Prebiotic Syntheses of Organophosphorus Compounds from Reduced Source of Phosphorus in Non-Aqueous Solvents

Reduced-oxidation-state phosphorus (reduced P, hereafter) compounds were likely available on the early Earth via meteorites or through various geologic processes. Due to their reactivity and high solubility, these compounds could have played a significant role in the origin of various organophosphorus compounds of biochemical significance. In the present work, we study the reactions between reduced P compounds and their oxidation products, with the three nucleosides (uridine, adenosine, and cytidine), with organic alcohols (glycerol and ethanolamine), and with the tertiary ammonium organic compound, choline chloride. These reactions were studied in the non-aqueous solvent formamide and in a semi-aqueous solvent comprised of urea: ammonium formate: water (UAFW, hereafter) at temperatures of 55-68 °C. The inorganic P compounds generated through Fenton chemistry readily dissolve in the non-aqueous and semi-aqueous solvents and react with organics to form organophosphites and organophosphates, including those which are identified as phosphate diesters. This dual approach (1) use of non-aqueous and semi-aqueous solvents and (2) use of a reactive inorganic P source to promote phosphorylation and phosphonylation reactions of organics readily promoted anhydrous chemistry and condensation reactions, without requiring any additive, catalyst, or other promoting agent under mild heating conditions. We also present a comparative study of the release of P from various prebiotically relevant phosphate minerals and phosphite salts (e.g., vivianite, apatite, and phosphites of iron and calcium) into formamide and UAFW. These results have direct implications for the origin of biological P compounds from non-aqueous solvents of prebiotic provenance.

Rational Design of Sulfonyl-γ-AApeptides as Highly Potent HIV-1 Fusion Inhibitors with Broad-Spectrum Activity

The HIV-1 epidemic has significant social and economic implications for public health. Developing new antivirus drugs to eradicate drug resistance is still urgently needed. Herein, we demonstrated that sulfonyl-γ-AApeptides could be designed to mimic MTSC22EK, one potent HIV fusion inhibitor derived from CHR. The best two sequences revealed comparable activity to MTSC22EK in an authentic HIV-1 infection assay and exhibited broad-spectrum anti-HIV-1 activity to many HIV-1 clinical isolates. Furthermore, sulfonyl-γ-AApeptides show remarkable resistance to proteolysis and favorable permeability in PAMPA-GIT and PAMPA-BBB assays, suggesting that both sequences could control HIV-1 within the central nervous system and possess promising oral bioavailability. Mechanistic investigations suggest that these sulfonyl-γ-AApeptides function by mimicking the CHR of gp41 and tightly bind with NHR, thereby inhibiting the formation of the 6-HB structure necessary for HIV-1 fusion. Overall, our results suggest that sulfonyl-γ-AApeptides represent a new generation of anti-HIV-1 fusion inhibitors. Moreover, this design strategy could be adopted to modulate many of the PPIs.

Inhibition of Hypoxia-Inducible Transcription Factor (HIF-1α) Signaling with Sulfonyl-γ-AApeptide Helices

The development of inhibitors that selectively block protein-protein interactions (PPIs) is crucial for chemical biology, medicinal chemistry, and biomedical sciences. Herein, we reported the design, synthesis, and investigation of sulfonyl-γ-AApeptide as an alternative strategy of canonical peptide-based inhibitors to disrupt hypoxia-inducible factor 1α (HIF-1α) and p300 PPI by mimicking the helical domain of HIF-1α involved in the binding to p300. The designed molecules recognized the p300 protein with high affinity and potently inhibited the hypoxia-inducible signaling pathway. Gene expression profiling supported the idea that the lead molecules selectively inhibited hypoxia-inducible genes involved in the signaling cascade. Our studies also demonstrated that both helical faces consisting of either chiral side chains or achiral sulfonyl side chains of sulfonyl-γ-AApeptides could be adopted for mimicry of the α-helix engaging in PPIs. Furthermore, these sulfonyl-γ-AApeptides were cell-permeable and exhibited favorable stability and pharmacokinetic profiles. Our results could inspire the design of helical sulfonyl-γ-AApeptides as a general strategy to mimic the protein helical domain and modulate many other PPIs.

