Synthesis Of Organic Compounds Research Articles

Synthesis of 13C-depleted organic matter from CO in a reducing early Martian atmosphere

AbstractOrganic matter found in early Martian sediment may yield clues to the planet’s environmental conditions, prebiotic chemistry and habitability, but its origin remains unclear. Strong 13C depletion in sedimentary organic matter at Gale crater was recently detected by the Curiosity rover. Although this enigmatic depletion remains debated, if correct, a mechanism to cause such strong 13C depletion is required. Here we show from CO2 photolysis experiments and theoretical considerations that solar ultraviolet photolysis of CO2 in a reducing atmosphere can yield strongly 13C-depleted CO. We suggest that atmospheric synthesis of organic compounds from photolysis-produced CO is a plausible mechanism to explain the source of isotopically depleted organic matter in early Martian sediments. Furthermore, this mechanism could explain 13C enrichment of early Martian CO2 without requiring long-term carbon escape into space. A mass balance model calculation using our estimated isotopic fractionation factor indicates the conversion of approximately 20% of volcanic CO2 emissions on early Mars into organics via CO, consistent with the available data for carbon isotopes of carbonate. Although alternative pathways for organic compound production have been proposed, our findings suggest that considerable amounts of organic matter may have been synthesized from CO in a reducing early Martian atmosphere and deposited in sediments.

Indium Triflate's Transformative Role in Modern Organic Synthesis: A Five‐Year Survey of Functionalization, Cyclization, and Multicomponent Reactions

AbstractIndium triflate (In(OTf)3) has proven to be a powerful and sustainable catalyst in the synthesis of modern organic compounds, enabling a variety of transformations such as functionalization, cyclization, and multicomponent reactions. To provide insight into the most recent methods and applications, this study attempts to provide a comprehensive and up‐to‐date summary of these advances in the application of indium triflate as a catalyst in organic synthesis, focusing on the last five years of literature. The application of indium triflate as opposed to alternative indium(III) catalysts in organic transformations will be the main emphasis of this review, which will cover recent developments through research articles and reviews published between 2019 and 2023. This minireview will make a significant contribution to the existing literature by consolidating recent advancements in the use of indium triflate in modern organic synthesis.

Electrochemical oxidation of concentrated benzyl alcohol to high-purity benzaldehyde via superwetting organic-solid-water interfaces.

Organic electrosynthesis in aqueous media is presently hampered by the poor solubility of many organic reactants and thus low purity of liquid products in electrolytes. Using the electrooxidation of benzyl alcohol (BA) as a model reaction, we present a "sandwich-type" organic-solid-water (OSW) system, consisting of BA organic phase, KOH aqueous electrolyte, and porous anodes with Janus-like superwettability. The system allows independent diffusion of BA molecules from the organic phase to electrocatalytic active sites, enabling efficient electrooxidation of high-concentration BA to benzaldehyde (97% Faradaic efficiency at ~180 mA cm-2) with substantially reduced ohmic loss compared to conventional solid-liquid systems. The confined organic-water boundary within the electrode channels suppresses the interdiffusion of molecules and ions into the counterphase, thus preventing the hydration and overoxidation of benzaldehyde during long-term electrocatalysis. As a result, the direct production of high-purity benzaldehyde (91.7%) is achieved in a flow cell, showcasing the effectiveness of electrocatalysis over OSW interfaces for the one-step synthesis of high-purity organic compounds.

Synthesis of Benzimidazole Based 1,2,4‐Triazole Derivatives as Potential Anticancer Agents: In Silico Techniques

