Recent advances in α,β-unsaturated carbonyl compounds as mitochondrial toxins

Asymmetric (4+1) Annulations by Cascade Allylation and Transient σ-Alkyl-Pd(II) Initiated Allylic Csp3 -H Activation

A unique Pd-catalyzed approach for asymmetric (4+1) annulations via cascade allylation and transient σ-alkyl-Pd(II) initiated methylene Csp3 -H activation is reported. The enolate fragment derived from the decarboxylation of vinyl methylene carbonate is crucial to stabilize the key intermediate. These reactions enable the synthesis of various useful dihydrobenzofurans with excellent enantioselectivity, typically >95 : 5 er, and exclusive (Z)-stereoselectivity. Compared with the well-established annulations via Heck-type C-H activations, this protocol showcases a conceptually new way to generate σ-alkyl-Pd(II) species that could initiate challenging asymmetric Csp3 -H activations.

Donor-Acceptor Covalent Organic Frameworks as a Heterogeneous Photoredox Catalyst for Scissoring Alkenes to Carbonyl Constituents

The conversion of alkenes to carbonyl constituents via the cleavage of the C═C bond is unique due to its biological and pharmacological significance. Though a number of oxidative C═C cleavage protocols have been demonstrated for terminal and electron-rich alkene systems, none of them were optimized for electron-deficient and conjugated alkenes. In this work, a covalent organic framework containing triphenylamine and triazine units was revealed to cleave the C═C bond of alkenes under very mild conditions involving visible light irradiation due to its photoredox property. The alkenes can be conveniently broken across the double bond to their constituent carbonyl derivatives on light irradiation in the presence of air and the covalent organic framework photocatalyst. This protocol is applicable for a wide range of alkenes in an aqueous acetonitrile medium with high functional group tolerance and regioselectivity. Though the electron-deficient alkenes required tetramethylethylene diamine as a sacrificial donor, the electron-rich alkenes do not demand any additives.

Discovery of N-Phenylpropiolamide as a Novel Succinate Dehydrogenase Inhibitor Scaffold with Broad-Spectrum Antifungal Activity on Phytopathogenic Fungi

Based on the structural features of both succinate dehydrogenase inhibitors (SDHIs) and targeted covalent inhibitors, a series of N-phenylpropiolamides containing a Michael acceptor moiety were designed to find new antifungal compounds. Nineteen compounds showed potent inhibition activity in vitro on nine species of plant pathogenic fungi. Compounds 9 and 13 showed higher activity on most of the fungi than the standard drug azoxystrobin. Compound 13 could completely inhibit Physalospora piricola infection on apples at 200 μg/mL concentration over 7 days and showed high safety to seed germination and seedling growth of plants at ≤100 μg/mL concentration. The action mechanism showed that 13 is an SDH inhibitor with a median inhibitory concentration, IC₅₀, value of 0.55 μg/mL, comparable with that of the positive drug boscalid. Molecular docking studies revealed that 13 can bind well to the ubiquinone-binding region of SDH by hydrogen bonds and undergoes π-alkyl interaction and π-cation interaction. At the cellular level, 1 as the parent compound could destruct the mycelial structure of P. piricola and partly dissolve the cell wall and/or membrane. Structure-activity relationship analysis showed that the acetenyl group should be a structure determinant for the activity, and the substitution pattern of the phenyl ring can significantly impact the activity. Thus, N-phenylpropiolamide emerged as a novel and promising lead scaffold for the development of new SDHIs for plant protection.

Roles of Mitochondria in Oral Squamous Cell Carcinoma Therapy: Friend or Foe?

Oral squamous cell carcinoma (OSCC) therapy is unsatisfactory, and the prevalence of the disease is increasing. The role of mitochondria in OSCC therapy has recently attracted increasing attention, however, many mechanisms remain unclear. Therefore, we elaborate upon relative studies in this review to achieve a better therapeutic effect of OSCC treatment in the future. Interestingly, we found that mitochondria not only contribute to OSCC therapy but also promote resistance, and targeting the mitochondria of OSCC via nanoparticles is a promising way to treat OSCC.

