Lynamicin D an antimicrobial natural product affects splicing by inducing the expression of SR protein kinase 1

A biomimetic approach to lycogarubin C, lynamicin D and related analogues

An efficient and biomimetic synthetic approach to 3,4-diindolylpyrrole-2,5-dicarboxylate derivatives, including lycogarubin C, lynamicin D and related analogues, was discovered. The crucial transformation included the one-pot formation of two C-N bonds and one C-C bond to construct characteristic pyrrole rings.

Naturally Occurring Organohalogen Compounds-A Comprehensive Review

The present volume is the third in a trilogy that documents naturally occurring organohalogen compounds, bringing the total number-from fewer than 25 in 1968-to approximately 8000 compounds to date. Nearly all of these natural products contain chlorine or bromine, with a few containing iodine and, fewer still, fluorine. Produced by ubiquitous marine (algae, sponges, corals, bryozoa, nudibranchs, fungi, bacteria) and terrestrial organisms (plants, fungi, bacteria, insects, higher animals) and universal abiotic processes (volcanos, forest fires, geothermal events), organohalogens pervade the global ecosystem. Newly identified extraterrestrial sources are also documented. In addition to chemical structures, biological activity, biohalogenation, biodegradation, natural function, and future outlook are presented.

Biomimetic Total Synthesis of the Spiroindimicin Family of Natural Products

A unified strategy for the biomimetic total synthesis of the spiroindimicin family of natural products was reported. Key transformations include a one-pot two-enzyme-catalyzed oxidative dimerization of L-tryptophan/5-chloro-L-tryptophan to afford the bis-indole precursors chromopyrrolic acid/5',5''-dichloro-chromopyrrolic acid, and regioselective C3'-C2'' and C3'-C4'' bond formation converting a common bis-indole skeleton to two skeletally different natural products, including (±)-spiroindimicins D and G with a [5,5] spiro-ring skeleton, and (±)-spiroindimicins A and H with a [5,6] spiro-ring skeleton, respectively.

Marine Pyrrole Alkaloids

Nitrogen heterocycles are essential parts of the chemical machinery of life and often reveal intriguing structures. They are not only widespread in terrestrial habitats but can also frequently be found as natural products in the marine environment. This review highlights the important class of marine pyrrole alkaloids, well-known for their diverse biological activities. A broad overview of the marine pyrrole alkaloids with a focus on their isolation, biological activities, chemical synthesis, and derivatization covering the decade from 2010 to 2020 is provided. With relevant structural subclasses categorized, this review shall provide a clear and timely synopsis of this area.

Total synthesis of (+)-spiroindimicin A and congeners unveils their antiparasitic activity

The spiroindimicins are a unique class of chlorinated indole alkaloids characterized by three heteroaromatic rings structured around a congested spirocyclic stereocenter. Here, we report the first total synthesis of (+)-spiroindimicin A, which bears a challenging C-3′/C-5′′-linked spiroindolenine. We detail our initial efforts to effect a biomimetic oxidative spirocyclization from its proposed natural precursor, lynamicin D, and describe how these studies shaped our final abiotic 9-step solution to this complex alkaloid built around a key Pd-catalyzed asymmetric spirocyclization. Scalable access to spiroindimicins A, H, and their congeners has enabled discovery of their activity against several parasites relevant to human health, providing potential starting points for new therapeutics for the neglected tropical diseases leishmaniasis and African sleeping sickness.

Spiroindimicins A and H have been synthesized for the first time via a key palladium-catalyzed spirocyclization. Access to these alkaloids and several congeners has allowed the discovery of their antiparasitic properties.

Cross-coupling reactions towards the synthesis of natural products

Cross-coupling reactions are powerful synthetic tools for the formation of remarkable building blocks of many naturally occurring molecules, polymers and biologically active compounds. These reactions have brought potent transformations in chemical and pharmaceutical disciplines. In this review, we have focused on the use of cross-coupling reactions such as Suzuki, Negishi, Heck, Sonogashira and Stille in the total synthesis of some natural products of recent years (2016-2020). A short introduction of mentioned cross-coupling reactions along with highlighted aspects of natural products has been stated in separate sections. Additionally, few examples of natural products via incorporation of more than one type of cross-coupling reaction have also been added to demonstrate the importance of these reactions in organic synthesis.

Synthesis and evaluation of 6-[18F]fluoro-3-(pyridin-3-yl)-1H-indole as potential PET tracer for targeting tryptophane 2, 3-dioxygenase (TDO)

INTRODUCTION

The increase in expression of tryptophan 2, 3-dioxygenases (TDO) and indoleamine 2,3-dioxygenase (IDO) have been reported as potential tumor biomarkers. TDO and IDO are enzymes that catalyze the first and rate-limiting step of the kynurenine pathway. Positron emitting tomography (PET) tracers investigating the kynurenine pathway may allow for the detection of different disease pathologies in vivo including cancer. However, current PET tracers being developed for TDO and IDO have suffered from either multi-step low yielding syntheses or de-fluorination of the tracer in vivo.

