Iridium(III) complexes decorated with silicane-modified rhodamine: near-infrared light-initiated photosensitizers for efficient deep-tissue penetration photodynamic therapy.

Meeting the demand for efficient photosensitizers in photodynamic therapy (PDT), a series of iridium(III) complexes decorated with silicane-modified rhodamine (Si-rhodamine) was meticulously designed and synthesized. These complexes demonstrate exceptional PDT potential owing to their strong absorption in the near-infrared (NIR) spectrum, particularly responsive to 808 nm laser stimulation. This feature is pivotal, enabling deep-penetration laser excitation and overcoming depth-related challenges in clinical PDT applications. The molecular structures of these complexes allow for reliable tuning of singlet oxygen generation with NIR excitation, through modification of the cyclometalating ligand. Notably, one of the complexes (4) exhibits a remarkable ROS quantum yield of 0.69. In vivo results underscore the efficacy of 4, showcasing significant tumor regression at depths of up to 8.4 mm. This study introduces a promising paradigm for designing photosensitizers capable of harnessing NIR light effectively for deep PDT applications.

Base-Exchange Enabling the Visualization of SARM1 Activities in Sciatic Nerve-Injured Mice.

Enzymes are important in homeostasis in living organisms. Since abnormal enzyme activities are highly associated with many human diseases, detection of in vivo activities of a specific enzyme is important to study the pathology of the related diseases. In this work, we have designed and synthesized a series of new small-molecule-activatable fluorescent probes for the imaging of Sterile Alpha and TIR Motif-containing 1 (SARM1) activities based on its transglycosidase activities (base-exchange reactions of NAD+). Probe 1a was found to undergo base-exchange reactions with NAD+ in the presence of activated SARM1 but not CD38 nor NADase and formed a highly emissive product AD-1a [about a 100-fold fluorescence enhancement in 20 min with a 150 nm (5665 cm-1) Stokes shift and a 100 nm (3812 cm-1) red shift]. This probe exhibited a higher reactivity and sensitivity than those commonly used for SARM1 imaging. The utilities of 1a have also been demonstrated in live-cell imaging and detection of in vivo activities of SARM1 in a sciatic nerve injury mouse model.

Enantio- and Regioselective Construction of 1,4-Diamines via Cascade Hydroamination of Methylene Cyclopropanes.

Despite the widespread existence of chiral 1,4-diamines in bioactive molecules and their applications in asymmetric catalysis, the catalytic and asymmetric synthesis of such structures from readily accessible substrates remains a long-standing challenge. Here, we report a Cu-catalyzed asymmetric cascade hydroamination protocol to construct a wide range of chiral 1,4-diamine derivatives in high yields with excellent enatioselectivities (up to 95 % yield and up to >99 % ee). The use of two hydroxylamine esters containing different functionalized amino groups allowed us to increase the complexity of the final 1,4-diamine structures. The desired products could be easily transformed into chiral 1,4-diamines and chiral NH2 -Terfenadine. Mechanistic study demonstrates that this reaction proceeds through hydroamination ring-opening and cascade hydroamination sequence.

Room Temperature Aerobic Peroxidation of Organic Substrates Catalyzed by Cobalt(III) Alkylperoxo Complexes.

Room temperature aerobic oxidation of hydrocarbons is highly desirable and remains a great challenge. Here we report a series of highly electrophilic cobalt(III) alkylperoxo complexes, CoIII(qpy)OOR supported by a planar tetradentate quaterpyridine ligand that can directly abstract H atoms from hydrocarbons (R'H) at ambient conditions (CoIII(qpy)OOR + R'H → CoII(qpy) + R'• + ROOH). The resulting alkyl radical (R'•) reacts rapidly with O2 to form alkylperoxy radical (R'OO•), which is efficiently scavenged by CoII(qpy) to give CoIII(qpy)OOR' (CoII(qpy) + R'OO• → CoIII(qpy)OOR'). This unique reactivity enables CoIII(qpy)OOR to function as efficient catalysts for aerobic peroxidation of hydrocarbons (R'H + O2 → R'OOH) under 1 atm air and at room temperature.

Permeant fluorescent probes visualize the activation of SARM1 and uncover an anti-neurodegenerative drug candidate.