Two novel piperidones induce apoptosis and antiproliferative effects on human prostate and lymphoma cancer cell lines

Cancer remains the second most common cause of death in the US. Due to a recurrent problem with anticancer drug resistance, there is a current need for anticancer drugs with distinct modes of action for combination drug therapy We have tested two novel piperidone compounds, named 2608 (1-dichloroacetyl - 3,5-bis(3,4-difluorobenzylidene)-4-piperidone) and 2610 (1-dichloroacetyl-3,5-bis(3,4-dichlorobenzylidene)-4-piperidone), for their potential cytotoxicity on numerous human cancer cell lines. We found that both compounds were cytotoxic for breast, pancreatic, leukemia, lymphoma, colon, and fibroblast cell lines, with a cytotoxic concentration 50% (CC50) in the low micromolar to nanomolar concentration range. Further assays focused primarily on an acute lymphoblastic lymphoma and colon cancer cell lines since they were the most sensitive and resistant to the experimental piperidones. The cell death mechanism was evaluated through assays commonly used to detect the induction of apoptosis. These assays revealed that both 2608 and 2610 induced reactive oxygen species (ROS) accumulation, mitochondrial depolarization, and activated caspase-3/7. Our findings suggest that the piperidones induced cell death via the intrinsic apoptotic pathway. Additional assays revealed that both piperidones cause cell cycle alteration in lymphoma and colon cell lines. Both piperidones elicited DNA fragmentation, as evidenced by an increment in the sub-G0/G1 subpopulation in both cell lines. Similar to other related compounds, both piperidones were found to act as proteasome inhibitors by increasing the levels of poly-ubiquitinated proteins in both lymphoma and colon cell lines. Hence, the two piperidones exhibited attractive cytotoxic properties and suitable mechanisms of action, which makes them good candidates as anticancer drugs.

Apoptotic and Cell Cycle Effects of Triterpenes Isolated from Phoradendron wattii on Leukemia Cell Lines

Current antineoplastic agents present multiple disadvantages, driving an ongoing search for new and better compounds. Four lupane-type triterpenes, 3α,24-dihydroxylup-20(29)-en-28-oic acid (1), 3α,23-dihydroxy-30-oxo-lup-20(29)-en-28-oic acid (2), 3α,23-O-isopropylidenyl-3α,23-dihydroxylup-20(29)-en-28-oic acid (3), and 3α,23-dihydroxylup-20(29)-en-28-oic acid (4), previously isolated from Phoradendron wattii, were evaluated on two cell lines of chronic (K562) and acute (HL60) myeloid leukemia. Compounds 1, 2, and 4 decreased cell viability and inhibit proliferation, mainly in K562, and exhibited an apoptotic effect from 24 h of treatment. Of particular interest is compound 2, which caused arrest in active phases (G2/M) of the cell cycle, as shown by in silico study of the CDK1/Cyclin B/Csk2 complex by molecular docking. This compound [3α,23-dihydroxy-30-oxo-lup-20(29)-en-28-oic acid] s a promising candidate for incorporation into cancer treatments and deserves further study.

A multi-target directed ligands strategy for the treatment of Alzheimer's disease: Dimethyl fumarate plus Tranilast modified Dithiocarbate as AChE inhibitor and Nrf2 activator

