ABSTRACT SARS-CoV-2 has undergone rapid genetic evolution, leading to the emergence of new variants with distinct mutations impacting global public health. Upon infection, the virus triggers a robust inflammatory response characterized by the release of pro-inflammatory cytokines, which play a central role in lung injury. It also alters the host antioxidant response, causing oxidative stress that supports viral replication and cytokine overproduction. This study investigated key pathogenic effectors in Calu-3 and A549-ACE2/TMPRSS2 cells infected with SARS-CoV-2 variants, focusing on replication kinetics, cellular redox state, and inflammatory cytokine profile. A dramatic redox alteration in terms of glutathione (GSH) and Cysteine (Cys) was observed at 48 h p.i., along with a strong pro-inflammatory cytokine response , likely via activation of the JNK/AP-1 signaling pathway. To counteract these effects, two thiol molecules were tested: I-152, a monothiol conjugate of N-Acetyl-Cysteine (NAC) and β-mercaptoethylamine (MEA) and its dithiol derivative, I-152SdAc. Thiols restored GSH balance by enhancing the expression of Nrf2-mediated genes, such as glutamate-Cys ligase modifier subunit (GCLM), and counteracted AP-1-mediated pathway, resulting in a significant reduction of inflammation and viral replication. Antiviral and anti-inflammatory activities of thiols were confirmed in NHBE cells. These findings highlight that redox imbalance is a key pathogenetic event in SARS-CoV-2 infection. Notably, besides Nrf2 and AP-1, other redox-sensitive factors, such as the CHAC glutathione-specific gamma-glutamyl-cyclotransferase 1 (CHAC1), seem to contribute to the pathogenesis and may represent a new potential therapeutic target of redox active compounds. Therefore, the thiol-derived molecules act as broadly effective compounds by limiting virus replication and inflammation.

This study aimed to estimate the ADME properties and safety of I-152, a conjugate of N-acetyl-l-cysteine (NAC) and S-acetylcysteamine (also known as S-acetyl-β-mercaptoethylamine; SMEA), linked by an amide bond. Its potent antioxidant and pro-glutathione effects make it of interest for a range of conditions linked to oxidative stress, such as infectious diseases and inflammation. I-152 was characterized in vitro for its stability in plasma, liver microsomes, and hepatocytes; its protein binding; and its AB BA (apical-to-basolateral and basolateral-to-apical) permeability using Caco-2 cells. Derisking and preliminary safety pharmacology assays were performed through a human ether-à-go-go-related gene assay (hERG) and in vitro cellular toxicity tests. The results demonstrated that I-152 is hydrolyzed in human plasma (half-life of about 9 min), human liver microsomes, and hepatocytes, as well as in rat liver microsomes and hepatocytes. In addition, I-152 was found to be permeable across the Caco-2 monolayer, indicating good intestinal absorption. Furthermore, I-152 did not produce detectable toxic effects at concentrations up to 1 mM in vitro assays using human keratinocytes, alveolar epithelial cells, and immortalized human embryonic kidney cells (HEK293T). These findings support further preclinical evaluation as a potential redox-modulating agent and thiol-based approach for viral infections and other conditions associated with oxidative stress.

A concise and divergent asymmetric synthesis of the tetracyclic clavine alkaloids (+)-lysergol, (+) lysergine, and (+)-isolysergine has been accomplished using a novel strategy involving a chemoselective MeOH-mediated oxa-Michael addition and lactone-lactam rearrangement of appropriately functionalized spiro α-methylene-γ-butyrolactones, efficiently prepared from (R)-4-amino-Uhle's ketone and bromomethyl acrylate. The straightforward downstream modifications complement and expand upon previous asymmetric total syntheses of these natural products.

We report the development of the diastereoselective rhodium(I)‐catalyzed intramolecular conjugate addition (Hayashi‐Miyaura reaction) of robust and easily handled 4‐pinacolboronic ester D‐tryptophan derivatives tethering an activated alkene as the acceptor. This methodology provides, access to the functionalized chiral tricyclic core of the ergoline skeleton diastereoselectivity and allows further modification for the cyclization of the fused fourth ring present in several clavine alkaloids.