An HR2-Mimicking Sulfonyl-γ-AApeptide Is a Potent Pan-coronavirus Fusion Inhibitor with Strong Blood-Brain Barrier Permeability, Long Half-Life, and Promising Oral Bioavailability

Neutralizing antibodies and fusion inhibitory peptides have the potential required to combat the global pandemic caused by SARS-CoV-2 and its variants. However, the lack of oral bioavailability and enzymatic susceptibility limited their application, necessitating the development of novel pan-CoV fusion inhibitors. Herein we report a series of helical peptidomimetics, d-sulfonyl-γ-AApeptides, which effectively mimic the key residues of heptad repeat 2 and interact with heptad repeat 1 in the SARS-CoV-2 S2 subunit, resulting in inhibiting SARS-CoV-2 spike protein-mediated fusion between virus and cell membranes. The leads also displayed broad-spectrum inhibitory activity against a panel of other human CoVs and showed strong potency in vitro and in vivo. Meanwhile, they also demonstrated complete resistance to proteolytic enzymes or human sera and exhibited extremely long half-life in vivo and highly promising oral bioavailability, delineating their potential as pan-CoV fusion inhibitors with the potential to combat SARS-CoV-2 and its variants.

Development of the Safe and Broad-Spectrum Aldehyde and Ketoamide Mpro inhibitors Derived from the Constrained α, γ-AA Peptide Scaffold

SARS-CoV-2 is still wreaking havoc all over the world with surging morbidity and high mortality. The main protease (Mpro) is essential in the replication of SARS-CoV-2, enabling itself an active target for antiviral development. Herein, we reported the design and synthesis of a new class of peptidomimetics-constrained α, γ-AApeptides, based on which a series of aldehyde and ketoamide inhibitors of the Mpro of SARS-CoV-2 were prepared. The lead compounds showed excellent inhibitory activity in the FRET-based Mpro enzymatic assay not only for the Mpro of SARS-CoV-2 but also for SARS-CoV and MERS-CoV, along with HCoVs like HCoV-OC43, HCoV-229E, HCoV-NL63 and HKU1. The X-ray crystallographic results demonstrated that our compounds form a covalent bond with the catalytic Cys145. They also demonstrated effective antiviral activity against live SARS-CoV-2. Overall, the results suggest that α, γ-AApeptide could be a promising molecular scaffold in designing novel Mpro inhibitors of SARS-CoV-2 and other coronaviruses.

Discovery of Cyclic Peptidomimetic Ligands Targeting the Extracellular Domain of EGFR

It is very promising to target the extracellular domain of epidermal growth factor receptor (EGFR) for developing novel and selective anticancer therapies. Herein, we report the discovery of a novel small molecule, M-2-5, from a one-bead-two-compound (OBTC) cyclic γ-AApeptide library. The molecule was found to bind tightly to the extracellular domain of EGFR. Intriguingly, this molecule could also effectively antagonize EGF-stimulated EGFR phosphorylation and downstream signal transduction. Furthermore, together with its remarkable resistance to proteolytic degradation, M-2-5 was shown to effectively inhibit cell proliferation and migration in vitro and suppresses the growth of tumor in the A549 xenograft model in vivo, highlighting its potential therapeutic application for cancer treatment.

In vitro and in vivo cardiac toxicity of flavored electronic nicotine delivery systems

The usage of flavored electronic nicotine delivery systems (ENDS) is popular, specifically in the teen and young adult age-groups. The possible cardiac toxicity of the flavoring aspect of ENDS is largely unknown. Vaping, a form of electronic nicotine delivery, uses "e-liquid" to generate "e-vapor," an aerosolized mixture of nicotine and/or flavors. We report our investigation into the cardiotoxic effects of flavored e-liquids. E-vapors containing flavoring aldehydes such as vanillin and cinnamaldehyde, as indicated by mass spectrometry, were more toxic in HL-1 cardiomyocytes than fruit-flavored e-vapor. Exposure of human induced pluripotent stem cell-derived cardiomyocytes to cinnamaldehyde or vanillin-flavored e-vapor affected the beating frequency and prolonged the field potential duration of these cells more than fruit-flavored e-vapor. In addition, vanillin aldehyde-flavored e-vapor reduced the human ether-à-go-go-related gene (hERG)-encoded potassium current in transfected human embryonic kidney cells. In mice, inhalation exposure to vanillin aldehyde-flavored e-vapor for 10 wk caused increased sympathetic predominance in heart rate variability measurements. In vivo inducible ventricular tachycardia was significantly longer, and in optical mapping, the magnitude of ventricular action potential duration alternans was significantly larger in the vanillin aldehyde-flavored e-vapor-exposed mice than in controls. We conclude that the widely popular flavored ENDS are not harm free, and they have a potential for cardiac harm. More studies are needed to further assess their cardiac safety profile and long-term health effects.NEW & NOTEWORTHY The use of electronic nicotine delivery systems (ENDS) is not harm free. It is not known whether ENDS negatively affect cardiac electrophysiological function. Our study in cell lines and in mice shows that ENDS can compromise cardiac electrophysiology, leading to action potential instability and inducible ventricular arrhythmias. Further investigations are necessary to assess the long-term cardiac safety profile of ENDS products in humans and to better understand how individual components of ENDS affect cardiac toxicity.

