Intein-mediated temperature control for complete biosynthesis of sanguinarine and its halogenated derivatives in yeast.

While sanguinarine has gained recognition for antimicrobial and antineoplastic activities, its complex conjugated structure and low abundance in plants impede broad applications. Here, we demonstrate the complete biosynthesis of sanguinarine and halogenated derivatives using highly engineered yeast strains. To overcome sanguinarine cytotoxicity, we establish a splicing intein-mediated temperature-responsive gene expression system (SIMTeGES), a simple strategy that decouples cell growth from product synthesis without sacrificing protein activity. To debottleneck sanguinarine biosynthesis, we identify two reticuline oxidases and facilitated functional expression of flavoproteins and cytochrome P450 enzymes via protein molecular engineering. After comprehensive metabolic engineering, we report the production of sanguinarine at a titer of 448.64 mg L-1. Additionally, our engineered strain enables the biosynthesis of fluorinated sanguinarine, showcasing the biotransformation of halogenated derivatives through more than 15 biocatalytic steps. This work serves as a blueprint for utilizing yeast as a scalable platform for biomanufacturing diverse benzylisoquinoline alkaloids and derivatives.

Maramycin, a Cytotoxic Isoquinolinequinone Terpenoid Produced through Heterologous Expression of a Bifunctional Indole Prenyltransferase/Tryptophan Indole-Lyase in S. albidoflavus.

Isoquinolinequinones represent an important family of natural alkaloids with profound biological activities. Heterologous expression of a rare bifunctional indole prenyltransferase/tryptophan indole-lyase enzyme from Streptomyces mirabilis P8-A2 in S. albidoflavus J1074 led to the activation of a putative isoquinolinequinone biosynthetic gene cluster and production of a novel isoquinolinequinone alkaloid, named maramycin (1). The structure of maramycin was determined by analysis of spectroscopic (1D/2D NMR) and MS spectrometric data. The prevalence of this bifunctional biosynthetic enzyme was explored and found to be a recent evolutionary event with only a few representatives in nature. Maramycin exhibited moderate cytotoxicity against human prostate cancer cell lines, LNCaP and C4-2B. The discovery of maramycin (1) enriched the chemical diversity of natural isoquinolinequinones and also provided new insights into crosstalk between the host biosynthetic genes and the heterologous biosynthetic genes in generating new chemical scaffolds.

Variability of Isoquinoline Alkaloid Profiles and Anticholinesterase Activities with Binding-Mode Predictions of Glaucium flavum Population.

In this study, phytochemical and biological activity studies supported by docking were carried out on a species of the genus Glaucium, a repository of isoquinoline alkaloids. The GC-MS (Gas Chromatography-Mass Spectrometry) method is used to characterize the isoquinoline alkaloids of Glaucium flavum Crantz. (Papaveraceae). G. flavum was collected from seven different regions of Türkiye (Antalya, Urla-Izmir, Mordogan-Izmir, Mugla, Assos-Canakkale, Karabiga-Canakkale, Giresun) and totally 17 compounds were detected by GC-MS. Glaucine was found to be the major constituent in the sample collected from Mugla, whereas isocorydine was recorded to be the principal alkaloid in other samples. Further fractionation studies on G. flavum collected from Antalya province in Southwestern Türkiye, yielded five major alkaloids (isocorydine 1, dihydrosanguinarine 2, glaucine 3, dehydroglaucine 4, protopine 5) which were characterized by spectroscopic methods. Anticholinesterase activities of the extracts and isolated alkaloids were also tested by in vitro Ellman method. The isolated compounds were also analyzed by a molecular docking technique to determine the binding orientations in the gorge of the active site of acetylcholinesterase (AChE) and a homology model of butyrylcholinesterase (BuChE). This is the first comparative investigation of the phytochemical composition and biodiversity of Glaucium flavum species growing in Türkiye.

Sal synthase induced cytotoxicity of PC12 cells through production of the dopamine metabolites salsolinol and N-methyl-salsolinol.

