New Scaffold for Angiogenesis Inhibitors Discovered by Targeted Chemical Transformations of Wondonin Natural Products

Innovative medicinal chemistry strategies for enhancing drug solubility

Drug candidates with poor solubility have been recognized as the cause of many drug development failures, owing to the fact that low solubility is unfavorable for physicochemical, pharmacokinetic (PK) and pharmacodynamic (PD) properties. Given the imperative role of solubility during drug development, we herein summarize various strategies for solubility optimizations from a medicinal chemistry perspective, including introduction of polar group, salt formation, structural simplification, disruption of molecular planarity and symmetry, optimizations on the solvent exposed region as well as prodrug design. In addition, methods for solubility assessment and prediction are reviewed. Besides, we have deeply discussed the strategies for solubility improvement. This paper is expected to be beneficial for the development of drug-like molecules with good solubility.

Bioactive compounds isolated from the bark of Aesculus glabra Willd

The Aesculus genus has several species, most notably Aesculus hippocastanum, with reported cytotoxic and venotonic effects. The angiogenic effect from A. hippocastanum is of interest given the current limitations of anti-angiogenic therapeutics. Aesculus glabra (Willdenow), known as the Ohio Buckeye Tree is a species native to North America with reported medicinal use by the Native Americans. Previous phytochemical studies have focused on the seed and leaf contents of the glabra species, with most of them reporting cytotoxic activity. In this study, we assessed preliminary anti-angiogenic activity and toxicity of isolated compounds from the bark of A. glabra utilizing a zebrafish (Danio rerio) model. Procyanidin A2 and epicatechin, two pure isolates, were tested using zebrafish and gave an anti-angiogenic response, suggesting an underlying mechanism involved in vascular development.

Marine-Derived Leads as Anticancer Candidates by Disrupting Hypoxic Signaling through Hypoxia-Inducible Factors Inhibition

The inadequate vascularization seen in fast-growing solid tumors gives rise to hypoxic areas, fostering specific changes in gene expression that bolster tumor cell survival and metastasis, ultimately leading to unfavorable clinical prognoses across different cancer types. Hypoxia-inducible factors (HIF-1 and HIF-2) emerge as druggable pivotal players orchestrating tumor metastasis and angiogenesis, thus positioning them as prime targets for cancer treatment. A range of HIF inhibitors, notably natural compounds originating from marine organisms, exhibit encouraging anticancer properties, underscoring their significance as promising therapeutic options. Bioprospection of the marine environment is now a well-settled approach to the discovery and development of anticancer agents that might have their medicinal chemistry developed into clinical candidates. However, despite the massive increase in the number of marine natural products classified as 'anticancer leads,' most of which correspond to general cytotoxic agents, and only a few have been characterized regarding their molecular targets and mechanisms of action. The current review presents a critical analysis of inhibitors of HIF-1 and HIF-2 and hypoxia-selective compounds that have been sourced from marine organisms and that might act as new chemotherapeutic candidates or serve as templates for the development of structurally similar derivatives with improved anticancer efficacy.

Temporal phosphoproteomic analysis of VEGF-A signaling in HUVECs: an insight into early signaling events associated with angiogenesis

Vascular endothelial growth factor-A (VEGF-A) is one of the primary factors promoting angiogenesis in endothelial cells. Although defects in VEGF-A signaling are linked to diverse pathophysiological conditions, the early phosphorylation-dependent signaling events pertinent to VEGF-A signaling remain poorly defined. Hence, a temporal quantitative phosphoproteomic analysis was performed in human umbilical vein endothelial cells (HUVECs) treated with VEGF-A-165 for 1, 5 and 10 min. This led to the identification and quantification of 1971 unique phosphopeptides corresponding to 961 phosphoproteins and 2771 phosphorylation sites in total. Specifically, 69, 153, and 133 phosphopeptides corresponding to 62, 125, and 110 phosphoproteins respectively, were temporally phosphorylated at 1, 5, and 10 min upon addition of VEGF-A. These phosphopeptides included 14 kinases, among others. This study also captured the phosphosignaling events directed through RAC, FAK, PI3K-AKT-MTOR, ERK, and P38 MAPK modules with reference to our previously assembled VEGF-A/VEGFR2 signaling pathway map in HUVECs. Apart from a significant enrichment of biological processes such as cytoskeleton organization and actin filament binding, our results also suggest a role of AAK1-AP2M1 in the regulation of VEGFR endocytosis. Taken together, the temporal quantitative phosphoproteomics analysis of VEGF signaling in HUVECs revealed early signaling events and we believe that this analysis will serve as a starting point for the analysis of differential signaling across VEGF members toward the full elucidation of their role in the angiogenesis processes. Workflow for the identification of early phosphorylation events induced by VEGF-A-165 in HUVEC cells.