Alzheimer's disease (AD) possessed intricate pathogenesis. Currently, multi-targeted drugs were considered to have the potential to against AD by simultaneously triggering molecules in functionally complementary pathways. Hence, a series of molecules based on the pharmacophoric features of Dimethyl fumarate, Tranilast, and Dithiocarbate were designed and synthesized. These compounds showed significant AChE inhibitory activity in vitro. Among them, compound 4c₂ displayed the mighty inhibitory activity to hAChE (IC₅₀ = 0.053 μM) and held the ability to cross the BBB. Kinetic study and molecular docking pointed out that 4c₂ bound well into the active sites of hAChE, forming steady and sturdy interactions with key residues in hAChE. Additionally, 4c₂ as an Nrf2 activator could promote the nuclear translocation of Nrf2 protein and induce the expressions of Nrf2-dependent enzymes HO-1, NQO1, and GPX4. Moreover, 4c₂ rescued BV-2 cells from H₂O₂-induced injury and inhibited ROS accumulation. For the anti-neuroinflammatory potential of 4c₂, we observed that 4c₂ could lower the levels of pro-inflammatory cytokines (NO, IL-6 and TNF-α) and suppressed the expressions of iNOS and COX-2. In particular, 4c₂ was well tolerated in mice (2500 mg/kg, p.o.) and efficaciously recovered the memory impairment in a Scopolamine-induced mouse model. Overall, these results highlighted that 4c₂ was a promising multi-targeted agent for treating AD.

New application of novel tetrazine derivatives as potent VEGFR-2 kinase inhibitors and anti-cancer agents

Background: A novel series of s-tetrazine derivatives was designed as a new scaffold and synthesized efficiently as VEGFR-2 inhibitors for the first time. Methodology & results: The inhibitory activities of the new compounds were tested by MTT assay and enzyme assay, respectively. Western blot assay, cell apoptosis assay and cell migration assay were carried out to study the action mechanism of them. All the synthesized compounds showed evident VEGFR-2 inhibitory activities (IC₅₀ in the range of 88.53-257.55 nM). Compounds 23h, 25d, 26e and 27c showed excellent anti-proliferative activities against the four tested cell lines and were better than sorafenib basically. Conclusion: Compounds with good activities based on this novel scaffold can be screened successfully.

Dichloroacetyl Amides of 3,5-Bis(benzylidene)-4-piperidones Displaying Greater Toxicity to Neoplasms than to Non-Malignant Cells

A series of 3,5-bis(benzylidene)-1-dichloroacetyl-4-piperidones 1a–l was evaluated against Ca9-22, HSC-2, HSC-3, and HSC-4 squamous cell carcinomas. Virtually all of the compounds displayed potent cytotoxicity, with 83% of the CC₅₀ values being submicromolar and several CC₅₀ values being in the double digit nanomolar range. The compounds were appreciably less toxic to human HGF, HPLF, and HPC non-malignant cells, which led to some noteworthy selectivity index (SI) figures. From these studies, 1d,g,k emerged as the lead molecules in terms of their potencies and SI values. A Quantitative Structure-Activity Relationship (QSAR) study revealed that cytotoxic potencies and potency–selectivity expression figures increased when the magnitude of the sigma values in the aryl rings was elevated. The modes of action of the representative cytotoxins in Ca9-22 cells were found to include G2/M arrest and stimulation of the cells to undergo mitosis and cause poly(ADP-ribose) polymerase (PARP) and procaspase 3 cleavage.

Photosensitized [2 + 2]-Cycloaddition of Complex Acceptor-Donor Combinations: A Regio/Diastereoselectivity Study

The photosensitized [2 + 2]-cycloaddition of chalcones, conjugated cyclopentenones, and cyclohexenones with electron-rich alkenes such as cyclic enolethers and polymethylated alkenes was investigated. While cyclic enones showed high regio- and stereoselectivity, acyclic enones resulted in a more complex product mixture containing dimers as well as four dominant regio- and diastereoisomers. This complex product mixture can be controlled by adjusting the reaction conditions such as sensitizer, solvents, or additives.

