-established clinical evidence about the interplay between apoptotic TRAIL (tumour necrosis factor-related apoptosis-inducing ligand) mechanism and reactive oxygen species (ROS)-mediated oxidative stress, a set of novel ONC201 hybrids containing the impiridone core and one or two differently positioned ferrocenylalkyl groups were synthesised in our present work. These two types of residues have been implicated in the aforementioned mechanisms associated with cytotoxic activity. A straightforward, primary amine-based synthetic approach was used allowing the introduction of a variety of N-substituents into the two opposite regions of the heterocyclic skeleton. Reference model compounds with benzyl and halogenated benzyl groups were also synthesised and tested. The in vitro assays of the novel impiridones on five malignant cell lines disclosed characteristic structure-activity relationship (SAR) featuring significant substituent-dependent activity and cell-selectivity. A possible contribution of ROS-mechanism to the cytotoxicity of the novel metallocenes was suggested by density functional theory (DFT)studies on simplified models. Accordingly, unlike the mono-ferrocenylalkyl-substituted products, the compounds containing two ferrocenylalkyl substituents in the opposite regions of the impiridone core display a much more pronounced long-term cytotoxic effect against A-2058 cell line than do the organic impiridones including ONC201 and ONC212. Furthermore, the prepared bis-metallocene derivatives also present substantial activity against COLO-205- and EBC-1 cell lines.

Molecular Insights into the Translesion Synthesis of Benzyl-Guanine from Molecular Dynamics Simulations: Structural Evidence of Mutagenic and Nonmutagenic Replication.

DNA can be damaged by many compounds in our environment, and the resulting damaged DNA is commonly replicated by translesion synthesis (TLS) polymerases. Because the mechanism and efficiency of TLS are affected by the type of DNA damage, obtaining information for a variety of DNA adducts is critical. However, there is no structural information for the insertion of a dNTP opposite an O6-dG adduct, which is a particularly harmful class of DNA lesions. We used molecular dynamics (MD) simulations to investigate structural and energetic parameters that dictate preferred dNTP insertion opposite O6-benzyl-guanine (Bz-dG) by DNA polymerase IV, a prototypical TLS polymerase. Specifically, MD simulations were completed on all possible ternary insertion complexes and ternary -1 base deletion complexes with different Bz-dG conformations. Our data suggests that the purines are unlikely to be inserted opposite anti- or syn-Bz-dG, and dTTP is unlikely to be inserted opposite syn-Bz-dG, because of changes in the active site conformation, including critical hydrogen-bonding interactions and/or reaction-ready parameters compared to natural dG replication. In contrast, a preserved active site conformation suggests that dCTP can be inserted opposite either anti- or syn-Bz-dG and dTTP can be inserted opposite anti-Bz-dG. This is the first structural explanation for the experimentally observed preferential insertion of dCTP and misincorporation of dTTP opposite Bz-dG. Furthermore, we provide atomic level insight into why Bz-dG replication does not lead to deletion mutations, which is in contrast with the replication outcomes of other adducts. These findings provide a basis for understanding the replication of related O6-dG adducts.

Second Generation Grp94-Selective Inhibitors Provide Opportunities for the Inhibition of Metastatic Cancer.

Glucose regulated protein 94 (Grp94) is the endoplasmic reticulum (ER) resident isoform of the 90 kDa heat shock protein (Hsp90) family and its inhibition represents a promising therapeutic target for the treatment of many diseases. Modification of the first generation cis-amide bioisostere imidazole to alter the angle between the resorcinol ring and the benzyl side chain via cis-amide replacements produced compounds with improved Grp94 affinity and selectivity. Structure-activity relationship studies led to the discovery of compound 30, which exhibits 540 nm affinity and 73-fold selectivity towards Grp94. Grp94 is responsible for the maturation and trafficking of proteins associated with cell signaling and motility, including select integrins. The Grp94-selective inhibitor 30 was shown to exhibit potent anti-migratory effects against multiple aggressive and metastatic cancers.

One-step preparation of enantiopure L- or D-amino acid benzyl esters avoiding the use of banned solvents.

The enantiomers of amino acid benzyl esters are very important synthetic intermediates. Many of them are currently prepared by treatment with benzyl alcohol and p-toluenesulfonic acid in refluxing benzene or carbon tetrachloride, to azeotropically remove water, and then precipitated as tosylate salt by adding diethyl ether. Here, we report a very efficient preparation of eight L- or D-amino acid benzyl esters (Ala, Phe, Tyr, Phg, Val, Leu, Lys, Ser), in which these highly hazardous solvents are dismissed using cyclohexane as a water azeotroping solvent and ethyl acetate to precipitate the tosylate salt. With some work-up modifications and lower yield, the procedure can be applied also to methionine. Chiral HPLC analysis shows that all the benzyl esters, including the highly racemizable ones such as those of phenylglycine, tyrosine and methionine, are formed enantiomerically pure under these new reaction conditions thus validating the solvents replacement. Contrariwise, toluene cannot be used in place of benzene or carbon tetrachloride because leading to partially or totally racemized amino acid benzyl esters depending on the polar effect of the amino acid α-side chain as expressed by Taft's substituent constant (σ*).