As a catechol isoquinoline, salsolinol (Sal) is widely distributed in mammalian brains, and is increased in the cerebrospinal fluid (CSF) and urine of Parkinsonian patients. Sal can be metabolized to N-methyl-salsolinol (NM-Sal), an MPP+-like neurotoxin, and impairs the function of dopaminergic neurons, causing the clinical symptoms of Parkinson's disease (PD). Sal synthase, which catalyzes the production of Sal from dopamine and acetaldehyde, may be the important enzyme in the metabolism of catechol isoquinolines (CTIQs). Previously, our work demonstrated the existence of Sal synthase in rat brain and identified its amino acid sequence. However, the biological function of Sal synthase has not been thoroughly explored, especially its role in dopaminergic neuronal degeneration. In this study, we tried to clarify the catalytic role of Sal synthase in the formation of CTIQs which are endogenous neurotoxins in the mammalian brain. Furthermore, the cytotoxicity of Sal synthase was also observed in dopaminergic PC12 cells. The results demonstrated that Sal synthase overexpression can increase the level of Sal and NM-Sal, and ultimately cause mitochondria damage and apoptosis.

Novel Biosynthetic Route to the Isoquinoline Scaffold.

Isoquinoline alkaloids are a large class of natural products with a broad range of biological activities, including antimicrobial, antitumor, antileukemic and anti-inflammatory properties. Although mostly found in plants, isoquinolines can also be found in the extracts of bacterial and fungal cultures. Regardless of the origin, most of the reported biosynthetic routes for isoquinolines use tyrosine as a main biosynthetic precursor. Here, we report the identification of a new biosynthetic pathway for production of isoquinolinequinone alkaloid mansouramycin D in Streptomyces albus Del14. Using feeding, mass spectrometry, and nuclear magnetic resonance spectroscopy, we demonstrate that tryptophan serves instead of tyrosine as a main mansouramycin biosynthetic precursor. The biosynthetic genes were identified in the chromosome of the strain by using gene inactivation and heterologous expression. Insights into the biosynthesis of mansouramycins are also presented.

Esterification promotes the intracellular accumulation of roxadustat, an activator of hypoxia-inducible factors, to extend its effective duration.

Kidney injury often causes anemia due to a lack of production of the erythroid growth factor erythropoietin (EPO) in the kidneys. Roxadustat is one of the first oral medicines inducing EPO production in patients with renal anemia by activating hypoxia-inducible factors (HIFs), which are activators of EPO gene expression. In this study, to develop prodrugs of roxadustat with improved permeability through cell membrane, we investigated the effects of 8 types of esterification on the pharmacokinetics and bioactivity of roxadustat using Hep3B hepatoma cells that HIF-dependently produce EPO. Mass spectrometry of cells incubated with the esterified roxadustat derivatives revealed that the designed compounds were deesterified after being taken up by cells and showed low cytotoxicity compared to the original compound. Esterification prolonged the effective duration of roxadustat with respect to EPO gene induction and HIF activation in cells transiently exposed to the compounds. In the kidneys and livers of mice, both of which are unique sites of EPO production, a majority of the methyl-esterified roxadustat was deesterified within 6 h after drug administration. The deesterified roxadustat derivative was continuously detectable in plasma and urine for at least 48 h after administration, while the administered compound became undetectable 24 h after administration. Additionally, we confirmed that methyl-esterified roxadustat activated erythropoiesis in mice by inducing Epo mRNA expression exclusively in renal interstitial cells, which have intrinsic EPO-producing potential. These data suggest that esterification could lead to the development of roxadustat prodrugs with improvements in cell membrane permeability, effective duration and cytotoxicity.

Complete biosynthesis of the bisbenzylisoquinoline alkaloids guattegaumerine and berbamunine in yeast.

