Synthesis and Evaluation of Estrogen Agonism of Diaryl 4,5-Dihydroisoxazoles, 3-Hydroxyketones, 3-Methoxyketones, and 1,3-Diketones: A Compound Set Forming a 4D Molecular Library

Gefitinib-Tamoxifen Hybrid Ligands as Potent Agents against Triple-Negative Breast Cancer

Anticancer drug conjugates may benefit from simultaneous action at two targets potentially overcoming the drawbacks of current cancer treatment, such as insufficient efficacy, high toxicity, and development of resistance. Compared to a combination of two single-target drugs, they may offer an advantage of pharmacokinetic simplicity and fewer drug-drug interactions. Here, we report a series of compounds connecting tamoxifen or endoxifen with the EGFR-inhibitor gefitinib via a covalent linkage. These hybrid ligands retain both ER antagonist activity and EGFR inhibition. The most potent analogues exhibited single-digit nanomolar activities at both targets. The amide-linked endoxifen-gefitinib drug conjugates 17b and 17c demonstrated the most favorable anti-cancer profile in cellular viability assays on MCF7, MDA-MB-231, MDA-MB-468, and BT-549 breast cancer cells. Most importantly, in TNBC cells 17b and 17c displayed nanomolar IC₅₀-values (380 nM - 970 nM) and were superior in their anti-cancer activity compared to their control compounds and combinations thereof.

Hexahydroazulene-2(1H)-one Sesquiterpenoids with Bridged Cyclobutane, Oxetane, and Tetrahydrofuran Rings from the Stems of Daphne papyracea with α-Glycosidase Inhibitory Activity

Chemical investigation of an alcoholic extract from the stem of Daphne papyracea ("Xuehuagou") led to the isolation of the tetracyclic sesquiterpenoid daphnepapytone A (1), containing a unique caged skeleton with a cyclobutane ring having three tetrasubstituted chirality centers. Also isolated were new guaiane sesquiterpenoids, namely, daphnepapytones B-H (2-8), and one 1,5-diphenylpentanone 2-hydroxy-5-oxo-daphneone (9), together with 26 known compounds. The cyclic metabolites share a 5-isoprenyl-hexahydroazulene-2(1H)-one skeleton with different substitution patterns and a bridged cyclobutane, oxetane, or tetrahydrofuran ring. The planar structures and relative configuration of the new compounds were elucidated on the basis of spectroscopic analysis aided by DFT ¹³C NMR calculations. The absolute configurations of 1-7 were determined by X-ray single-crystal diffraction or TDDFT-ECD calculations. Daphnepapytones A and C (1 and 3), 2-hydroxy-5-oxodaphneone (9), daphnenone (10), daphneone (11), and 3-methyldaphneolone (12) showed α-glycosidase inhibitory activity, with IC₅₀ values of 159.0, 102.3, 139.3, 43.3, 145.0, and 126.1 μM, respectively.

Ni/Chiral Sodium Carboxylate Dual Catalyzed Asymmetric O-Propargylation

A highly enantioselective O-propargylation catalyzed by combining a phosphine-nickel complex and an axially chiral sodium dicarboxylate has been developed. The transformation features mild reaction conditions, a broad substrate scope, and excellent functional group tolerance, offering an efficient approach to an array of enantioenriched O-propargyl hydroxylamines. Mechanistic studies support the presumed role of the chiral carboxylate as a counterion for nickel catalysis enabling the discovery of highly stereoselective transformations. The power of this reaction is illustrated by its application in the asymmetric total synthesis of potent firefly luciferase inhibitors and (S)-dihydroyashabushiketol.

Synthesis of difluorinated 3-oxo-N,3-diarylpropanamides from 4-arylamino coumarins mediated by Selectfluor

An expeditious approach to synthesize difluorinated 3-oxo-N,3-diarylpropanamides from 4-arylamino coumarins has been accomplished in the presence of Selectfluor, which plays the dual role of a mild oxidant and a source of fluorine.

Diarylheptanoids from Rhizomes of Alpinia officinarum Inhibit Aggregation of α-Synuclein

Two new diarylheptanoids, alpinin A (1) and alpinin B (2), together with 18 known diarylheptanoids (3-20), were isolated from the rhizomes of Alpinia officinarum. Their structures were elucidated by comprehensive spectroscopic analysis, including high-resolution mass spectrometry, infrared spectroscopy, and one- and two-dimensional nuclear magnetic resonance spectroscopy. Structurally, alpinin A is a new member of the small family of oxa-bridged diarylheptanoids and contains the characteristic 2,6-cis-configured tetrahydropyran motif (C₁-C₅ oxa bridge). The absolute configuration of alpinin A was confirmed by asymmetric total synthesis of the enantiomer (ent-1), corroborating the assignment of the molecular structure. The absolute configuration of alpinin B was determined on the basis of the analysis of the circular dichroism exciton chirality spectrum. We evaluated the inhibitory activity of all isolated diarylheptanoids against α-synuclein aggregation at 10 μM. Alpinins A and B significantly inhibited α-synuclein aggregation by 66 and 67%, respectively.

