This article describes an efficient acid-catalyzed cyclization strategy for constructing the tricyclic pyrimido[1,2-a]purin-10(3H)-one scaffold via the reaction of guanine derivatives with 1,1,3,3-tetramethoxypropane (TMOP) catalyzed by 2,4,5-trifluorobenzoic acid. The method features mild conditions, eliminates the need for hydroxyl protection, and exhibits excellent functional-group tolerance, making it applicable to the late-stage structural diversification of various nucleosides, nucleotides, and oligonucleotides. Using the antiviral drug acyclovir and an azide-containing guanosine derivative as model substrates, we successfully synthesized a tricyclic acyclovir analogue in 81% yield and an M1G-containing oligonucleotide in 40% yield. This protocol provides a general, convenient, and efficient experimental approach for synthesizing this class of potentially bioactive tricyclic nucleoside analogues. © 2026 Wiley Periodicals LLC. Basic Protocol 1: Synthesis of tricyclic acyclovir analogue Basic Protocol 2: Synthesis of M1G-containing oligonucleotide.

A copper-catalyzed C2 sulfenylation of 2,3-dialkoxyindolines with N-thiosuccinimides affords 2-thio-3-alkoxyindoles under mild conditions. The CuBr2-catalyzed method tolerates aryl, alkyl, cysteinyl, and glycosyl thiolating agents, via a 3-alkoxyindole intermediate, providing direct access to S-linked indole glycosides related to the hair growth promoter Calanthoside.

An efficient copper-catalyzed thioglycosylation of tryptophan and tryptophan-containing peptides with N-(thioglycosyl)succinimide has been developed. The methodology demonstrates broad substrate compatibility, encompassing diverse glycan donors (hexoses, pentoses, and disaccharides) and peptide backbones (di-, tri-, and tetrapeptides). Furthermore, the protocol was extended to S-arylation, S-alkylation, cysteinylation, thiocyanation, and selenoarylation, showcasing its versatility.

An anion-switch strategy employing a hypervalent iodine/protic acid system achieves programmable pathway bifurcation following pyrimidine dearomatization. Changing the acid counterion precisely diverts the reaction trajectory: triflic acid promotes ring-contractive dearomatization to imidazolines, whereas hydrogen halides trigger ring-retentive dearomatization to halogenated hydropyrimidines. DFT calculations reveal that a conformationally congested hypervalent iodine intermediate constitutes the mechanistic bifurcation point. Halide anions kinetically trap this intermediate through low-barrier transition states, diverting the reaction from the ring-contractive to the ring-retentive pathway.

Indole S-glycosides are a class of natural products in which an indole scaffold is connected to a glycosyl unit via a sulfur atom, forming a rare C-S glycosidic bond. These compounds have attracted considerable attention due to their unique chemical properties and diverse biological activities, including antiviral, anti-inflammatory, and anti-photoaging activities. This review systematically summarizes the discovery history, structural characteristics, and chemical synthesis of naturally occurring indole S-glycosides. We outline the trajectory from the discovery of calanthoside to the systematic isolation of indole S-glycosides from Isatis indigotica, classify three structural types based on the original literature nomenclature-isatindigotindolosides (Type I), isatindigobisindoloside (Type II), and isatigotindolediosides (Type III)-and discuss their bioactivities. We then focus on advances in C-S bond construction strategies for thioglycosylated indoles, including copper-catalyzed, TMSOTf-catalyzed, iodine-catalyzed, nickel-catalyzed, and photoredox-catalyzed methods. Finally, we describe the application of these methods to the total syntheses of calanthoside and isatindigotindolosides I-III and isatigotindoledioside E.

In the realm of molecular construction, the skeletal editing techniques of heterocyclic compounds demonstrate unique efficiency, particularly in synthesizing molecular structures that are challenging to obtain through traditional synthetic methods. Compared to the ring-contraction reaction of saturated nitrogen heterocycles and aryl rings, the site selectivity and stereoselective skeletal editing of pyrimidine fused heterocycles remain relatively underdeveloped. Here we report a chiral hypervalent iodine(III)-catalyzed skeletal editing of pyrimidine moieties within polynitrogen heterocycles, which efficiently produces optically pure multi-substituted imidazoline rings. The reaction demonstrates exceptional functional group tolerance, as shown by the ring contraction of diverse polynitrogen heterocycles and the late-stage functionalization of M1G-dR and its analogues, including nucleosides, nucleotides, and oligonucleotides. Density functional theory calculations explore the details of the mechanism and the factors that determine the reaction's stereoselectivity.