AbstractCompounds with a 1,2,4–triazole scaffold serve an essential role in organic synthesis, particularly in the synthesis of bioactive organic compounds; thus, the development of new approaches for modifying this scaffold is a very interesting framework of this study. To contribute to the development of an efficient method for the conversion of anticancer triazoles, a novel series of benzimidazole based 1,2,4‐triazoles was designed and synthesized. All the newly synthesized derivatives were characterized by NMR (1H &13C), FT–IR and mass spectrometry. Among the tested compounds, hybrids 5 b, 5 g exhibited exceptional anticancer susceptibilities with IC50=8.8±0.9, 9.2±1.5 μM against the tested HCA‐7cancer cell line. Anticancer profiles showed that compounds 5 d, 5 i had better anticancer inhibitory potency against a breast cancer cell line MCF‐7with IC50values 8.3±2.1, 10.6±1.2 μM, whereas 5 d, and 5 g showed potent anticancer activity against colorectal cancer cell line HT29 with IC50 values 7.1±±0.9, 7.7±1.2 μM respectively. From docking results, 5 d demonstrated highly stable binding amino acids LeuA : 2247, GlyA : 2449, SerA : 2409, HisA : 2379, AspA : 2373, LysA : 2318, IleA : 2317, IleA : 2246, IleA : 2412, AlaA : 2410, GlnA : 2452, AsnA : 2245, TyrA : 2243, and HisA : 2448, which play a crucial role enabling optimal ligand binding in a crystal structure tyrosine phosphatase mutated in colorectal cancer (PDB: 1WCH). Furthermore, the physicochemical and absorption, distribution, metabolism, and excretion (ADME) filtration molecular properties, estimation of bioactivity, and toxicity scores of these scaffolds were evaluated.

Rare‐Earth‐Metal Alkyl and Aryl Compounds in Organic Synthesis

Rare‐earth‐metal (Ln) alkyl and aryl compounds feature highly reactive, thermally labile [Ln–C] s‐bonds which result in rapid and violent decomposition in the presence of air and moisture. Nevertheless, such [Ln–C] moieties display important intermediate species in numerous organic transformations. Reagents containing [Ln–C] bonds are deliberately generated in situ like Imamoto‐type reagents Ln(III)Cl3/RLi (routinely at low temperatures) or “heavy” lanthanide‐Grignard compounds RLnX. Samarium(III)‐alkyl species are supposed intermediates of SmI2‐promoted Barbier‐type carbon– carbon coupling reactions. Alkyl/aryl ligand exchange at Ln(III) centers has been identified as the crucial step of lanthanide–halogenexchange reactions. In the meantime, several such mixed alkyl/halogenido complexes, devoid of an ancillary ligand, could be isolated and scrutinized with regard to structure and reactivity. More recently, Ln(III)‐alkylidene complexes could be accessed, structurally authenticated and successfully employed in Tebbe‐like olefination reactions of ketones.

Design of a tunable bacterial gene expression system using engineered σ factors.

The synthesis of organic compounds involves the action of multiple enzymes in a biosynthetic pathway. Incorporating such biosynthetic pathways into microbes often leads to substantial cellular and metabolic stress resulting in low titers of the target compound. This limitation can be offset, in part, by optimizing enzyme efficiency and cellular enzyme concentration. The former involves significant efforts to achieve improvements in catalytic efficiency with the caveat that the metabolic load on a microbial cell imposed by the overexpression of the exogenous enzyme could result in reduced cell fitness. Here, we demonstrate the feasibility of engineered σ factors to modulate gene expression levels without significant genetic engineering. We note that changing the sequence of two flexible polypeptide loops without any changes to the structural scaffold of the transcription initiation factor σE could modulate the expression levels of the target genes. This ability provides a route to improve the efficiency of a biosynthetic pathway without altering the overall genomic makeup. The σE chimera library thus provides an avenue for pre-determined conditional gene expression of specific genes in Escherichia coli.

Applications of Transition Metal-Catalyzed ortho-Fluorine-Directed C-H Functionalization of (Poly)fluoroarenes in Organic Synthesis.

The synthesis of organic compounds efficiently via fewer steps but in higher yields is desirable as this reduces energy and reagent use, waste production, and thus environmental impact as well as cost. The reactivity of C-H bonds ortho to fluorine substituents in (poly)fluoroarenes with metal centers is enhanced relative to meta and para positions. Thus, direct C-H functionalization of (poly)fluoroarenes without prefunctionalization is becoming a significant area of research in organic chemistry. Novel and selective methodologies to functionalize (poly)fluorinated arenes by taking advantage of the reactivity of C-H bonds ortho to C-F bonds are continuously being developed. This review summarizes the reasons for the enhanced reactivity and the consequent developments in the synthesis of valuable (poly)fluoroarene-containing organic compounds.