RESULTS

TDO inhibitors based on 6-fluoroindole with C3 substituents are a class of small molecules that have been shown to bind to TDO effectively, restore tryptophan concentration and decrease the production of immunosuppressive metabolites. The compound 6-fluoro-3-(pyridine-3-yl)-1H-indole has been reported to have high in vitro affinity for TDO. Herein we report the fully automated radiosynthesis of 6-[¹⁸F]fluoro-3-(pyridine-3-yl)-1H-indole [¹⁸F]4 using a copper-mediated nucleophilic ¹⁸F-fluorination resulting in a non-corrected yield of 5 to 6% of the tracer with a radiochemical purity of >99% after 4 h. Small animal dynamic PET/CT imaging of [¹⁸F]4 intravenously injected into normal C57BL/6 mice revealed rapid accumulation in heart and brain, reaching maximum occupancy in heart (10.9% ID/g) and brain (8.1% ID/g) at 1.75 min and 2.25 min, respectively. Furthermore, these in vivo studies revealed no de-fluorination of the tracer, as evidence by the absence of [¹⁸F]fluoride accumulation in bone.

CONCLUSION

In vitro studies demonstrate that 4 has good affinity for hTDO and the radiolabeled analogue [¹⁸F]4 can be synthesized with suitable radiochemical yields. [¹⁸F]4 demonstrates good uptake in the brain and the radiolabeled compound shows no de-fluorination in vivo in C57BL/6 mice.

Therapeutic approaches to treat human spliceosomal diseases

Mutated RNA splicing machinery drives many human diseases and is a promising therapeutic target for engineering and small molecule therapy. In the case of mutations in individual genes that cause them to be incorrectly spliced, engineered splicing factors can be introduced to correct splicing of these aberrant transcripts and reduce the effects of the disease phenotype. Mutations that occur in certain splicing factor genes themselves have been implicated in many cancers, particularly myelodysplastic syndromes. Small molecules that target splicing factors have been developed as therapies to preferentially induce apoptosis in these cancer cells. Specifically, drugs targeting the splicing factor SF3B1 have led to recent clinical trials. Here, we review the role of alternative splicing in disease, approaches to rescue incorrect splicing using engineered splicing factors, and small molecule splicing inhibitors developed to treat hematological cancers.

One-Pot Approach for the Synthesis of Bis-indole-1,4-disubstituted-1,2,3-triazoles

A new strategy for the synthesis of bis-indoletriazoles was developed using a sequential one-pot four-step procedure via I₂ and H₂SO₄-SiO₂ catalyzed Friedel-Crafts reactions of indole with aldehyde followed by N-alkylation with propargyl bromide, azidation, and copper(I)-catalyzed azide alkyne cycloaddition (CuAAC). The reaction proceeded smoothly at room temperature in a short time, and a series of bis-indoletriazoles were obtained in good to excellent yields proving the generality of this one-pot methodology.

miR-126 Functions as a Tumor Suppressor by Targeting SRPK1 in Human Gastric Cancer

The expression of miR-126 and serine–arginine protein kinase 1 (SRPK1) are linked to tumor development; nevertheless, its role in the tumor growth and invasion of gastric cancer (GC) and the underlying mechanism have not been clarified. Here the expression and role of miR-126 and SRPK1 were investigated in GC tissues and cells by in vitro assay, and then targets of miR-126 were identified by dual-luciferase reporter assay. In this study, miR-126 expression was downregulated and associated with lymph node metastasis and poor prognosis as well as SRPK1 expression. In vitro assay revealed that miR-126 obviously inhibited the proliferative and invasive capabilities of GC cells. The dual-luciferase reporter assay showed that miR-126 targets the 3′-UTR of SRPK1 and downregulates its expression. SRPK1 overexpression promoted cell migration and invasion. In conclusion, the reduced expression of miR-126 is suggestive of the risk of GC recurrence and metastasis, and miR-126 functions as a tumor suppressor by targeting SRPK1 expression in the development of GC.

The emerging role of alternative splicing in senescence and aging

Deregulation of precursor mRNA splicing is associated with many illnesses and has been linked to age-related chronic diseases. Here we review recent progress documenting how defects in the machinery that performs intron removal and controls splice site selection contribute to cellular senescence and organismal aging. We discuss the functional association linking p53, IGF-1, SIRT1, and ING-1 splice variants with senescence and aging, and review a selection of splicing defects occurring in accelerated aging (progeria), vascular aging, and Alzheimer's disease. Overall, it is becoming increasingly clear that changes in the activity of splicing factors and in the production of key splice variants can impact cellular senescence and the aging phenotype.

The crucial role of SRPK1 in IGF-1-induced EMT of human gastric cancer

In recent years, the insulin-like growth factor (IGF-1) and serine-arginine protein kinase 1 (SRPK1) have been reported to be implicated in the pithelial-mesenchymal transition (EMT) in many kinds of malignancies. However, the potential roles of IGF-1-SRPK1 signaling in the EMT of gastric cancer (GC) have not been investigated. In the present study, the in-vitro assays were used to investigate the molecular role of SRPK1 in cell cycle, motility and invasiveness. We demonstrated that the expressions of SRPK1 or insulin-like growth factor receptor 1 (IGF1R) were significantly increased in GC tissues and cells than those in normal tissues and GES-1 cells, and closely associated with metastasis, stage and prognosis. Western blot analysis showed that IGF-1 treatment can induce the expression of p-AKT and EMT biomarkers (N-cadherin, MMP2 and Slug) in a dose-dependent fashion in MGC803 and BGC823 cells. On the other hand, the knockdown of SRPK1 attenuated IGF-1-induced increase of EMT biomarkers and p-AKT. Besides, in-vitro analysis showed that knockdown of SRPK1 induced cell cycle arrest in G0/G1 phase, and affected cell migration and invasion. In conclusion, IGF-1-IGF1R pathway induced the expression of SRPK1 to control the progression of EMT via AKT pathway in the development of GC. Our findings lay a promising foundation for the IGF-1-IGF1R axis-targeting therapy in GC patients.