Benzylisoquinoline alkaloids (BIAs) are a diverse class of medicinal plant natural products. Nearly 500 dimeric bisbenzylisoquinoline alkaloids (bisBIAs), produced by the coupling of two BIA monomers, have been characterized and display a range of pharmacological properties, including anti-inflammatory, antitumor, and antiarrhythmic activities. In recent years, microbial platforms have been engineered to produce several classes of BIAs, which are rare or difficult to obtain from natural plant hosts, including protoberberines, morphinans, and phthalideisoquinolines. However, the heterologous biosyntheses of bisBIAs have thus far been largely unexplored. Here, we describe the engineering of yeast strains that produce the Type I bisBIAs guattegaumerine and berbamunine de novo. Through strain engineering, protein engineering, and optimization of growth conditions, a 10,000-fold improvement in the production of guattegaumerine, the major bisBIA pathway product, was observed. By replacing the cytochrome P450 used in the final coupling reaction with a chimeric variant, the product profile was inverted to instead produce solely berbamunine. Our highest titer engineered yeast strains produced 108 and 25 mg/L of guattegaumerine and berbamunine, respectively. Finally, the inclusion of two additional putative BIA biosynthesis enzymes, SiCNMT2 and NnOMT5, into our bisBIA biosynthetic strains enabled the production of two derivatives of bisBIA pathway intermediates de novo: magnocurarine and armepavine. The de novo heterologous biosyntheses of bisBIAs presented here provide the foundation for the production of additional medicinal bisBIAs in yeast.

Reductive inactivation of the hemiaminal pharmacophore for resistance against tetrahydroisoquinoline antibiotics.

Antibiotic resistance is becoming one of the major crises, among which hydrolysis reaction is widely employed by bacteria to destroy the reactive pharmacophore. Correspondingly, antibiotic producer has canonically co-evolved this approach with the biosynthetic capability for self-resistance. Here we discover a self-defense strategy featuring with reductive inactivation of hemiaminal pharmacophore by short-chain dehydrogenases/reductases (SDRs) NapW and homW, which are integrated with the naphthyridinomycin biosynthetic pathway. We determine the crystal structure of NapW·NADPH complex and propose a catalytic mechanism by molecular dynamics simulation analysis. Additionally, a similar detoxification strategy is identified in the biosynthesis of saframycin A, another member of tetrahydroisoquinoline (THIQ) antibiotics. Remarkably, similar SDRs are widely spread in bacteria and able to inactive other THIQ members including the clinical anticancer drug, ET-743. These findings not only fill in the missing intracellular events of temporal-spatial shielding mode for cryptic self-resistance during THIQs biosynthesis, but also exhibit a sophisticated damage-control in secondary metabolism and general immunity toward this family of antibiotics.

The Effect of Single Nucleotide Variations in the Transmembrane Domain of OATP1B1 on in vitro Functionality.

PURPOSE: Organic Anion Transporting Polypeptide 1B1 (OATP1B1) mediates hepatic influx and clearance of many drugs, including statins. The SLCO1B1 gene is highly polymorphic and its function-impairing variants can predispose patients to adverse effects. The effects of rare genetic variants of SLCO1B1 are mainly unexplored. We examined the impact of eight naturally occurring rare variants and the well-known SLCO1B1 c.521C > T (V174A) variant on in vitro transport activity, cellular localization and abundance. METHODS: Transport of rosuvastatin and 2,7-dichlorofluorescein (DCF) in OATP1B1 expressing HEK293 cells was measured to assess changes in activity of the variants. Immunofluorescence and confocal microscopy determined the cellular localization of OATP1B1 and LC-MS/MS based quantitative targeted absolute proteomics analysis quantified the amount of OATP1B1 in crude membrane fractions. RESULTS: All studied variants, with the exception of P336R, reduced protein abundance to varying degree. V174A reduced protein abundance the most, over 90% compared to wild type. Transport function was lost in G76E, V174A, L193R and R580Q variants. R181C decreased activity significantly, while T345M and L543W retained most of wild type OATP1B1 activity. P336R showed increased activity and H575L decreased the transport of DCF significantly, but not of rosuvastatin. Decreased activity was interrelated with lower absolute protein abundance in the studied variants. CONCLUSIONS: Transmembrane helices 2, 4 and 11 appear to be crucial for proper membrane localization and function of OATP1B1. Four of the studied variants were identified as loss-of-function variants and as such could make the individual harboring these variants susceptible to altered pharmacokinetics and adverse effects of substrate drugs.