ent-Labdane Diterpenoids from the Aerial Parts of Eupatorium obtusissmum

Six new ent-labdane diterpenoids, uasdlabdanes A-F (1-6), were isolated from the aerial parts of Eupatorium obtusissmum. The new structures were elucidated through spectroscopic and spectrometric data analyses. The absolute configurations of compounds 1 and 2 were established by X-ray crystallography, and those of 3-6, by comparison of experimental and calculated electronic circular dichroism spectra. The antiproliferative activity of the compounds was studied in a panel of six representative human solid tumor cell lines and showed GI50 values ranging from 19 to >100 μM.

Synthesis, stereochemical analysis, and derivatization of myricanol provide new probes that promote autophagic tau clearance

We previously discovered that one specific scalemic preparation of myricanol (1), a constituent of Myrica cerifera (bayberry/southern wax myrtle) root bark, could lower the levels of the microtubule-associated protein tau (MAPT). The significance is that tau accumulates in a number of neurodegenerative diseases, the most common being Alzheimer's disease (AD). Herein, a new synthetic route to prepare myricanol using a suitable boronic acid pinacol ester intermediate is reported. An X-ray crystal structure of the isolated myricanol (1) was obtained and showed a co-crystal consisting of (+)-aR,11S-myricanol (2) and (-)-aS,11R-myricanol (3) coformers. Surprisingly, 3, obtained from chiral separation from 1, reduced tau levels in both cultured cells and ex vivo brain slices from a mouse model of tauopathy at reasonable mid-to-low micromolar potency, whereas 2 did not. SILAC proteomics and cell assays revealed that 3 promoted tau degradation through an autophagic mechanism, which was in contrast to that of other tau-lowering compounds previously identified by our group. During the course of structure-activity relationship (SAR) development, we prepared compound 13 by acid-catalyzed dehydration of 1. 13 had undergone an unexpected structural rearrangement through the isomyricanol substitution pattern (e.g., 16), as verified by X-ray structural analysis. Compound 13 displayed robust tau-lowering activity, and, importantly, its enantiomers reduced tau levels similarly. Therefore, the semisynthetic analogue 13 provides a foundation for further development as a tau-lowering agent without its SAR being based on chirality.

Miniaturized Cultivation of Microbiota for Antimalarial Drug Discovery

The ongoing search for effective antiplasmodial agents remains essential in the fight against malaria worldwide. Emerging parasitic drug resistance places an urgent need to explore chemotherapies with novel structures and mechanisms of action. Natural products have historically provided effective antimalarial drug scaffolds. In an effort to search nature's chemical potential for antiplasmodial agents, unconventionally sourced organisms coupled with innovative cultivation techniques were utilized. Approximately 60,000 niche microbes from various habitats (slow-growing terrestrial fungi, Antarctic microbes, and mangrove endophytes) were cultivated on a small-scale, extracted, and used in high-throughput screening to determine antimalarial activity. About 1% of crude extracts were considered active and 6% partially active (≥ 67% inhibition at 5 and 50 μg/mL, respectively). Active extracts (685) were cultivated on a large-scale, fractionated, and screened for both antimalarial activity and cytotoxicity. High interest fractions (397) with an IC50 < 1.11 μg/mL were identified and subjected to chromatographic separation for compound characterization and dereplication. Identifying active compounds with nanomolar antimalarial activity coupled with a selectivity index tenfold higher was accomplished with two of the 52 compounds isolated. This microscale, high-throughput screening project for antiplasmodial agents is discussed in the context of current natural product drug discovery efforts.