Recent Advances and Challenges in Electrocatalytic Carboxylation of CO2

AbstractThe electrochemical fixation of carbon dioxide onto organic matter has emerged as a promising approach in recent years. By combining the unique features of electrochemistry with the goal of carbon dioxide fixation, researchers aim to develop new strategies that can contribute to a more sustainable and environmentally friendly synthesis of organic compounds. One advantage of electrochemical methods is their ability to provide both electrons and energy for chemical transformations. This allows for the direct conversion of carbon dioxide into valuable organic products, without the need for transition metal catalysts or harsh reaction conditions. As a result, electrochemical carbon dioxide fixation offers the potential for milder and more efficient processes compared to traditional methods. Scientists have made noteworthy progress in exploring different strategies for the fixation of carbon dioxide under electrochemical conditions. These strategies involve the activation of various types of chemical bonds, including C(sp2)–C(sp2), C(sp2)–H, C–X (X = halogen), and C(sp3)–X (X = S, C, O, N). This review aims to provide an overview of the current state of research on electrochemical carbon dioxide fixation into organic matter. It will discuss the different strategies employed, the key findings, and the challenges that remain to be addressed. By highlighting the recent advancements in this field, this review hopes to inspire further exploration and innovation in the area of electrochemical synthesis for carbon dioxide fixation.1 Introduction2 Electrocatalytic Monocarboxylation of CO2 2.1 Monocarboxylation of C(sp2)–C(sp2)2.2 Monocarboxylation of C(sp2)–H2.3 Monocarboxylation of C–X (X = Cl, Br, I)2.4 Monocarboxylation of C(sp3)–X (X = S, C, O, N)3 Electrocatalytic Dicarboxylation of CO2 4 Electrocatalytic Esterification of CO2 5 Conclusions

Generation and Application of Aryl Radicals Under Photoinduced Conditions.

Photoinduced aryl radical generation is a powerful strategy in organic synthesis that facilitates the formation of diverse carbon-carbon and carbon-heteroatom bonds. The synthetic applications of photoinduced aryl radical formation in the synthesis of complex organic compounds, including natural products, physiologically significant molecules, and functional materials, have received immense attention. An overview of current developments in photoinduced aryl radical production methods and their uses in organic synthesis is given in this article. A generalized idea of how to choose the reagents and approach for the generation of aryl radicals is described, along with photoinduced techniques and associated mechanistic insights. Overall, this article offers a critical assessment of the mechanistic results as well as the selection of reaction parameters for specific reagents in the context of radical cascades, cross-coupling reactions, aryl radical functionalization, and selective C-H functionalization of aryl substrates.

Microwave Assisted Groebke-Blackburn-Bienayme Multicomponent Reaction to Synthesis of Imidazo[1,2-a]pyridine-furan Hybrids as Possible Therapeutic Option for Leukemia, Colon Cancer and Prostate Cancer

aims: Microwave assisted ecofriendly catalytic protocol for the Groebke-Blackburn-Bienayme multicomponent reaction to synthesis imidazo[1,2-a]pyridine-furan hybrids as possible therapeutic option for leukemia, colon cancer and prostate cancer background: Microwave synthesis has emerged as a potent tool for the more economical and environmentally friendly synthesis of organic compounds, such as derivatives of imidazo[1,2-a]pyridine. Compared to traditional synthesis, microwave radiation causes molecules to be excited and distributes thermal energy evenly in a shorter amount of time. Shorter response times and generally improved efficiency are the benefits of this. objective: The primary objective of the work presented in this article was to prepare imidazo[1,2-a]pyridine-furan hybrids via Groebke-Blackburn-Bienayme multicomponent reaction using PEG 400 in microwave irradiation as green approach. characterized their anticancer activities against leukemia, colon cancer and prostate cancer are evaluated. method: In a sealed microwave glass vial, 5-methylfuran-2-carbaldehyde 1, 2-aminoazines 2a-g, isocyanides 3a-c in presence of 20mol result: We have successfully synthesised the imidazo[1,2-a]pyridine-furan hybrids via Groebke-Blackburn-Bienayme multicomponent reaction using PEG 400 in microwave irradiation as green approach. The structures of the compounds were confirmed through various spectroscopic techniques. Characterized their anticancer activities against leukemia, colon cancer and prostate cancer are evaluated. conclusion: The reported protocol is advantageous over conventional methods of imidazo[1,2-a]pyridine derivatives. The time required for the reaction is much less as compared to the usual requirements of reflux. Compound 4e, 4f, 4n and 4o shows the most increased activity against cell line RPMI-8226, HCT-116 and PC-3 of Leukemia, Colon cancer and Prostate cancer respectively. By using the potential of imidazo[1,2-a]pyridine-furan based compounds via sustainable green approach, more effective and accurate cancer treatments can be designed in future. other: NA