Potential value and chemical characterization of gut microbiota derived nitrogen containing metabolites in feces from Periplaneta americana (L.) at different growth stages.

The American cockroach, Periplaneta americana (L.), is able to highly survive in various complicated environments around the globe, and often considered as a pest. In contrast, billions of P. americana have been massively reared in China and extensively used as a medicinal insect, due to its function for preventing and treating ulceration and heart failure. Considering the possibility that microbiota-derived metabolites could be an effective source to identify promising candidate drugs, we attempted to establish a rapid method for simultaneous determination of gut microbiota metabolites from medicinal insects. In this study, network pharmacology approach and ultra-performance liquid chromatography (UPLC) technique were employed to reveal the potential pharmacological activity and dynamics variation of nitrogen-containing metabolites (NCMs) originated from the gut microbiota of breeding P. americana at different growth stages. A metabolites-targets-diseases network showed that NCMs are likely to treat diseases such as ulceration and cancer. The analysis of NCMs' content with the growth pattern of P. americana indicated that the content of NCMs declined with P. americana aging. Both principal component analysis and orthogonal partial least squares discriminant analysis suggested that 8-hydroxy-2-quinolinecarboxylic acid and 8-hydroxy-3,4-dihydro-2(1H)-quinolinone are the potential differential metabolic markers for discriminating between nymphs and adults of P. americana. Moreover, the developed UPLC method showed an excellent linearity (R2 > 0.999), repeatability (RSD < 2.6%), intra- and inter-day precisions (RSD < 2.2%), and recovery (95.5%-99.0%). Collectively, the study provides a valuable strategy for analyzing gut microbiota metabolites from insects and demonstrates the prospects for discovering novel drug candidates from the feces of P. americana.

Roflumilast ameliorates cognitive deficits in a mouse model of amyloidogenesis and tauopathy: Involvement of nitric oxide status, Aß extrusion transporter ABCB1, and reversal by PKA inhibitor H89.

The biological cascade of second messenger-cyclic adenosine monophosphate (cAMP) -as a molecular mechanism implicated in memory and learning regulation has captured the attention of neuroscientists worldwide. cAMP triggers its foremost effector, protein kinase A (PKA), resulting in the activation of innumerable downstream targets. Roflumilast (ROF), a phosphodiesterase 4 inhibitor, has demonstrated a greater efficiency in enhancing cAMP signaling in various neurological disorders. This study was conducted to identify various downstream targets of PKA as mechanistic tools through which ROF could hinder the progressive cognitive impairment following central streptozotocin (STZ) administration in mice. Animals were injected with STZ (3 mg/kg/i.c.v) once. Five hours later, mice received ROF (0.4 mg/kg) with or without the PKA inhibitor, H89, for 21 days. ROF highly preserved the structure of hippocampal neurons. It improved the ability of mice to develop short-term memories and retrieve spatial memories in Y-maze and Morris water maze tests, respectively. ROF enhanced the gene expression of ABCB1 transporters and pregnane X receptors (PXR), and hampered Aß accumulation in hippocampus. Simultaneously, it interfered with the processes of tau phosphorylation and nitration. This effect was associated with an upsurge in hippocampal arginase activity as well as a decline in glycogen synthase kinase-3ß activity, nitric oxide synthase (NOS) activity, and inducible NOS expression. Contrariwise, ROF's beneficial effects were utterly abolished by co-administration of H89. In conclusion, boosting PKA, by ROF, modulated PXR/ABCB1 expression and arginase/NOS activities to restrict the main post-translational modifications of tau, Aß deposition and, accordingly, cognitive deterioration of sporadic Alzheimer's disease.