An efficient iodine-catalyzed thioglycosylation reaction for the synthesis of indole thioglycosides and S-glycosylated peptides is reported. This method employs molecular iodine as a metal-free catalyst and thioglycosides as sulfur donors, achieving high yields (up to 97%) under mild conditions. The reaction is compatible with a broad range of substrates, including various monosaccharide-derived thioglycosides and indoles with different substituents. Additionally, the method is successfully applied to the functionalization of tryptophan-containing peptides, yielding thioglycopeptide derivatives in moderate to good yields. The study not only expands the synthetic accessibility to S-linked glycopeptides but also provides a valuable approach for peptide functionalization in glycochemistry.

The normal immune system maintains a dynamic equilibrium of immune regulation. When natural immune tolerance is disrupted, aberrant immune activation occurs, which leads to tissue damage and the onset of autoimmune diseases (AIDs). Pathological damage in AIDs stems from abnormal immune responses triggered by a systemic imbalance, and modern medicine has yet to find a definitive cure. The advantages of Chinese medicine (CM), which targets the fundamental pathogenesis of "immune imbalance" by regulating immune homeostasis and restoring a healthy Yin-Yang equilibrium state, are increasingly being demonstrated. CM promotes immune balance by modulating CD4[Formula: see text] T cell subset imbalances, dysfunctional immune cells (e.g., B cells, dendritic cells, and macrophages), and their associated cytokines and transcription factors. Although CM shows therapeutic potential for AIDs via immune homeostasis modulation, comprehensive reviews analyzing this approach through the lens of AIDs' shared mechanism - immune imbalance - remain scarce. Thus, this paper first elucidates immune imbalance in AIDs from the perspectives of immune cells, cytokines, and transcription factors. Then, leveraging CM's strengths in immune regulation, we systematically review current research on bioactive components extracted from Chinese herbs, such as Paeoniflorin-6'-O-benzene sulfonate (from Paeonia lactiflora) and Artesunate (from Artemisia annua), as well as herbal formulas like Zengye Runzao decoction and Er Miao San, to focus on their immunomodulatory effects in AIDs treatment. This synthesis provides valuable insights into the scientific rationale of CM for restoring immune balance in the treatment of AIDs.

Herein, a visible-light-promoted 9-thioxanthone-catalyzed cascade cyclization reaction to synthesize sulfonylated spiro-trienones, coumarins and their derivatives in yields of up to 98% under mild irradiation reaction conditions is reported. Furthermore, extensive studies, including gram-scale, radical capture, isotope and DFT experiments, were performed to gain insights into the possible reaction mechanism.

Herein, a visible-light-driven and nickel (II) catalyzed Csp-S radical cross coupling reaction to prepare sulfonyl acetylenes via phenylsulfinyl is reported. The reaction conditions are established as the combination of (PhSO2Na) (0.1 mmol, 1.0 equiv.), 2-bromoethynyl-tri(propan-2-yl)silane (0.15 mmol, 1.5 equiv.), 9-fluorenone (0.02 mmol, 0.2 equiv.), NiCl2 center dot DME (0.02 mmol, 0.2 equiv.), dtbbpy (0.025 mmol, 0.25 equiv.) in CH3CN (2.0 mL, 0.05 M) and exposed to a 23 W white LEDs under a nitrogen atmosphere with yields up to 94%. Both substrates bearing electron-rich groups and electron-poor groups can provide desired sulfonyl acetylenes. The substrate scope evaluation demonstrates the broad compatibility of this method with various substrates. Extensive studies, including control experiments and radical scavenger experiments showed that the reaction involves radical species. 8 triazole compounds were also successfully prepared via Rh(I) catalyzed "Click Reaction" with obtained sulfonyl acetylene products. The reaction is initiated with formation of benzenesulfonyl radicals under oxidation of the excited-state photosensitizer 9-fluorenone. Simultaneously, a radical addition reaction between brominated yne and Ni (0) through oxidation addition occurs, which subsequently produces Intermediate product Int-6 via oxidation addition with benzenesulfonyl radicals. Reduction elimination of intermediate Int-6 results in the final coupling product 3a.