Chemical Constituents of Supercritical Extracts from Alpinia officinarum and the Feeding Deterrent Activity against Tribolium castaneum

Alpinia officinarum has been confirmed to possess bioactivities against some pests. In this work, a sample was obtained from A. officinarum rhizomes by supercritical fluid CO₂ extraction (SFE). According to GC-MS analysis, the main chemical components for SFE-sample included benzylacetone (26.77%), 1,7-diphenyl-5-hydroxy-3-heptanone (17.78%), guaiacylacetone (10.03%) and benzenepropanal (7.42%). The essential oil of A. officinarum rhizomes (LD₅₀ = 20.71 μg/adult) exhibited more contact toxicity than SFE extract (LD₅₀ = 82.72 μg/adult) against Tribolium castaneum. From SFE extracts, one new compound, 1-phenyl-4-(16,17-dimethyl-9,13-octadiene)-5-isopentenyl-7-(4"-methoxyl-3"-hydroxyl-phenyl)-3-heptanone (3), together with five known compounds identified as 5-hydroxy-1,7-diphenyl-3-heptanone (1), 1,7-diphenyl-4-hepten-3-one (2), galangin (4), galangin-3-methyl ether (5) and pinocembrin (6), were isolated and their feeding deterrent activities against T. castaneum adults were assessed. It was found that compounds 1-6 had feeding deterrent activities against T. castaneum with feeding deterrent indices of 18.21%, 18.94%, 19.79%, 26.99%, 20.34%, and 35.81%, respectively, at the concentration of 1500 ppm. Hence, the essential oil and SFE extracts/compounds of A. officinarum rhizomes represent promising alternatives in the control of T. castaneum adults.

Facile Synthesis of Natural Alkoxynaphthalene Analogues from Plant Alkoxybenzenes

Analogues of the bioactive natural alkoxynaphthalene pycnanthulignene D were synthesized by an efficient method. The starting plant allylalkoxybenzenes (1) are easily available from the plant essential oils of sassafras, dill, and parsley. The target 1-arylalkoxynaphthalenes (5) exhibited antiproliferative activity in a phenotypic sea urchin embryo assay.

Improved assays for xenosensor activation based on reverse transfection

Discovery of receptor-dependent mechanisms for regulation of drug metabolism has provided a new way to evaluate the propensity of drug candidates to cause induction of cytochrome P450 enzymes. Therefore, receptor-based reporter assays have become common in early stages of drug development projects and in mechanistic studies. Here, we report a reverse transfection system to conduct activation assays for human xenosensors AhR, CAR and PXR. The assay format is based on long-term stability and uniformity of DNA/carrier complexes on culture plates, avoiding multiple stages and variation inherent in conventional transfection methods. Consequently, these improved assays are streamlined, reproducible and formally validated with Z' factors exceeding 0.5. This novel reverse transfection system is expected to find use in diverse areas of early drug development such prediction of CYP induction, evaluation of species differences and in mechanistic studies.

Firefly luciferase inhibitor-conjugated peptide quenches bioluminescence: a versatile tool for real time monitoring cellular uptake of biomolecules

In this paper, novel firefly luciferase-specific inhibitor compounds (FLICs) are evaluated as potential tools for cellular trafficking of transporter conjugates. As a proof-of-concept, we designed FLICs that were suitable for solid phase peptide synthesis and could be covalently conjugated to peptides via an amide bond. The spacer between inhibitor and peptide was optimized to gain efficient inhibition of recombinant firefly luciferase (FLuc) without compromising the activity of the model peptides. The hypothesis of using FLICs as tools for cellular trafficking studies was ensured with U87Fluc glioblastoma cells expressing firefly luciferase. Results show that cell penetrating peptide (penetratin) FLIC conjugate 9 inhibited FLuc penetrated cells efficiently (IC50 = 1.6 μM) and inhibited bioluminescence, without affecting the viability of the cells. Based on these results, peptide-FLIC conjugates can be used for the analysis of cellular uptake of biomolecules in a new way that can at the same time overcome some downsides seen with other methods. Thus, FLICs can be considered as versatile tools that broaden the plethora of methods that take advantage of the bioluminescence phenomena.

Ligand specificity of constitutive androstane receptor as probed by induced-fit docking and mutagenesis

Constitutive androstane receptor (CAR, NR1I3) belongs to the nuclear receptor family of transcription factors and acts as a chemical sensor of drugs and endogenous compounds. The ligand-binding preferences of CAR are diverse, and more importantly, there are significant species differences in ligand specificity. Here, we show that while certain residues are critical for the basal activity of mouse CAR (mCAR) and/or affect the binding of all tested ligands, mutation of some ligand-binding pocket (LBP) residues (e.g., F171 and Y336) paradoxically decreased the activity of a specific ligand while increasing that of others. Comparisons to previously reported human CAR (hCAR) residues indicated that the function of key CAR residues (e.g., N175, L253) is dramatically different between species. The docking results provide some mechanistic rationale for the ability of 17alpha-ethinyl-3,17beta-estradiol (EE2) to both activate mCAR and repress hCAR.