Modelling and Phenotypic Screening of NAP-6 and 10-Cl-BBQ, AhR Ligands Displaying Selective Breast Cancer Cytotoxicity in Vitro.

To exploit the interaction of the aryl hydrocarbon receptor (AhR) pathway in developing breast-cancer-specific cytotoxic compounds, we examined the breast cancer selectivity and the docking pose of the AhR ligands (Z)-2-(2-aminophenyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (NAP-6; 5) and 10-chloro-7H-benzo[de]benzo[4,5]imidazo[2,1-a]isoquinolin-7-one (10-Cl-BBQ; 6). While the breast cancer selectivity of 5 in vitro is known, we discuss the SAR around this lead and, by using phenotypic cell-line screening and the MTT assay, show for the first time that 6 also presents with breast cancer selectivity, notably in the triple-negative (TN) receptor breast cancer cell line MDA-MB-468, the ER+ breast cancer cell lines T47D, ZR-75-1 and the HER2+ breast cancer cell line SKBR3 (GI50 values of 0.098, 0.97, 0.13 and 0.21 µM, respectively). Indeed, 6 is 55 times more potent in MDA-MB-468 cells than normal MCF10A breast cells (GI50 of 0.098 vs 5.4 µM) and more than 130 times more potent than in cell lines derived from pancreas, brain and prostate (GI50 of 0.098 vs 10-13 µM). Molecular docking poses of 5 and 6 together with analogue synthesis and phenotypic screening show the importance of the naphthalene moiety, and an ortho-disposed substituent on the N-phenyl moiety for biological activity.

Optimizations of a novel fluorescence polarization-based high-throughput screening assay for ß-catenin/LEF1 interaction inhibitors.

Aberrant activation of the Wnt/ß-catenin signaling pathway is prominent in the development and metastasis of non-small cell lung cancer (NSCLC). Highly effective inhibition of this pathway highlights a therapeutic avenue against NSCLC. Moreover, ß-catenin/LEF1 interaction regulates ß-catenin nuclear transport as well as the transcriptions of the key oncogenes in Wnt/ß-catenin signaling pathway. Therefore, interruption of this interaction would be a promising therapeutic strategy for NSCLC metastasis. To date, no economical and rapid high-throughput screening (HTS) assay has been reported for the discovery of ß-catenin/LEF1 interaction inhibitors. In this study, we developed a novel fluorescence polarization (FP)-based HTS assay to identify ß-catenin/LEF1 interaction inhibitors. The FITC-LEF1 sequence, incubation time, temperature, and DMSO resistance were optimized, and then a high Z' factor of 0.77 was achieved. A pilot screening of a natural product library via this established FP screening assay identified sanguinarine analogues as potential ß-catenin/LEF1 interaction inhibitors. GST pull-down and surface plasmon resonance (SPR) assay demonstrated that ß-catenin/LEF1 interaction is a potential anticancer target of sanguinarine in vitro. This newly developed FP screening assay will be vital for the rapid discovery of novel Wnt inhibitors targeting ß-catenin/LEF1 interaction.

N-(Pyrimidin-2-yl)-1,2,3,4-tetrahydroisoquinolin-6-amine Derivatives as Selective Janus Kinase 2 Inhibitors for the Treatment of Myeloproliferative Neoplasms.

In this study, we described a series of N-(pyrimidin-2-yl)-1,2,3,4-tetrahydroisoquinolin-6-amine derivatives as selective JAK2 (Janus kinase 2) inhibitors. Systematic exploration of the structure-activity relationship though cyclization modification based on previously reported compound 18e led to the discovery of the superior derivative 13ac. Compound 13ac showed excellent potency on JAK2 kinase, SET-2, and Ba/F3V617F cells (high expression of JAK2V617F mutation) with IC50 values of 3, 11.7, and 41 nM, respectively. Further mechanistic studies demonstrated that compound 13ac could downregulate the phosphorylation of downstream proteins of JAK2 kinase in cells. Compound 13ac also showed good selectivity in kinase scanning and potent in vivo antitumor efficacy with 82.3% tumor growth inhibition in the SET-2 xenograft model. Moreover, 13ac significantly ameliorated the disease symptoms in a Ba/F3-JAK2V617F allograft model, with 77.1% normalization of spleen weight, which was more potent than Ruxolitinib.