A selective, mild, convenient, and green protocol for the preparation of S-acyl and N-acyl glutathiones is described involving the chemical modification of glutathione (GSH) with N-acyl imidazoles at room temperature in water. The syntheses of S-acyl glutathiones were achieved in very high yields using 1 equiv. of an N-acyl imidazole in water at room temperature, without the need of a base. Double acylation of GSH with various N-acyl imidazoles in weakly basic aqueous media in the presence of N-hydroxysuccinimide (HOSu) as the activating reagent followed by selective deprotection of the S-acyl group with aqueous ammonia at room temperature gave high yields of N-acyl glutathiones. Moreover, the reaction could accommodate a diverse range of carboxylic acids such as (hetero)benzoic acids, phenylacetic acids, aliphatic acids from short-chain fatty acids (including acetic acid), long-chain polyunsaturated fatty acids, secondary or tertiary amino acids, and carboxylic acids containing clickable functional groups, fluorescent probes, or drugs.

This research investigates boronated tryptophans as potential boron delivery agents for boron neutron capture therapy (BNCT) of cancer. We synthesized both enantiomers of 5- and 6-boronotryptophans (1a and 1b) using simple and inexpensive methods. Their uptake was assessed in two human cancer cell lines, CAL27 (head and neck cancer) and U87-MG (brain cancer), and compared to l-p-boronophenylalanine (l-BPA) as a reference. To determine whether these tryptophan derivatives are substrates for large amino acid transporter 1, we performed molecular dynamics simulations to explore their transport mechanism. Our findings reveal differences in boron compound accumulation between the cancer cell lines, indicating that tryptophan derivatives could serve as effective boron carriers when the clinically used boron carrier, BPA, is ineffective.

Organocatalytic asymmetric synthesis has evolved over the years and continues to attract the interest of many researchers worldwide. Enantiopure noncanonical amino acids (ncAAs) are valuable building blocks in organic synthesis, medicinal chemistry, and chemical biology. They are employed in the elaboration of peptides and proteins with enhanced activities and/or improved properties compared to their natural counterparts, as chiral catalysts, in chiral ligand design, and as chiral building blocks for asymmetric syntheses of complex molecules, including natural products. The linkage of ncAA synthesis and enantioselective organocatalysis, the subject of this perspective, tries to imitate the natural biosynthetic process. Herein, we present contemporary and earlier developments in the field of organocatalytic activation of simple feedstock materials, providing potential ncAAs with diverse side chains, unique three-dimensional structures, and a high degree of functionality. These asymmetric organocatalytic strategies, useful for forging a wide range of C-C, C-H, and C-N bonds and/or combinations thereof, vary from classical name reactions, such as Ugi, Strecker, and Mannich reactions, to the most advanced concepts such as deracemisation, transamination, and carbene N-H insertion. Concurrently, we present some interesting mechanistic studies/models, providing information on the chirality transfer process. Finally, this perspective highlights, through the diversity of the amino acids (AAs) not selected by nature for protein incorporation, the most generic modes of activation, induction, and reactivity commonly used, such as chiral enamine, hydrogen bonding, Brønsted acids/bases, and phase-transfer organocatalysis, reflecting their increasingly important role in organic and applied chemistry.

Thiol molecules have been recently re-considered as drug candidates in viral infections because of their ability to induce redox changes which interfere with virus life cycle and modulate the host immune response. Little is known about the molecular mechanisms of their immunomodulatory properties. Here we show that I-152, a thiol molecule metabolized to release N-acetyl-l-cysteine and cysteamine and acting as a pro-glutathione agent, causes early up-regulation of immunoproteasome subunits in the lymph nodes of murine leukemia virus infected mice. This evidence suggests that the immunoproteasome may be modulated by thiol-based compounds with important implications in understanding redox-controlled immunoregulation.

A concise, convergent, and enantioselective synthesis of (−)‐6,7‐secoagroclavine, a pivotal intermediate in the synthesis of both clavine and ergot alkaloids, was accomplished from a derivative of the renowned Uhle's ketone. The synthesis is centered on metal‐free reductive coupling of the tosylhydrazone derivative of protected 4‐amino Uhle's ketone and commercially available 2,2‐dimethylethenylboronic acid, which is used as a four‐carbon building block. This novel approach directly sets the stereochemistry on the difficult‐to‐access aryl vinyl methane carbon stereogenic center of (−)‐6,7‐secoagroclavine.