Screening mangrove endophytic fungi for antimalarial natural products

We conducted a screening campaign to investigate fungi as a source for new antimalarial compounds. A subset of our fungal collection comprising Chinese mangrove endophytes provided over 5000 lipophilic extracts. We developed an accelerated discovery program based on small-scale cultivation for crude extract screening and a high-throughput malaria assay. Criteria for hits were developed and high priority hits were subjected to scale-up cultivation. Extracts from large scale cultivation were fractionated and these fractions subjected to both in vitro malaria and cytotoxicity screening. Criteria for advancing fractions to purification were developed, including the introduction of a selectivity index and by dereplication of known metabolites. From the Chinese mangrove endophytes, four new compounds (14–16, 18) were isolated including a new dimeric tetrahydroxanthone, dicerandrol D (14), which was found to display the most favorable bioactivity profile.

Corrigendum to: Structural Variations to the 9-N-Methyladeninium Diterpenoid Hybrid Commonly Isolated from Agelas Sponges

Four novel 9-N-methyladeninium diterpenoids, agelasine M (3), 2-oxo-agelasine B (4), gelasine A (5), and gelasine B (6) accompanied by the known-agelasine B (1) and F (2) were isolated from the marine sponge Agelas sp. collected in Papua New Guinea. Compounds 3?6 represent higher unsaturated 9-N-methyladeninium bicyclic diterpenoid derivatives including 5 and 6 as unusual norditerpenoid-agelasines. Their structures were elucidated through detailed physical data analyses and comparison with literature properties. All pure compounds were evaluated for inhibitory activity against Trypanosoma brucei as well as for cytotoxicity against Jurkat cells.

Additional insights on the bastadins: isolation of analogues from the sponge Ianthella cf. reticulata and exploration of the oxime configurations

The focus of this study is on the bastadin class of bromotyrosine derivatives, commonly isolated from Ianthella marine sponges, and is the first report on the secondary metabolites from Ianthella cf. reticulata. Two new bastadins were isolated, (E,Z)-bastadin 19 (1a), a diastereoisomer of the known (E,E)-bastadin 19 (1b), and dioxepine bastadin 3 (2), an unusual dibenzo-1,3-dioxepine. A bastadin NMR database was created and assisted in the structure determination of 1b and 2 and the rapid dereplication of 10 other known compounds including bastadins 2-9 (3-10), 13 (11), and 19 (1a). The geometry of the 2-(hydroxyimino)-N-alkylamide chains, a chemical feature present in all bastadins, was further probed, and new insights regarding the natural oxime configuration are discussed. Bastadins possessing (E,Z)-, (Z,E)-, or (E,E)-dioxime configurations could be artifacts of isolation or storage in solution. Therefore, this point was explored by photochemical and thermal isomerization studies, as well as molecular mechanics calculations. Bastadins 13 (11) and 19 (1a) exhibited moderate inhibition against Trypanosoma brucei, and bastadin 4 (5) was cytotoxic to HCT-116 colon cancer cells.

Structural Variations to the 9-N-Methyladeninium Diterpenoid Hybrid Commonly Isolated from Agelas Sponges

Four novel 9-N-methyladeninium diterpenoids, agelasine M (3), 2-oxo-agelasine B (4), gelasine A (5), and gelasine B (6) accompanied by the known-agelasine B (1) and F (2) were isolated from the marine sponge Agelas sp. collected in Papua New Guinea. Compounds 3–6 represent higher unsaturated 9-N-methyladeninium bicyclic diterpenoid derivatives including 5 and 6 as unusual norditerpenoid-agelasines. Their structures were elucidated through detailed physical data analyses and comparison with literature properties. All pure compounds were evaluated for inhibitory activity against Trypanosoma brucei as well as for cytotoxicity against Jurkat cells.

NMR strategy for unraveling structures of bioactive sponge-derived oxy-polyhalogenated diphenyl ethers

The overexpression of the Mcl-1 protein in cancerous cells results in the sequestering of Bak, a key component in the regulation of normal cell apoptosis. Our investigation of the ability of marine-derived small-molecule natural products to inhibit this protein-protein interaction led to the isolation of several bioactive oxy-polyhalogenated diphenyl ethers. A semipure extract, previously obtained from Dysidea (Lamellodysidea) herbacea and preserved in our repository, along with an untouched Dysidea granulosa marine sponge afforded 13 distinct oxy-polyhalogenated diphenyl ethers. Among these isolates were four new compounds, 5, 6, 10, and 12. The structure elucidation of these molecules was complicated by the plethora of structural variants that exist in the literature. During dereplication, we established a systematic method for analyzing this class of compounds. The strategy is governed by trends in the (1)H and (13)C NMR shifts of the aromatic rings, and the success of the strategy was checked by X-ray crystal structure analysis.