Structure-Based Drug Design of Bisubstrate Inhibitors of Phenylethanolamine N-Methyltransferase Possessing Low Nanomolar Affinity at Both Substrate Binding Domains1.

The enzyme phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1.28) catalyzes the final step in the biosynthesis of epinephrine and is a potential drug target, primarily for the control of hypertension. Unfortunately, many potent PNMT inhibitors also possess significant affinity for the a2-adrenoceptor, which complicates the interpretation of their pharmacology. A bisubstrate analogue approach offers the potential for development of highly selective inhibitors of PNMT. This paper documents the design, synthesis, and evaluation of such analogues, several of which were found to possess human PNMT (hPNMT) inhibitory potency <5 nM versus AdoMet. Site-directed mutagenesis studies were consistent with bisubstrate binding. Two of these compounds (19 and 29) were co-crystallized with hPNMT and the resulting structures revealed both compounds bound as predicted, simultaneously occupying both substrate binding domains. This bisubstrate inhibitor approach has resulted in one of the most potent (20) and selective (vs the a2-adrenoceptor) inhibitors of hPNMT yet reported.

Antagonists of the serotonin receptor 5A target human breast tumor initiating cells.

BACKGROUND: Breast tumor initiating cells (BTIC) are stem-like cells that initiate and sustain tumor growth, and drive disease recurrence. Identifying therapies targeting BTIC has been hindered due primarily to their scarcity in tumors. We previously reported that BTIC frequency ranges between 15% and 50% in multiple mammary tumors of 3 different transgenic mouse models of breast cancer and that this frequency is maintained in tumor cell populations cultured in serum-free, chemically defined media as non-adherent tumorspheres. The latter enabled high-throughput screening of small molecules for their capacity to affect BTIC survival. Antagonists of several serotonin receptors (5-HTRs) were among the hit compounds. The most potent compound we identified, SB-699551, selectively binds to 5-HT5A, a Gαi/o protein coupled receptor (GPCR). METHODS: We evaluated the activity of structurally unrelated selective 5-HT5A antagonists using multiple orthogonal assays of BTIC frequency. Thereafter we used a phosphoproteomic approach to uncover the mechanism of action of SB-699551. To validate the molecular target of the antagonists, we used the CRISPR-Cas9 gene editing technology to conditionally knockout HTR5A in a breast tumor cell line. RESULTS: We found that selective antagonists of 5-HT5A reduced the frequency of tumorsphere initiating cells residing in breast tumor cell lines and those of patient-derived xenografts (PDXs) that we established. The most potent compound among those tested, SB-699551, reduced the frequency of BTIC in ex vivo assays and acted in concert with chemotherapy to shrink human breast tumor xenografts in vivo. Our phosphoproteomic experiments established that exposure of breast tumor cells to SB-699551 elicited signaling changes in the canonical Gαi/o-coupled pathway and the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) axis. Moreover, conditional mutation of the HTR5A gene resulted in the loss of tumorsphere initiating cells and BTIC thus mimicking the effect of SB-699551. CONCLUSIONS: Our data provide genetic, pharmacological and phosphoproteomic evidence consistent with the on-target activity of SB-699551. The use of such agents in combination with cytotoxic chemotherapy provides a novel therapeutic approach to treat breast cancer.

Structural Insights into PROTAC-Mediated Degradation of Bcl-xL.