Bioassay-Guided Isolation of Nematicidal Artemisinic Acid and Dihydroartemisinic Acid from Artemisia annua L. and Evaluation of Their Activity against Meloidogyne incognita

The extract of Artemisia annua L. has been shown to possess the nematicidal activity but the potent constituents were unclear. Herein, two nematicidal sesquiterpenoid acids artemisinic acid (ArA) and dihydroartemisinic acid (DHArA) were isolated from the methanol extract of the aerial parts of A. annua L. by the bioassay-guided isolation method using Meloidogyne incognita second stage juveniles (J2s) as the screening target. The in vitro activity, control efficacy in the pot experiment, and toxic effects of these two natural compounds against M. incognita were evaluated. The in vitro results showed that the EC_50/48h values of ArA and DHArA were 0.37 mM and 0.76 mM against J2s, respectively. In the pot experiment, ArA and DHArA at the dose of 5 mg (a.i.)/pot could achieve the same level of control efficacy compared with avermectins at 2 mg (a.i.)/pot. Microscopic observations indicated the obvious toxic symptoms of J2s after ArA- and DHArA-treatment, including the shrinking body, imperfect body wall, and undiscerning organs. The physiological and biochemical studies, together with the toxic symptoms, revealed that ArA and DHArA had great impacts on the membrane system of J2s. Additionally, ArA occurring the α, β-unsaturated carbonyl was demonstrated to be reactive with glutathione (GSH) and cause the decrease of GSH content in J2s. Taken together, the present study suggests that ArA and DHArA or ArA- and DHArA-based extracts of A. annua L. have a substantial potential to be used as botanical agents for integrated disease management programs against root-knot nematodes in crop protection.

Comprehensive Target Screening and Cellular Profiling of the Cancer-Active Compound b-AP15 Indicate Abrogation of Protein Homeostasis and Organelle Dysfunction as the Primary Mechanism of Action

Dienone compounds have been demonstrated to display tumor-selective anti-cancer activity independently of the mutational status of TP53. Previous studies have shown that cell death elicited by this class of compounds is associated with inhibition of the ubiquitin-proteasome system (UPS). Here we extend previous findings by showing that the dienone compound b-AP15 inhibits proteasomal degradation of long-lived proteins. We show that exposure to b-AP15 results in increased association of the chaperones VCP/p97/Cdc48 and BAG6 with proteasomes. Comparisons between the gene expression profile generated by b-AP15 to those elicited by siRNA showed that knock-down of the proteasome-associated deubiquitinase (DUB) USP14 is the closest related to drug response. USP14 is a validated target for b-AP15 and we show that b-AP15 binds covalently to two cysteines, Cys203 and Cys257, in the ubiquitin-binding pocket of the enzyme. Consistent with this, deletion of USP14 resulted in decreased sensitivity to b-AP15. Targeting of USP14 was, however, found to not fully account for the observed proteasome inhibition. In search for additional targets, we utilized genome-wide CRISPR/Cas9 library screening and Proteome Integral Solubility Alteration (PISA) to identify mechanistically essential genes and b-AP15 interacting proteins respectively. Deletion of genes encoding mitochondrial proteins decreased the sensitivity to b-AP15, suggesting that mitochondrial dysfunction is coupled to cell death induced by b-AP15. Enzymes known to be involved in Phase II detoxification such as aldo-ketoreductases and glutathione-S-transferases were identified as b-AP15-targets using PISA. The finding that different exploratory approaches yielded different results may be explained in terms of a “target” not necessarily connected to the “mechanism of action” thus highlighting the importance of a holistic approach in the identification of drug targets. We conclude that b-AP15, and likely also other dienone compounds of the same class, affect protein degradation and proteasome function at more than one level.

Photoaffinity Probe Reveals the Potential Target of Harringtonolide for Cancer Cell Migration Inhibition

Harringtonolide (HO, 1) is a bioactive diterpenoid tropone isolated from Cephalotaxus harringtonia with antiproliferation activity. Until now there have been no reports to elucidate its anticancer mechanism. Herein we report the synthesis of HO-derived probes (10, 11, and 12) to identify the possible target of HO. As a result, the application of a novel photoaffinity alkyne-tagged probe from HO (compound 12) showed direct engagement between HO and receptor for activated C kinase 1 (RACK1). Furthermore, HO could suppress the epithelial-mesenchymal transition (EMT) process and inhibit activation of the FAK/Src/STAT3 signaling pathway in A375 cells. This study provides a groundwork for HO as an effective antitumor agent that targets RACK1 to suppress cancer cell migration.