1-(3,4-Dimethoxyphenyl)-3-(4-methoxyphenyl)-3-(1H-1,2,4-triazol-1-yl)propan-1-one

The study of new catalytic protocols for the synthesis of organic compounds with a more sustainable perspective is of interest. The use of ionic organic solids, such as 1,3-bis(carboxymethyl)imidazolium chloride as a catalyst has allowed the Michael addition of N-heterocycles to chalcones. This methodology has been applied to the unique preparation of the potential bioactive compound 1-(3,4-dimethoxyphenyl)-3-(4-methoxyphenyl)-3-(1H-1,2,4-triazol-1-yl)propan-1-one with moderate yield, due to the retro-Michael reaction. Both synthetic reactions (i.e., preparation of chalcone and triazole Michael-addition to chalcone) have good green metrics.

Mid-Long Chain Dicarboxylic Acid Production via Systems Metabolic Engineering: Progress and Prospects.

Mid-to-long-chain dicarboxylic acids (DCAi, i ≥ 6) are organic compounds in which two carboxylic acid functional groups are present at the terminal position of the carbon chain. These acids find important applications as structural components and intermediates across various industrial sectors, including organic compound synthesis, food production, pharmaceutical development, and agricultural manufacturing. However, conventional petroleum-based DCA production methods cause environmental pollution, making sustainable development challenging. Hence, the demand for eco-friendly processes and renewable raw materials for DCA production is rising. Owing to advances in systems metabolic engineering, new tools from systems biology, synthetic biology, and evolutionary engineering can now be used for the sustainable production of energy-dense biofuels. Here, we explore systems metabolic engineering strategies for DCA synthesis in various chassis via the conversion of different raw materials into mid-to-long-chain DCAs. Subsequently, we discuss the future challenges in this field and propose synthetic biology approaches for the efficient production and successful commercialization of these acids.

Impact of Pickering Emulsions Composition on Lipase Catalyzed Peroxyacetic Acid Synthesis

AbstractDue to the need for environmental protection and sustainability, there has been a rising need to replace the traditionally harsh oxidative functionalization process, which is essential for syntheses of various organic compounds, by biocatalysis. However, the investigated alternative processes are still challenged with enzyme instability and/or low specific reaction rate. Due to these still existing challenges and the recognition of Pickering emulsions as an efficient platform for continuous biphasic biocatalysis, the first, enzymatic step of the lipase catalyzed oxidative functionalization was investigated in bioactive Pickering emulsions. The study focused on the impact of Pickering emulsion composition such as the volume phase fraction, type and concentration of the nanoparticles and enzymes on continuous peroxyacetic acids synthesis. The type of nanoparticles used and Candida antarctica lipase B concentration significantly impacted the process while the other named parameters only had a marginal influence.

Modification of nitrilase based on computer screening and efficient biosynthesis of 4-cyanobenzoic acid.

4-cyanobenzoic acid serves as a crucial intermediate for the synthesis of various high-value organic compounds. The enzymatic hydrolysis of terephthalonitrile to produce 4-cyanobenzoic acid using nitrilase offers the advantages of a simple reaction pathway, environmental friendliness, and easy product separation. In order to efficiently develop nitrilases that meet industrial production requirements, the virtual screening method used in the study is established and mature. From a total of 371 amino acids in the nitrilase AfNIT, which exhibits activity in terephthalonitrile hydrolysis, three candidate sites (F168, S192, and T201) were identified, and a "small and accurate" mutant library was constructed. The triple mutant F168V/T201N/S192F was screened from this small mutant library with a specific activity of 227.3 Umg-1 , which was 3.8 times higher than that of the wild-type AfNIT. Using the whole-cell biocatalyst containing the mutant F168V/T201N/S192F, terephthalonitrile was successfully hydrolyzed at a concentration of 150gL-1 to produce 4-cyanobenzoic acid with a final yield of 170.3gL-1 and a conversion rate of 98.7%. The obtained nitrilase mutant F168V/T201N/S192F in this study can be effectively applied in the biomanufacturing of 4-cyanobenzoic acid using terephthalonitrile as a substrate. Furthermore, the results also demonstrate the significant improvement in predictive accuracy achieved through the latest AI-assisted computer simulation methods. This approach represents a promising and feasible new technological pathway for assisting enzyme engineering research, laying a theoretical foundation for other related studies.