The Bcl-2 family of proteins, such as Bcl-xL and Bcl-2, play key roles in cancer cell survival. Structural studies of Bcl-xL formed the foundation for the development of the first Bcl-2 family inhibitors and FDA approved drugs. Recently, Proteolysis Targeting Chimeras (PROTACs) that degrade Bcl-xL have been proposed as a therapeutic modality with the potential to enhance potency and reduce toxicity versus antagonists. However, no ternary complex structures of Bcl-xL with a PROTAC and an E3 ligase have been successfully determined to guide this approach. Herein, we report the design, characterization, and X-ray structure of a VHL E3 ligase-recruiting Bcl-xL PROTAC degrader. The 1.9 Å heterotetrameric structure, composed of (ElonginB:ElonginC:VHL):PROTAC:Bcl-xL, reveals an extensive network of neo-interactions, between the E3 ligase and the target protein, and between noncognate parts of the PROTAC and partner proteins. This work illustrates the challenges associated with the rational design of bifunctional molecules where interactions involve composite interfaces.

Novel Fredericamycin Variant Overproduced by a Streptomycin-resistant Streptomyces albus subsp. chlorinus Strain.

Streptomycetes are an important source of natural products potentially applicable in the pharmaceutical industry. Many of these drugs are secondary metabolites whose biosynthetic genes are very often poorly expressed under laboratory cultivation conditions. In many cases, antibiotic-resistant mutants exhibit increased production of natural drugs, which facilitates the identification and isolation of new substances. In this study, we report the induction of a type II polyketide synthase gene cluster in the marine strain Streptomyces albus subsp. chlorinus through the selection of streptomycin-resistant mutants, resulting in overproduction of the novel compound fredericamycin C2 (1). Fredericamycin C2 (1) is structurally related to the potent antitumor drug lead fredericamycin A.

Biosynthesis, synthetic studies, and biological activities of the jadomycin alkaloids and related analogues.

The jadomycins are an expanding class of compounds produced from Streptomyces venezuelae, by diverting the normal biosynthesis which provides the antibiotic chloramphenicol. In the presence of amino acids, and either by heat shock, supplementation with ethanol, or when phage SV1 is added to the culture, the formation of substituted jadomycins and benzo[b]phenanthridines can be achieved. The first part of this review provides details of intermediates involved in the biosynthesis of the jadomycins and the related benzo[b]phenanthridines. Both the jadomycins and the benzo[b]phenanthridines share biosynthetic pathways with a large class of naturally occurring compounds known as the angucyclines. The biosynthetic pathways diverge when it is postulated that an intermediate quinone, such as 3-(2-formyl-6-hydroxy-4-methylphenyl)-8-hydroxy-1,4-naphthoquinone-2-carboxylic acid is formed. The quinone then undergoes reactions with amino acids and derivatives in the culture medium to ultimately afford a library of jadomycins and a few benzo[b]phenanthridines. The second part of the review initially details synthetic efforts toward the synthesis of the naturally occurring benzo[b]phenanthridine, phenanthroviridin, and then outlines methods that have been used to assemble a selection of jadomycins. Total syntheses of jadomycin A and B, derived from l-isoleucine, are described. In addition, the synthesis of the aglycon of jadomycins M, W, S, and T is outlined. These four jadomycins were derived from l-methionine, l-tryptophan, l-serine and l-threonine respectively. As a result of these synthetic efforts, the structures of jadomycin S and T have been revised. The third part of the review describes the reported antibacterial and anticancer activities of both the jadomycins and some naturally occurring benzo[b]phenanthridines.

Discovery of Potent Inhibitors against P-Glycoprotein-Mediated Multidrug Resistance Aided by Late-Stage Functionalization of a 2-(4-(Pyridin-2-yl)phenoxy)pyridine Analogue.

SIS3 is a specific inhibitor of Smad3 that inhibits the TGFß1-induced phosphorylation of Smad3. In this article, a variety of SIS3 derivatives were designed and synthesized to discover potential inhibitors against P-glycoprotein-mediated multidrug resistance aided by late-stage functionalization of a 2-(4-(pyridin-2-yl)phenoxy)pyridine analogue. A novel class of potent P-gp reversal agents were investigated, and a lead compound 37 was identified as a potent P-gp reversal agent with strong bioactivity and outstanding affinity for P-gp.