This article is devoted to calculating the form factors of B_c → D^*, B_c → D, B_c → D_s^* and B_c → D_s transitions in the framework of three-point QCD sum rules. In QCD side the vacuum condensates up to 6-dimension are taken into account. With the obtained form factors, the decay widths and branching ratios of several two-body nonleptonic decay processes B_c →η_c D^*, η_c D, J/ψ D^*, J/ψ D, η_c D_s^*, η_c D_s, J/ψ D_s^* and J/ψ D_s are predicted. These results about the form factors and decay properties of B_c meson provide useful information for us to study the heavy-quark dynamics.

A TMSOTf-catalyzed C2-sulfenylation of indole alkaloids with N-sulfenylsuccinimides has been developed. This straightforward, metal-free, and cost-effective catalytic system produces valuable 2-thioindole derivatives with yields ranging from moderate to excellent. The synthetic applicability demonstrated includes the total syntheses of isatindigotindolosides I-IV.

Disclosed herein is a rhodium(III)-catalyzed intramolecular cyclization of ynamides with propargyl esters. A variety of highly functionalized 2,5-dihydropyrroles were obtained in moderate to good yields with high E/Z selectivities. Subsequent oxidation of the products gave valuable pyrrole derivatives. Additionally, scale-up reactions and late-stage derivatizations highlight the potential synthetic utility of this methodology.

Herein, a novel cascade gold(I)-catalyzed hydroarylation of alkynylindoles and subsequent Diels-Alder cycloaddition with electron-deficient alkynes and alkenes is described. A variety of azepino-fused hydrocarbazoles and carbazoles were obtained in moderate to excellent yields. Key features of this methodology are low catalyst loadings, high regioselectivity, broad functional group tolerances, access to important heterocycles, and 100% atom economy.

Pyrrolocarbazole skeletons are well known to possess a variety of biological activities that might be therapeutically useful in the treatment of cancers. Herein, an acid-catalyzed stereoselective hydroarylation/Diels-Alder cycloaddition/aromatization of ynamide-indoles is described. We newly designed and synthesized a variety of piperazine-fused pyrrolocarbazole derivatives that could be further applied to the synthesis of potent Wee1 inhibitors.

We report here the synthesis of tricyclic nucleoside analogues via acid-catalyzed cyclization of guanine with 1,1,3,3-tetramethoxypropane. The method enables the use of hydroxyl-unprotected antiviral drugs (acyclovir, ganciclovir, and penciclovir), guanosines, oligonucleotide, and triazole-linked nucleoside dimers as substrates. Nucleoside trimer and tetramer were synthesized by derivatization reactions.

An efficient method to construct 4-aryl-substituted β-carbolines from indole-2-methyl-α-aminoketones via a TMSOTf-promoted annulation reaction was reported. High yield along with wide substrate scope and functional group tolerance make this reaction applicable to build various highly potential bioactive β-carboline derivatives.

Despite the importance of nucleosides and nucleotides for drug discovery, only a few practical methods to prepare tricyclic nucleosides have been reported. Here, we describe a synthetic strategy for late‐stage functionalization of nucleosides and nucleotides via chemo‐ and site‐selective acid‐promoted intermolecular cyclization. The nucleoside analogs with an additional ring were obtained in moderate‐to‐high yields, including some antiviral drugs (acyclovir, ganciclovir, and penciclovir) derivatives, endogenous fused ring nucleoside (M1dG) and its derivatives, and nucleotide derivatives. © 2023 Wiley Periodicals LLC.

A rhodium(iii)-catalyzed redox-neutral spiroannulation approach to access the spiro[benzo[b][1,4]oxazine-benzo[c]chromene skeleton is described in this contribution. A variety of spiro[5.5]-heterocyclic scaffolds were obtained in moderate to excellent yields under mild conditions. Key features of this protocol are good substrate scope, silver-free conditions, low catalyst loadings, easy handling under air and 100% atom economy. Furthermore, scale-up reactions and late-stage derivatizations highlight the potential synthetic utility of this methodology.

A novel palladium(II)-catalyzed intramolecular [2 + 2 + 2] annulation of indolyl 1,3-diynes is described in this contribution. A variety of azepino-fused carbazoles are obtained in moderate to excellent yields. The key to the success of this transformation is the use of a carboxylic acid as an additive. This protocol features broad functional group tolerances, easy handling in air, and 100% atom economy. Furthermore, scale-up reactions, late-stage derivatizations, and photophysical property investigations highlight the potential synthetic utility of this methodology.