Catalyst Selection over an Electrochemical Reductive Coupling Reaction toward Direct Electrosynthesis of Oxime from NOx and Aldehyde.

Aqueous electrochemical coupling reactions, which enable the green synthesis of complex organic compounds, will be a crucial tool in synthetic chemistry. However, a lack of informed approaches for screening suitable catalysts is a major obstacle to its development. Here, we propose a pioneering electrochemical reductive coupling reaction toward direct electrosynthesis of oxime from NOx and aldehyde. Through integrating experimental and theoretical methods, we screen out the optimal catalyst, i.e., metal Fe catalyst, that facilitates the enrichment and C-N coupling of key reaction intermediates, all leading to high yields (e.g., ∼99% yield of benzaldoxime) for the direct electrosynthesis of oxime over Fe. With a divided flow reactor, we achieve a high benzaldoxime production of 22.8 g h-1 gcat-1 in ∼94% isolated yield. This work not only paves the way to the industrial mass production of oxime via electrosynthesis but also offers references for the catalyst selection of other electrochemical coupling reactions.

High pressure Raman study of isobutyramide

Isobutyramide (IBA) has attracted considerable attention due to its expansive prospects for practical applications in the synthesis of drugs, dyes and other organic compounds. Herein we perform the high-pressure studies of IBA crystal by Raman spectral measurements at room temperature from ambient pressure to 30 GPa by using diamond anvil cells (DACs) to gain comprehensive insights into its structure and stability. Raman vibrational modes of IBA crystal at ambient pressure are resolved based on the experimental results and the first-principles theoretical calculations. High-pressure Raman scattering results show the Raman bands splitting, emergence/disappearance of the Raman bands and discontinuous wavenumber shifts at 1, 2 and 10 GPa, which indicate that IBA crystal undergoes three structural phase transitions at corresponding pressure. In addition, softening of the C = O and N–H stretching vibrational modes of IBA with increasing pressure can be interpreted by the reorganization of the hydrogen bond network of IBA molecules due to phase transition.

Carboiodanation of Arynes: Organoiodine(III) Compounds as Nucleophilic Organometalloids.

Organic iodine(III) compounds represent the most widely used hypervalent halogen compounds in organic synthesis, where they typically perform the role of an electrophile or oxidant to functionalize electron-rich or -nucleophilic organic compounds. In contrast to this convention, we discovered their unique reactivity as organometallic-like nucleophiles toward arynes. Equipped with diverse transferable ligands and supported by a tethered spectator ligand, the organoiodine(III) compounds undergo addition across the electrophilic C-C triple bond of arynes while retaining the trivalency of the iodine center. This carboiodanation reaction can forge a variety of aryl-alkynyl, aryl-alkenyl, and aryl-(hetero)aryl bonds along with the concurrent formation of an aryl-iodine(III) bond under mild conditions. The newly formed aryl-iodine(III) bond serves as a versatile linchpin for downstream transformations, particularly as an electrophilic reaction site. The amphoteric nature of the iodine(III) group as a metalloid and a leaving group in this sequence enables the flexible and expedient synthesis of extended π-conjugated molecules and privileged biarylphosphine ligands, where all of the iodine(III)-containing compounds can be handled as air- and thermally stable materials.

Organic Synthesis via Renewable Heterogeneous Nanocatalysts Based on Montmorillonite Clay

Abstract: Synthetic organic molecules are vital for human life, serving as medications, pesticides, dyes, and food additives. Organic synthesis provides routes for the production of these molecules. The traditional methods of organic synthesis require energy, solvents, time, and certain conditions based on the nature of the reactions. To address the issues associated with conventional processes, various environmentally friendly (green) methodologies have been developed. Catalysts are crucial in many chemical methods. Chemists aim to develop catalysts that are cost-effective, easy to recover, and can be synthesized with high catalytic activity and renewability. Natural montmorillonite clay is an ideal material for efficient catalysts since it satisfies all these requirements. This review focuses on the recent advances in the development of renewable nanocatalysts made from montmorillonite to be used for the synthesis of various organic compounds.