The SARS-CoV-2 life cycle is strictly dependent on the environmental redox state that influences both virus entry and replication. A reducing environment impairs the binding of the spike protein (S) to the angiotensin-converting enzyme 2 receptor (ACE2), while a highly oxidizing environment is thought to favor S interaction with ACE2. Moreover, SARS-CoV-2 interferes with redox homeostasis in infected cells to promote the oxidative folding of its own proteins. Here we demonstrate that synthetic low molecular weight (LMW) monothiol and dithiol compounds induce a redox switch in the S protein receptor binding domain (RBD) toward a more reduced state. Reactive cysteine residue profiling revealed that all the disulfides present in RBD are targets of the thiol compounds. The reduction of disulfides in RBD decreases the binding to ACE2 in a cell-free system as demonstrated by enzyme-linked immunosorbent and surface plasmon resonance (SPR) assays. Moreover, LMW thiols interfere with protein oxidative folding and the production of newly synthesized polypeptides in HEK293 cells expressing the S1 and RBD domain, respectively. Based on these results, we hypothesize that these thiol compounds impair both the binding of S protein to its cellular receptor during the early stage of viral infection, as well as viral protein folding/maturation and thus the formation of new viral mature particles. Indeed, all the tested molecules, although at different concentrations, efficiently inhibit both SARS-CoV-2 entry and replication in Vero E6 cells. LMW thiols may represent innovative anti-SARS-CoV-2 therapeutics acting directly on viral targets and indirectly by inhibiting cellular functions mandatory for viral replication.

Reduction in oxygen levels is a key feature in the physiology of the bone marrow (BM) niche where hematopoiesis occurs. The BM niche is a highly vascularized tissue and endothelial cells (ECs) support and regulate blood cell formation from hematopoietic stem cells (HSCs). While in vivo studies are limited, ECs when cultured in vitro at low O2 (<5%), fail to support functional HSC maintenance due to oxidative environment. Therefore, changes in EC redox status induced by antioxidant molecules may lead to alterations in the cellular response to hypoxia likely favoring HSC self-renewal. To evaluate the impact of redox regulation, HUVEC, exposed for 1, 6, and 24 h to 3% O2 were treated with N-(N-acetyl-l-cysteinyl)-S-acetylcysteamine (I-152). Metabolomic analyses revealed that I-152 increased glutathione levels and influenced the metabolic profiles interconnected with the glutathione system and the redox couples NAD(P)+/NAD(P)H. mRNA analysis showed a lowered gene expression of HIF-1α and VEGF following I-152 treatment whereas TRX1 and 2 were stimulated. Accordingly, the proteomic study revealed the redox-dependent upregulation of thioredoxin and peroxiredoxins that, together with the glutathione system, are the main regulators of intracellular ROS. Indeed, a time-dependent ROS production under hypoxia and a quenching effect of the molecule were evidenced. At the secretome level, the molecule downregulated IL-6, MCP-1, and PDGF-bb. These results suggest that redox modulation by I-152 reduces oxidative stress and ROS level in hypoxic ECs and may be a strategy to fine-tune the environment of an in vitro BM niche able to support functional HSC maintenance.

An unusual photoredox-catalyzed radical decarboxylative cyclization cascade reaction of γ,γ-dimethylallyltryptophan (DMAT) derivatives containing unactivated alkene moieties has been developed, providing green and efficient access to various six-, seven-, and eight-membered ring 3,4-fused tricyclic indoles. This type of cyclization, which was hitherto very difficult to comprehend in ergot biosynthesis and to accomplish by more conventional procedures, enables the synthesis of ergot alkaloid precursors. In addition, this work describes a mild, environmentally friendly method to activate, reductively and oxidatively, natural carboxylic acids for decarboxylative C–C bond formation by exploiting the same photocatalyst.

The growing importance of structurally diverse and functionalized enantiomerically pure unnatural amino acids in the design of drugs, including peptides, has stimulated the development of new synthetic methods. This study reports the challenging direct asymmetric alkylation of cyclic ketones with dehydroalanine derivatives via a conjugate addition reaction for the synthesis of enantiopure ketone-based alpha-unnatural amino acids. The key to success was the design of a bifunctional primary amine-thiourea catalyst that combines H-bond-directing activation and enamine catalysis. The simultaneous dual activation of the two relatively unreactive partners, confirmed by mass spectrometry studies, results in high reactivity while securing high levels of stereocontrol. A broad substrate scope is accompanied by versatile downstream chemical modifications. The mild reaction conditions and consistently excellent enantioselectivities (>95% ee in most cases) render this protocol highly practical for the rapid construction of valuable noncanonical enantiopure a-aminoacid building blocks.