Geminal Diheteroatomic Motifs: Some Applications of Acetals, Ketals, and Their Sulfur and Nitrogen Homologues in Medicinal Chemistry and Drug Design

Acetals and ketals and their nitrogen and sulfur homologues are often considered to be unconventional and potentially problematic scaffolding elements or pharmacophores for the design of orally bioavailable drugs. This opinion is largely a function of the perception that such motifs might be chemically unstable under the acidic conditions of the stomach and upper gastrointestinal tract. However, even simple acetals and ketals, including acyclic molecules, can be sufficiently robust under acidic conditions to be fashioned into orally bioavailable drugs, and these structural elements are embedded in many effective therapeutic agents. The chemical stability of molecules incorporating geminal diheteroatomic motifs can be modulated by physicochemical design principles that include the judicious deployment of proximal electron-withdrawing substituents and conformational restriction. In this Perspective, we exemplify geminal diheteroatomic motifs that have been utilized in the discovery of orally bioavailable drugs or drug candidates against the backdrop of understanding their potential for chemical lability.

Metal Nanoparticles Immobilized on Molecularly Modified Surfaces: Versatile Catalytic Systems for Controlled Hydrogenation and Hydrogenolysis

The synthesis and use of supported metal nanoparticle catalysts have a long-standing tradition in catalysis, typically associated with the field of heterogeneous catalysis. More recently, the development and understanding of catalytic systems composed of metal nanoparticles (NPs) that are synthesized from organometallic precursors on molecularly modified surfaces (MMSs) have opened a conceptually new approach to the design of multifunctional catalysts (NPs@MMS). These complex yet fascinating materials bridge molecular ("homogeneous") and material ("heterogeneous") approaches to catalysis and provide access to catalytic systems with tailor-made reactivity through judicious combinations of supports, molecular modifiers, and nanoparticle precursors. A particularly promising field of application is the controlled activation and transfer of dihydrogen, enabling highly selective hydrogenation and hydrogenolysis reactions as relevant for the conversion of biogenic feedstocks and platform chemicals as well as for novel synthetic pathways to fine chemicals and even pharmaceuticals. Consequently, the topic offers an emerging field for interdisciplinary research activities involving organometallic chemists, material scientists, synthetic organic chemists, and catalysis experts.This Account will provide a brief overview of the historical background and cover examples from the most recent developments in the field. A coherent account on the methodological and experimental basis will be given from the long-standing experience in our laboratories. MMSs are widely accessible via chemisorption and physisorption methods for the generation of stable molecular environments on solid surfaces, whereby a special emphasis is given here to ionic liquid-type molecules as modifiers (supported ionic liquid phases, SILPs) and silica as support material. Metal nanoparticles are synthesized following an organometallic approach, allowing the controlled formation of small and uniformly dispersed monometallic or multimetallic NPs in defined composition. A combination of techniques from molecular and material characterization provides a detailed insight into the structure of the resulting materials across various scales (electron microscopy, solid-state NMR, XPS, XAS, etc.).The molecular functionalities grafted on the silica surface have a pronounced influence on the formation, stabilization, and reactivity of the NPs. The complementary and synergistic fine-tuning of the metal and its molecular environment in NPs@MMSs allow in particular the control of the activation of hydrogen and its transfer to substrates. Monometallic (Ru, Rh, Pd) monofunctional NPs@MMSs possess excellent activities for the hydrogenation of alkenes, alkynes, and arenes for which a nonpolarized (homolytic) activation of H2 is predominant. The incorporation of 3d metals in noble metal NPs to give bimetallic (FeRu, CoRh, etc.) monofunctional NPs@MMSs favors a more polarized H2 activation and thus its transfer to the C═O bond, while at the same time preventing the arrangement of noble metal atoms necessary for ring hydrogenation. The incorporation of reactive functionalities, such as, for example, a -SO3H moiety on NPs@MMSs, results in bifunctional catalysts enabling the heterolytic cleavage corresponding to a formal H-/H+ transfer. Consequently, such catalysts possess excellent deoxygenation activity with strong synergistic effects arising from an intimate contact between the nanoparticles and the molecular functionality.While many more efforts are still required to explore, control, and understand the chemistry of NPs@MMS catalysts fully, the currently available examples already highlight the large potential of this approach for the rational design of multifunctional catalytic systems.