SARM1 regulates axonal degeneration through its NAD-metabolizing activity and is a drug target for neurodegenerative disorders. We designed and synthesized fluorescent conjugates of styryl derivative with pyridine to serve as substrates of SARM1, which exhibited large red shifts after conversion. With the conjugates, SARM1 activation was visualized in live cells following elevation of endogenous NMN or treatment with a cell-permeant NMN-analog. In neurons, imaging documented mouse SARM1 activation preceded vincristine-induced axonal degeneration by hours. Library screening identified a derivative of nisoldipine (NSDP) as a covalent inhibitor of SARM1 that reacted with the cysteines, especially Cys311 in its ARM domain and blocked its NMN-activation, protecting axons from degeneration. The Cryo-EM structure showed that SARM1 was locked into an inactive conformation by the inhibitor, uncovering a potential neuroprotective mechanism of dihydropyridines.

Peroxide- and transition metal-free electrochemical synthesis of α,ß-epoxy ketones.

A novel electrochemical method for the synthesis of α,ß-epoxy ketones is reported. With KI as the redox mediator, methyl ketones reacted with aldehydes under peroxide- and transition metal-free electrolytic conditions and afforded α,ß-epoxy ketones in one pot (36 examples, 52-90% yield). This safe and environmental-friendly method has a broad substrate scope and can readily provide a variety of α,ß-epoxy ketones in gram-scales for evaluation of their anti-cancer activities.

Synthesis and Evaluation of Novel Anticancer Compounds Derived from the Natural Product Brevilin A.

Cancer is the second leading cause of death globally, responsible for an estimated 9.6 million deaths in 2018, and this burden continues to increase. Therefore, there is a clear and urgent need for novel drugs with increased efficacy for the treatment of different cancers. Previous research has demonstrated that brevilin A (BA) exerts anticancer activity in various cancers, including human multiple myeloma, breast cancer, lung cancer, and colon carcinoma, suggesting the anticancer potential present in the chemical scaffold of BA. Here, we designed and synthesized a small library of 12 novel BA derivatives and evaluated the biological anticancer effects of the compounds in various cancer cell lines. The results of this structure-activity relationship study demonstrated that BA derivatives BA-9 and BA-10 possessed significantly improved anticancer activity toward lung, colon, and breast cancer cell lines. BA-9 and BA-10 could more effectively reduce cancer cell viability and induce DNA damage, cell-cycle arrest, and apoptosis when compared with BA. Our findings represent a significant step forward in the development of novel anticancer entities.

Fluorescence Analysis: Shedding Light on Biological Systems.

Shining examples: ChemPlusChem is pleased to present its Special Collection on Fluorescent Biomolecules and their Building Blocks, organized in collaboration with Guest Editors Ka-Leung Wong, Chi-Sing Lee, and Ga-Lai Law. This collection features a top range of contributions related to the development and use of new fluorescent reporters, including lanthanide- and transition-metal-based probes, fluorescent nucleoside analogues, and fluorescent nanocelluloses.

Brevilin A Induces Cell Cycle Arrest and Apoptosis in Nasopharyngeal Carcinoma.

Nasopharyngeal carcinoma (NPC) is one of the most common malignant cancers in Southeast Asia and Southern China. Centipeda minima extract (CME) had previously demonstrated anti-cancer effects in human NPC. Brevilin A, a sesquiterpene lactone isolated from C. minima, has been reported to exhibit biological activities. In this study, we investigated its anti-NPC effect and further explored its molecular mechanisms. The effects of brevilin A were tested in the NPC cell lines CNE-1, CNE-2, SUNE-1, HONE1, and C666-1. Effects of brevilin A on cell viability were determined by MTT assay, and cell cycle and apoptosis were detected by flow cytometry. The molecular mechanism of cell cycle regulation and apoptosis were investigated via Western blot. Results showed that brevilin A inhibited NPC cell viability in a concentration- and time-dependent manner. Brevilin A induced cell cycle arrest at G2/M and induced apoptosis. Western blot results demonstrated that brevilin A could down-regulate cyclin D3, cdc2, p-PI3K, p-AKT, p-mTOR, and p-STAT3, while up-regulating cleaved PARP, cleaved caspase 9, and Bax. Regulation of cyclin B1, cdk6, and Bcl-2 expression by brevilin A showed dynamic changes according to dose and time. In the tumor xenograft model, brevilin A could reduce tumor growth, at a similar magnitude to cisplatin. However, notably, whereas cisplatin treatment led to significant weight loss in treated mice, treatment with brevilin A did not, indicating its relative lack of toxicity. Taken together, brevilin A regulated cell cycle, activated the caspase signaling pathway, and inhibited PI3K/AKT/mTOR and STAT3 signaling pathways in vitro, and exhibited similar efficacy to the common chemotherapeutic cisplatin in vivo, without its associated toxicity. These findings provide a framework for the preclinical development of brevilin A as a chemotherapeutic for NPC.