One-pot Multicomponent Synthesis of Hydrazinyl Thiazoles Bearing an Isatin Moiety in Aqueous Medium

Abstract: Isatin-derivatives are an important class of nitrogen-containing heterocyclic compounds in organic synthesis. On the other hand, 1,3-thiazoles are 5-membered heterocyclic compounds containing nitrogen and sulphur atoms. Hydrazinyl thiazoles are often prepared through the classical condensation of aldehydes or ketones with thiosemicarbazide to yield thiosemicarbazones, which will then undergo heterocyclization with phenylacyl bromides to give the corresponding hydrazinyl thiazoles. Nowadays, multi-component reactions (MCRs) are considered the most powerful tool in organic synthesis. The use of water as a green solvent in organic synthesis is one of the goals of green chemistry. In this study, a series of new hydrazinyl thiazoles 3a-3u bearing an isatin moiety were synthesized in good yield via a one-pot three-component condensation reaction of isatins with thiosemicarbazide and phenyl acyl bromides in water under reflux condition. All the synthesized compounds were characterized by IR, 1D-NMR, 2D-NMR and LC/MS spectral data.

Multicomponent Synthesis of Structurally Diverse Spiroheterocycles using Bio-organic Catalyst in Aqueous Medium

Background: MCRs are one of the most significant tools in the synthesis of organic compounds. MCR is a rapid chemical technique that uses three or more reactants to produce products that sustain all structural and substructural properties of the initial components. MCRs are useful in all fields of synthetic chemistry because of their rapid rate of reaction, simple procedure and excellent yields. We reported an efficient and environmentally friendly domino approach for the synthesis of spiroheterocycles spiro annulated with indeno[1,2-b]quinoline. background: The spirooxindole scaffold has a significant structural role in several bioactive organic substances and pharmaceuticals like spirotryprostatin A and B, coerulescine, pteropodine horsfiline, alstonisine, elacomine, and rhynchophylline.5 Spiro heterocycle molecules, which have two rings that share a sp3 carbon atom, are key frameworks in pharmaceutical chemistry. They can be found in a wide range of both organic and synthetic materials as well as have several properties because of the rigidity and complexity of their structural design. Furthermore, spiroxindole is used as a key component in numerous medicines such as anticancer, antibacterial, antiviral, and inhibitors of the human NK-1 receptor Method: The spiroheterocycles with privileged heterocyclic substructures have been synthesized using taurine (2-aminoethanesulfonic acid) as a green, sustainable, bio-organic and recyclable catalyst in a three-component reaction of isatins, 1,3-diketones, and 1-napthylamine in aqueous media. The present synthetic method is probably the first report to synthesize spiroheterocycles, spiroannulated with indeno[1,2-b]quinoline. Furthermore, the approach is valuable because of the excellent yield that results from the reaction in 15-20 min. Result: The optimization of reaction conditions is an important case of efficient synthesis. The solvent, temperature, time and catalyst loading were all examined. The reusability of the catalyst was also investigated experimentally. The used catalyst taurine has a high activity as well as good reusability. The present synthetic protocol will be extended to synthesise a library of hybrid compounds. The present synthetic approach is cost-effective, and time-efficient with an easy-workup methodology that gives outstanding yields (80–95%) in 15–20 min. Conclusion: Taurine-catalyzed multicomponent reaction is a novel and efficient method for the synthesis of spiroannulated indeno[1,2-b]quinolines. The high catalytic activity of taurine as a catalyst with water as a green solvent makes the process environmentally friendly. The special features of the synthetic protocol include synthetic efficiency, operational simplicity, and reusability of the catalyst and it is expected to make significant contributions not only to drug discovery studies but also to pharmaceutical and therapeutic chemistry in view of introducing molecular diversity in the synthesized molecules. result: The current synthetic technique has various distinct characteristics, including simple procedure, high atom economy, mild reaction conditions and significant synthetic efficiency. The current synthesis method has been proposed to have contributed to the first report on the synthesis of spiroheterocycles with such a novel combination of preferred heterocycles employing taurine as a green bio-organic, reusable and easily recyclable catalyst. The benefits of this method include beneficial conditions in the environment, excellent purity that may be achieved without the need for column chromatography, and a reusable catalyst.