A unified enantioselective synthesis and the biological evaluation of all rugulovasine stereoisomers are reported. The syntheses are centered on the divergent and stereochemical modular combination of each enantiomer of 4-amino Uhle's ketone and a methacrylate derivative to build the unsaturated oxaspirolactone moiety by the Dreiding-Schmidt reaction, followed by Fukuyama alkylation to afford the required N-methyl secondary amine in excellent yield. The modularity of this divergent approach, the diastereoselectivities of the reactions, and the late-stage site-selective methylation permit the rapid asymmetric syntheses of all rugulovasine stereoisomers, including the first total syntheses of optically pure (+)- and (-)-rugulovasine B and their trideuteromethylated derivatives. All enantiopure stereoisomers of rugulovasine were tested for their binding affinities to dopamine, serotonin, and adrenergic neuroreceptors, revealing their preferred selectivity for the serotonin 1 A receptor.

We report the synthesis, chemical properties, and disulfide bond-reducing performance of a dithiol called NAC-MEAA, conceived as a hybrid of two biologically relevant thiols: cysteine and cysteamine. NACMEAA is conveniently prepared from inexpensive L-cystine in an efficient manner. As a nonvolatile, highly soluble, and neutral compound at physiological pH with the first thiol pKa value of 8.0, NACMEAA is reactive and user-friendly. We also demonstrate that NACMEAA reduces disulfide bonds in GSSG and lysozyme.

AbstractUhle’s ketone and its derivatives are highly versatile intermediates for the synthesis of a variety of 3,4-fused tricyclic indole frameworks, i.e. indole alkaloids of the ergot family, that are found in various bioactive natural products and pharmaceuticals. Therefore, the development of a convenient preparative method for this structural motif as well as its opportune/useful derivatization have been the subject of longstanding interest in the fields of synthetic organic chemistry and medicinal chemistry. Herein, we summarize recent and less recent methods for the preparation of Uhle’s ketone and its derivatives as well as its main reactivity towards the synthesis of bioactive substances. Regarding the preparation, it can be roughly classified into two categories: (a) using 4-unfunctionalized and 4-functionalized indole derivatives as starting materials to construct a fused six-member ring, and (b) constructing the indole ring through intramolecular cycloaddition. Principally, the reactivity of the cyclic Uhle’s ketone shown here is derived from the classical electrophilicity of the carbonyl carbon or the acidity of the α-hydrogen and, though less intensively investigated, chemical reactions that induce ring expansion to form novel ring skeletons.1 Introduction2 Synthesis2.1 Disconnection A: Cyclization Reaction of the Opportune 3,4-Disubstituted Indole2.2 Disconnection B: Intramolecular Friedel–Crafts Cyclization2.3 Disconnection B: Intramolecular Cyclization via Metal–Halogen Exchange2.4 Disconnection C: Intramolecular Diels–Alder Furan Cycloaddition2.5 Disconnection D: Intramolecular Dearomatizing [3 + 2] Annulation3 Reactivity3.1 Use of Uhle’s Ketone for Lysergic Acid3.2 Use of Uhle’s Ketone for Rearranged Clavines3.3 Use of Uhle’s Ketone for Medicinal Chemistry4 Conclusion and Outlook

A practical and asymmetric synthesis of (R)-4-amino-5-oxo-1,3,4,5-tetrahydrobenz[cd]indole, an enantiopure framework shared by most ergot alkaloids, was accomplished. Our method involves a Rh(i)-catalyzed 6-exo-trig intramolecular cyclization of an appropriate 4-pinacolboronic ester d-tryptophan aldehyde followed by the oxidation of the resulting secondary benzylic alcohol with a Cu(i)-ABNO catalyst and final deprotection under acidic conditions. This new procedure offers significant advantages over previous synthetic approaches, including brevity, mild reaction conditions, preservation of chiral integrity, and high overall yield and avoids the use of stoichiometric amounts of strongly basic and pyrophoric organometallic reagents.