Natural Products & Bioactivity Inspired Synthetic Pursuits Interfacing with Carbohydrates: Ongoing Journey with C-Glycosides

Natural products, remains the most important source for the discovery of new drugs for the treatment of human diseases. This has inspired the synthetic community to design and develop mimics of natural products either to answer important questions in biology or to explore their therapeutic potentials. Glycosides present themselves abundantly in nature, right from the cell surface receptors to natural products of any origin. The O-Glycosides are hydrolytically less stable compared to C-glycosides and this feature has presented a great opportunity for drug discovery. The discovery of Dapagliflozin, an SGLT inhibitor and C-glucoside, for the treatment of diabetes is one such example. Aryl acyl-anion chemistry has been explored for the synthesis of 2-deoxy-C-aryl furanoside/pyranoside/septanosides. Besides success, the studies have provided valuable insight into the natural propensities of the architectural framework for the cascade to furan derivatives. The aryl acyl-anion chemistry has also enabled the synthesis of biologically active diaryl heptanoids. Inspired from sucesss of Dapagliflozin, new analogues have been synthesized with pyridine and isocoumarin heterocycle as the proximal ring. C-glucosides of isoliquiritigenin have been synthesized for the first time and evaluated as an efficient aldose reductase inhibitor. The synthesis and evaluation of acyl-C-β-D-glucosides and benzyl-C-β-D-glucoside as glucose-uptake promoters has revealed promise in small molecules. The concept of building blocks has been used to obtain natural oxylipins, D-xylo and L-xylo-configured alkane tetrols and novel lipophilic ketones with erythro/threo configured trihydroxy polar head-group as possible anti-mycobacterial agents.

Carbonylative coupling of simple alkanes and alkenes enabled by organic photoredox catalysis

A visible-light-driven direct carbonylative coupling of simple alkanes and alkenes via the combination of a hydrogen atom transfer process and photoredox catalysis has been demonstrated. Employing the N-alkoxyazinium salt as the oxidant and the precursor of an oxygen radical, a variety of α,β-unsaturated ketones could be obtained in a metal-free fashion.

Curcumin and Its New Derivatives: Correlation between Cytotoxicity against Breast Cancer Cell Lines, Degradation of PTP1B Phosphatase and ROS Generation

Breast cancer is the most common cancer of women—it affects more than 2 million women worldwide. PTP1B phosphatase can be one of the possible targets for new drugs in breast cancer therapy. In this paper, we present new curcumin derivatives featuring a 4-piperidone ring as PTP1B inhibitors and ROS inducers. We performed cytotoxicity analysis for twelve curcumin derivatives against breast cancer MCF-7 and MDA-MB-231 cell lines and the human keratinocyte HaCaT cell line. Furthermore, because curcumin is a known antioxidant, we assessed antioxidant effects in its derivatives. For the most potent cytotoxic compounds, we determined intracellular ROS and PTP1B phosphatase levels. Moreover, for curcumin and its derivatives, we performed real-time microscopy to observe the photosensitizing effect. Finally, computational analysis was performed for the curcumin derivatives with an inhibitory effect against PTP1B phosphatase to assess the potential binding mode of new inhibitors within the allosteric site of the enzyme. We observed that two tested compounds are better anticancer agents than curcumin. Moreover, we suggest that blocking the -OH group in phenolic compounds causes an increase in the cytotoxicity effect, even at a low concentration. Furthermore, due to this modification, a higher level of ROS is induced, which correlates with a lower level of PTP1B.

Direct Access to α,β-Unsaturated Ketones via Rh/MgCl2-Mediated Acylation of Vinylsilanes

We report herein the facile and practical construction of α,β-unsaturated ketones via rhodium-catalyzed direct acylation of vinylsilanes with readily available and abundant carboxylic acids. This protocol features access to a diverse array of synthetically useful functionalities with moderate to excellent yields. More importantly, the late-stage functionalization of pharmaceuticals was also realized with synthetically useful yield.