Synthesis of the Tricyclic Picrotoxane Motif by an Oxidative Cascade Cyclization.

An oxidative cascade cyclization of ß-keto esters has been developed for the construction of the tricyclic picrotoxane motif in a single step, and DFT calculations suggested a possible cationic cyclization mechanism. This cascade cyclization can be operated on a 20 g scale to obtain a 77% total yield of the tricyclic products, which in turn can be converted to versatile intermediates for further elaboration to picrotoxanes and their structurally related compounds.

Dihydrochalcone-derived polyphenols from tea crab apple (Malus hupehensis) and their inhibitory effects on α-glucosidase in vitro.

Three dihydrochalcone-derived polyphenols, huperolides A-C (1-3), along with thirteen known compounds (4-16) were isolated from the leaves of Malus hupehensis, the well-known tea crab apple in China. Their chemical structures were elucidated by extensive spectroscopic analysis including NMR (HSQC, HMBC, 1H-1H COSY and ROESY), HRMS and CD spectra. Huperolide A is a polyphenol with a new type of carbon skeleton, while huperolides B and C are a couple of atropisomers, which were isolated from natural sources for the first time. The antihyperglycemic effects of the isolated compounds were evaluated based on assaying their inhibitory activities against α-glucosidase. As a result, phlorizin (4), 3-hydroxyphloridzin (5), 3-O-coumaroylquinic acid (12) and ß-hydroxypropiovanillone (15) showed significant concentration-dependent inhibitory effects on α-glucosidase. Therefore, those compounds might be responsible for the antihyperglycemic effect of this herb, and are the most promising compounds to lead discovery of drugs against diabetes.

Arnicolide D, from the herb Centipeda minima, Is a Therapeutic Candidate against Nasopharyngeal Carcinoma.

Nasopharyngeal carcinoma (NPC) is a high morbidity and mortality cancer with an obvious racial and geographic bias, particularly endemic to Southeast China. Our previous studies demonstrated that Centipeda minima extract (CME) exhibited anti-cancer effects in human NPC cell lines. Arnicolide C and arnicolide D are sesquiterpene lactones isolated from Centipeda minima. In this study, for the first time, we investigated their anti-NPC effects and further explored the related molecular mechanisms. The effects of both arnicolide C and arnicolide D were tested in NPC cells CNE-1, CNE-2, SUNE-1, HONE1, and C666-1. The results showed that the two compounds inhibited NPC cell viability in a concentration- and time-dependent manner. As the inhibitory effect of arnicolide D was the more pronounced of the two, our following studies focused on this compound. Arnicolide D could induce cell cycle arrest at G2/M, and induce cell apoptosis. The molecular mechanism of cell cycle regulation and apoptosis induction was investigated, and the results showed that arnicolide D could downregulate cyclin D3, cdc2, p-PI3K, p-AKT, p-mTOR, and p-STAT3, and upregulate cleaved PARP, cleaved caspase 9, and Bax. Regulation of cyclin B1, cdk6, and Bcl-2 expression by arnicolide D showed dynamic changes according to dose and time. Taken together, arnicolide D modulated the cell cycle, activated the caspase signaling pathway, and inhibited the PI3K/AKT/mTOR and STAT3 signaling pathways. These findings provide a solid base of evidence for arnicolide D as a lead compound for further development, and act as proof for the viability of drug development from traditional Chinese medicines.

Total Synthesis-Enabled Systematic Structure-Activity Relationship Study for Development of a Bioactive Alkyne-Tagged Derivative of Neolaxiflorin L.

Neolaxiflorin L (NL) is a low-abundant Isodon 7,20-epoxy- ent-kuarenoid and was found to be a promising anticancer drug candidate in our previous study. In order to study its structure-activity relationship (SAR), a diversity-oriented synthetic route toward two libraries of (±)-NL analogs, including analogs containing different functionalities in the same 7,20-epoxy- ent-kuarene skeleton and analogs with skeletal changes, has been developed. The results of this total synthesis-enabled SAR successfully led to a bioactive alkyne-tagged NL derivative, which could be a useful probe for proteomics studies.

In(OTf)3-Catalyzed Cascade Cyclization for Construction of Oxatricyclic Compounds.

A highly diastereoselective cascade cyclization reaction has been developed for establishing a series of oxatricyclic compounds using Chan's diene and simple keto alkynal substrates with only 1 mol % of In(OTf)3 as the catalyst in 82-92% yields. The potential utility of this synthetic strategy has been demonstrated in model studies for the construction the core structures of 1α,8α:4α,5α-diepoxy-4,5-dihydroosmitopsin and cortistatin A.