Discovery of Novel Small-Molecule Antiangiogenesis Agents to Treat Diabetic Retinopathy

Diabetic retinopathy is the leading cause of blindness which is associated with excessive angiogenesis. Using the structure of wondonin marine natural products, we previously created a scaffold to develop a novel type of antiangiogenesis agent that possesses minimized cytotoxicity. To overcome its poor pharmaceutical properties, we further modified the structure. A new scaffold was derived in which the stereogenic carbon was changed to nitrogen and the 1,2,3-triazole ring was replaced by an alkyl chain. By comparing the bioactivity versus cytotoxicity, compound 31 was selected, which has improved aqueous solubility and an enhanced selectivity index. Mechanistically, 31 suppressed angiopoietin-2 (ANGPT2) expression induced by high glucose in retinal cells and exhibited in vivo antiangiogenic activity in choroidal neovascularization and oxygen-induced retinopathy mouse models. These results suggest the potential of 31 as a lead to develop antiangiogenic small-molecule drugs to treat diabetic retinopathy and as a chemical tool to elucidate new mechanisms of angiogenesis.

Current advances in the synthetic strategies of 2-arylbenzothiazole

Benzothiazole is a privileged scaffold in the field of synthetic and medicinal chemistry. Its derivatives and metal complexes possess a gamut of pharmacological properties and high degree of structural diversity that has proven it vital for the investigation for novel therapeutics. The 2nd position of benzothiazole is the most active site that makes 2-arylbenzothiazole as felicitous scaffolds in pharmaceutical chemistry. The extensive significance of benzo-fused heterocyclic moieties formation has led to broad and valuable different approaches for their synthesis. This review deals with the synthetic approaches developed so far for the synthesis of 2-arylbenzothiazoles. Moreover, this article abridges the publications devoted to the synthesis of this moiety over the last 6 years. This study gives a current precis of research on the fabrication of 2-arylbenzothiazoles through different synthetic pathways and shall be helpful for researchers and scientists who are working in this field to make more potent biologically active benzothiazole-based drugs.

Selective hydrodeoxygenation of hydroxyacetophenones to ethyl-substituted phenol derivatives using a FeRu@SILP catalyst

The selective hydrodeoxygenation of hydroxyacetophenone derivatives is achieved opening a versatile pathway for the production of valuable substituted ethylphenols from readily available substrates. Bimetallic iron ruthenium nanoparticles immobilized on an imidazolium-based supported ionic liquid phase (Fe25Ru75@SILP) show high activity and stability for a broad range of substrates without acidic co-catalysts.

Cytotoxic Scalarane Sesterterpenes from the Sponge Hyrtios erectus

Twelve new sesterterpenes along with eight known sesterterpenes were isolated from the marine sponge Hyrtios erectus collected off the coast of Chuuk Island, the Federated State of Micronesia. Based upon a combination of spectroscopic and computational analyses, these compounds were determined to be eight glycine-bearing scalaranes (1–8), a 3-keto scalarane (9), two oxidized-furan-bearing scalaranes (10 and 11), and a salmahyrtisane (12). Several of these compounds exhibited weak antiproliferation against diverse cancer cell lines as well as moderate anti-angiogenesis activities. The antiproliferative activity of new compound 4 was found to be associated with G0/G1 arrest in the cell cycle.

Cp*Co(III)-Catalyzed γ-Selective C-H Allylation/Hydroamination Cascade for the Synthesis of Dihydroisoquinolines

A Cp*Co(III)-catalyzed γ-selective C-H allylation/hydroamination cascade toward the synthesis of 3,4-dihydroisoquinolines (DHIQs) has been successfully developed, starting from NH ketimines and allyl carbonates. Notably, highly efficient and γ-selective C-H allylations were accomplished using γ-substituted allyl reagents, thus overcoming the issues of poor α/γ selectivity and low reactivity of previous transition metal-catalyzed C-H allylations. The stereochemistry of allyl carbonates was a crucial factor, and synthesis of the DHIQs was achieved using (Z)-allyl carbonates.

Phenalenones from a Marine-Derived Fungus Penicillium Sp

Six new phenalenone derivatives (1–6), along with five known compounds (7–11) of the herqueinone class, were isolated from a marine-derived fungus Penicillium sp. The absolute configurations of these compounds were assigned based on chemical modifications and their specific rotations. 4-Hydroxysclerodin (6) and an acetone adduct of a triketone (7) exhibited moderate anti-angiogenetic and anti-inflammatory activities, respectively, while ent-peniciherqueinone (1) and isoherqueinone (9) exhibited moderate abilities to induce adipogenesis without cytotoxicity.

Bromopyrrole Alkaloids from the Sponge Agelas kosrae

Two new sceptrin derivatives (1,2) and eight structurally-related known bromopyrrole-bearing alkaloids were isolated from the tropical sponge Agelas kosrae. By a combination of spectroscopic methods, the new compounds, designated dioxysceptrin (1) and ageleste C (2), were determined to be structural analogs of each other that differ at the imidazole moiety. Dioxysceptrin was also found to exist as a mixture of α-amido epimers. The sceptrin alkaloids exhibited weak cytotoxicity against cancer cells. Compounds 1 and 2 also moderately exhibited anti-angiogenic and isocitrate lyase-inhibitory activities, respectively.