Sensitivity of Acute Myelocytic Leukemia Cells to the Dienone Compound VLX1570 Is Associated with Inhibition of the Ubiquitin-Proteasome System

Dienone compounds with a 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore have been widely reported to show tumor cell selectivity. These compounds target the ubiquitin-proteasome system (UPS), known to be essential for the viability of tumor cells. The induction of oxidative stress, depletion of glutathione, and induction of high-molecular-weight (HMW) complexes have also been reported. We here examined the response of acute myeloid leukemia (AML) cells to the dienone compound VLX1570. AML cells have relatively high protein turnover rates and have also been reported to be sensitive to depletion of reduced glutathione. We found AML cells of diverse cytogenetic backgrounds to be sensitive to VLX1570, with drug exposure resulting in an accumulation of ubiquitin complexes, induction of ER stress, and the loss of cell viability in a dose-dependent manner. Caspase activation was observed but was not required for the loss of cell viability. Glutathione depletion was also observed but did not correlate to VLX1570 sensitivity. Formation of HMW complexes occurred at higher concentrations of VLX1570 than those required for the loss of cell viability and was not enhanced by glutathione depletion. To study the effect of VLX1570 we developed a zebrafish PDX model of AML and confirmed antigrowth activity in vivo. Our results show that VLX1570 induces UPS inhibition in AML cells and encourage further work in developing compounds useful for cancer therapeutics.

Discovery and Investigation of 1-[4-(2-Aminoethoxy)Phenylcarbonyl]- 3,5-Bis-(Benzylidene)-4-Piperidones as Candidate Antineoplastic Agents: Our Last 15 Years Study

This review outlines the discovery and development of a novel series of 1-[4-2- aminoethoxy)phenylcarbonyl]-3,5-bis-(benzylidene)-4-piperidones (5-8) as potential drug candidates over the last 15 years in our laboratory. Many of these compounds demonstrate excellent cytotoxic properties and are often more potent than contemporary anticancer drugs. Two highly important features of many of these molecules are first, the greater tumour-selective toxicity and second, the ability of these molecules to act as modulators of multi-drug resistance. The modes of action of some of the potent compounds are by apoptosis induction, generation of reactive oxygen species, activation of certain caspases and affecting mitochondrial functions. These molecules also display promising antimalarial and antimycobacterial properties. In a short term toxicity study, these molecules are well tolerated in mice. Structure-activity relationships and a drug delivery system along with pharmacokinetic studies and metabolic stability of these compounds, have been presented. The positive characteristics associated with the series (5-8) warrant their further evaluations as candidate antineoplastic drug candidates.

In Vitro Susceptibility of Kinetoplastids to Celastroloids from Maytenus chiapensis

Leishmaniasis and Chagas are among the most significant neglected tropical diseases. Due to several drawbacks with the current chemotherapy, developing new antikinetoplastid drugs has become an urgent issue. In the present work, a bioassay-guided investigation of the root bark of Maytenus chiapensis on Leishmania amazonensis and Trypanosoma cruzi led to the identification of two D:A-friedo-nor-oleanane triterpenoids (celastroloids), 20β-hydroxy-tingenone (celastroloid 5) and 3-O-methyl-6-oxo-tingenol (celastroloid 8), as promising antikinetoplastid leads. They displayed higher potency on L. amazonensis promastigotes (50% inhibitory concentrations [IC50s], 0.44 and 1.12 μM, respectively), intracellular amastigotes (IC50s, 0.83 and 1.91 μM, respectively), and T. cruzi epimastigote stage (IC50s, 2.61 and 3.41 μM, respectively) than reference drugs miltefosine and benznidazole. This potency was coupled with an excellent selectivity index on murine macrophages. Mechanism of action studies, including mitochondrial membrane potential (Δψm) and ATP-level analysis, revealed that celastroloids could induce apoptotic cell death in L. amazonensis triggered by the mitochondria. In addition, the structure-activity relationship is discussed. These findings strongly underline the potential of celastroloids as lead compounds to develop novel antikinetoplastid drugs.