Formal Synthesis of (+)-Phomactin A.

A concise formal synthesis of (+)-phomactin A has been achieved. The key features of this synthetic strategy involve a one-pot Prins/Conia-ene cyclization protocol for the construction of the highly functionalized 1-oxadeclin core (AB ring) and a late-stage direct γ-hydroxylation of enone for the installation of the C ring.

Scalable synthesis enabling multilevel bio-evaluations of natural products for discovery of lead compounds.

Challenges in the development of anti-cancer chemotherapeutics continue to exist, particularly with respect to adverse effects and development of resistance, underlining the need for novel drugs with good safety profiles. Natural products have proven to be a fertile ground for exploitation, and development of anti-cancer drugs from structurally complex natural products holds promise. Unfortunately, this approach is often hindered by low isolation yields and limited information from preliminary cell-based assays. Here we report a concise and scalable synthesis of a series of low-abundance Isodon diterpenoids (a large class of natural products with over 1000 members isolated from the herbs of genus Isodon, which are well-known folk medicines for the treatment of inflammation and cancer), including eriocalyxin B, neolaxiflorin L and xerophilusin I. These scalable syntheses enable multilevel bio-evaluation of the natural products, in which we identify neolaxiflorin L as a promising anti-cancer drug candidate.

Tunable Cyclization Strategy for the Synthesis of Zizaene-, allo-Cedrane-, seco-Kaurane-, and seco-Atesane-Type Skeletons.

A versatile Lewis acid-mediated cyclization strategy has been developed for selectively establishing zizaene-, allo-cedrane-, seco-kaurane-, and seco-atesane-type skeletons. The zizaene- and seco-atesane-type skeletons can be obtained in a cascade manner, which involves Diels-Alder reaction of cyclic enones with bis-silyloxy dienes and carbocyclization of yne-enolates through Lewis acid dependent 5- or 6-exo-dig modes. This cyclization strategy was also employed for the core synthesis of tashironin.

Diastereoselective Total Synthesis of (±)-Basiliolide B and (±)-epi-8-Basiliolide B.

The C8 and C9 stereogenic centers of the basiliolide/transtaganolide family have been established stereoselectively using a cyclopropane ring-opening strategy, which has been studied by DFT calculations of a variety of lithium-chelating models. The highly functionalized intermediates obtained in this strategy were successfully employed for the diastereoselective total synthesis of (±)-basiliolide B and (±)-epi-8-basiliolide B. The decalin core with a lactone bridge was constructed via a 2-pyrone Diels-Alder (DA) cycloaddition, and the unprecedented seven-membered acyl ketene acetal was established by a biomimetic intramolecular O-acylation cyclization.

Study of the Aggregation of DNA-Capped Gold Nanoparticles: A Smart and Flexible Aptasensor for Spermine Sensing.

A smart gold nanoparticle based aptasensor is developed for the sensing of this biomarker in a convenient and fast manner. A comprehensive study was performed to elucidate the driving force of DNA adsorption, different factors' effects, such as gold nanoparticle size, DNA length, concentration, and working pH towards spermine sensing by using UV/Vis absorption spectroscopy and isothermal titration calorimetry. It was found that the developed aptasensor could detect spermine by two different sensing mechanisms simply by adjusting the DNA concentration without complicated procedures. Good performance in complicated matrices was proven by the satisfactory results obtained in the spike analysis of both artificial urine and clinical urine samples. Such a flexible and smart approach described here would provide a useful tool for the fast sensing of spermine and prostate cancer screening.

A smart "off-on" gate for the in situ detection of hydrogen sulphide with Cu(ii)-assisted europium emission.

A water-soluble and emissive Eu-complex (EuL1) bearing a DO3A(Eu3+)-pyridine-aza-crown motif has been prepared and its Cu2+ complex has been demonstrated to be a smart luminescence "off-on" gate for H2S detection in water with a nano-molar detection limit (60 nM). EuL1 binds to Cu2+ ions selectively (KB = 1.2 × 105 M-1) inducing 17-fold luminescence quenching and forming a 1 : 1 stoichiometric complex (EuL1-Cu2+), which responds to H2S selectively with restoration of the original Eu emission of EuL1 followed by a further 40-fold luminescence enhancement, forming a 1 : 1 stoichiometric complex (EuL1-Na2S, KB = 1.5 × 104 M-1). Without Cu2+ ions, EuL1 showed non-specific binding towards H2S with only a 5-fold luminescence enhancement.