Electrophilic reactivity of the Busulfan metabolite, EdAG, towards cellular thiols and inhibition of human thioredoxin-1

Busulfan is an alkylating agent used in chemotherapy conditioning regimens prior to hematopoietic stem cell transplantation (HSCT). However, its administration is associated with a great risk of adverse toxicities, which have been historically attributed to busulfan's mechanism of non-specific DNA alkylation. A phase II generated metabolite of busulfan, EdAG (γ-glutamyldehydroalanylglycine), is a dehydroalanine analog of glutathione (GSH) with an electrophilic moiety, suggesting it may bind to proteins and disrupt biological function. However, EdAG's reactions with common cellular thiols such as glutathione (GSH) and l-cysteine are understudied, along with possible inhibition of glutathionylation-dependent enzymes (with active site cysteine residues). We established a physiologically-relevant in vitro model to readily measure thiol loss over time. Using this model, we compared the apparent rates of thiol depletion in the presence of EdAG or arecoline, a toxic constituent of the areca (betel) nut and known GSH depletor. Simulated kinetic modeling revealed that the mean (±SE) alpha (α) second order rate constants describing GSH and l-cysteine depletion in the presence of EdAG were 0.00522 (0.00845) μM^-1∙min^-1 and 0.0207 (0.00721) μM^-1∙min^-1, respectively; in the presence of arecoline, the apparent rates of depletion were 0.0619 (0.009) μM^-1∙min^-1 and 0.2834 (0.0637) μM^-1∙min^-1 for GSH and l-cysteine, respectively. Under these experimental conditions, we conclude that EdAG was a weaker electrophile than arecoline. Arecoline and EdAG both depleted apparent l-cysteine concentrations to a much greater extent than GSH, approximately 4.58-fold and 3.97-fold change greater, respectively. EdAG modestly inhibited (∼20%) the human thioredoxin-1 (hTrx-1) catalyzed reduction of insulin with a mean IC₅₀ of 93 μM [95% CI: 78.6-110 μM). In summary, EdAG's ability to spontaneously react with endogenous thiols and inhibit hTrx-1 are potentially biochemically relevant in humans. These findings continue to support the growing concept that EdAG, an underrecognized phase II metabolite of busulfan, plays a role in untoward cellular toxicities during busulfan pharmacotherapy.

Dienone Compounds: Targets and Pharmacological Responses

The biological responses to dienone compounds with a 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore have been studied extensively. Despite their expected general thiol reactivity, these compounds display considerable degrees of tumor cell selectivity. Here we review in vitro and preclinical studies of dienone compounds including b-AP15, VLX1570, RA-9, RA-190, EF24, HO-3867, and MCB-613. A common property of these compounds is their targeting of the ubiquitin–proteasome system (UPS), known to be essential for the viability of tumor cells. Gene expression profiling experiments have shown induction of responses characteristic of UPS inhibition, and experiments using cellular reporter proteins have shown that proteasome inhibition is associated with cell death. Other mechanisms of action such as reactivation of mutant p53, stimulation of steroid receptor coactivators, and induction of protein cross-linking have also been described. Although unsuitable as biological probes due to widespread reactivity, dienone compounds are cytotoxic to apoptosis-resistant tumor cells and show activity in animal tumor models.

Formation of trisubstituted buta-1,3-dienes and α,β-unsaturated ketones via the reaction of functionalized vinyl phosphates and vinyl phosphordiamidates with organometallic reagents

We studied the reactions of vinyl phosphates and vinyl phosphordiamidates containing an ester functional group with organometallic reagents. We found that the functionalized vinyl phosphates were smoothly converted into tri- and tetrasubstituted buta-1,3-dienes via the reaction with aryllithium reagents. Moreover, the vinyl phosphordiamidates were converted into α,β-unsaturated ketones using Grignard reagents. Based on the performed experiments, we proposed a reaction mechanism, which was confirmed by means of the isolation of key intermediates.

We studied the reactions of vinyl phosphates and vinyl phosphordiamidates containing an ester functional group with organometallic reagents.