Synthesis Of Pyrazines Research Articles

Characterizing the Contribution of Strain Specificity to the Microbiota Structure and Metabolites of Muqu and Fresh High-Temperature Daqu

In this study, the differences in physicochemical properties, microbial community structure, and metabolic characteristics between various fortified Muqu and their corresponding high-temperature Daqu (HTD) were investigated using multiphase detection methods. The results demonstrated that the physicochemical properties, community structure, dominant bacterial composition, and metabolic components varied significantly among the different types of fortified HTD. The differences between HTDs became more pronounced when fortified HTD was used as Muqu. Compared to HTD, Muqu exhibited a more complex volatile profile, while HTD contained higher levels of characteristic non-volatile components. The cultivable bacteria count in Muqu was significantly higher than that in HTD, while the cultivable fungi count was slightly lower than that in HTD. The fungal profiles in HTD were primarily associated with starch hydrolysis and ethanol synthesis, while bacterial activity was more prominent in Muqu. Additionally, pyrazine synthesis was mainly attributed to fungi in Muqu and bacteria in HTD. Source Tracker analysis indicated that 8.11% of the bacteria and 26.76% of the fungi originated from Muqu. This study provides a theoretical foundation for the controlled production of HTD, contributing to improvements in its quality and consistency.

Rare taxa as the microbial taxa more sensitive to environmental changes drive alterations of daqu microbial community structure and function

Microbial interactions and environmental conditions determine the evolution of microbial communities and their functions during Nongxiangxing daqu (daqu) fermentation. In this study, the sensitivity of rare microbial taxa, conditionally rare-abundant microbial taxa and abundant microbial taxa, to environmental changes, as well as the impact of their presence on the microbial community structure and function during daqu fermentation were elucidated by using high-throughput sequencing technology combined with environmental and volatile metabolites analysis. The results indicated that rare taxa, which were the predominant microbial taxa, were more heterogeneous during the daqu fermentation process. It is necessary to note that rare taxa were more sensitive to changing environmental conditions. The microbial molecular ecological network and within-module connectivity and among-module connectivity analysis showed that most of the key nodes (∼63% of operational taxonomic units) located in the networks determining microbial interactions belong to rare taxa. Furthermore, rare taxa were significantly associated with more volatile metabolites, and rare taxa were particularly important for the synthesis of pyrazines and alcohols. The present study demonstrated that rare taxa, as the microbial taxa more susceptible to environmental variation, drive alterations in the structure of microbial communities and their functions.

Elemental Sulfur-Mediated Synthesis of Quinoxalines from Sulfoxonium Ylides.

A novel straightforward and catalyst-free approach for synthesizing quinoxaline derivatives from sulfoxonium ylides and o-phenylenediamines mediated by elemental sulfur has been described. Due to the simple and mild reaction conditions, the sulfoxonium ylides and o-phenylenediamines decorated with different functional groups furnished moderate to high yields of quinoxaline derivatives and were well tolerated. Finally, large-scale reactions, the synthesis of pyrazines, and some bioactive compounds are used to illustrate the potential utility of the developed approach.

Advances in the Synthesis and Bio-Applications of Pyrazine Derivatives: A Review

Heterocycles are significant class of compound in organic chemistry, due to their substantial pharmacological application and development of new materials, as well as their prevalence in natural products. Pyrazine is one of the most essential types of N-heterocycles, which is a useful compound in organic chemistry and has a wide range of commercial applications. It has recently been the focus of a number of techniques, owing to its widespread use as a framework in the synthesis of bioactive components, catalysts, and reactions in various media. Pyrazine compounds comprise a variety of pharmacological action, including antipyretic, anti-inflammatory, analgesic, anticancer, antibacterial, and antioxidant activity. It can be used to carry out different types of coupling reaction i.e., Suzuki, Buchwald Hartwig, oxidative coupling reactions. This review aims to summarize the recent work done pyrazine synthesis and the latest report of the last six years going in the field of pyrazine synthesis.

Catalytic Synthesis of Pyrazine and Ketone Derivatives by Unsymmetrical Triazolyl-Naphthyridinyl-Pyridine Copper

Catalytic Synthesis of Pyrazine and Ketone Derivatives by Unsymmetrical Triazolyl-Naphthyridinyl-Pyridine Copper

High-intensity ultrasound promoted the aldol-type condensation as an alternative mean of synthesizing pyrazines in a Maillard reaction model system of D-glucose-13C6 and L-glycine

This study evaluated how the generation of pyrazines was promoted by high-intensity ultrasound (HIU) in a Maillard reaction (MR) model system of glucose-glycine. Carbohydrate module labeling (CAMOLA) technique was adopted using D-glucose-13C6 to elucidate the carbon skeleton of both intermediate and final MR products (MRPs). In the D-glucose-13C6-glycine HIU-MR model system, the concentration of 11 types of pyrazines was significantly higher than their counterparts in the thermal MR. Results of CAMOLA analysis showed that a significantly lower proportion of [M]+ in pyrazines with long-length side chains was observed when compared with the pyrazines generated in thermal MR. This phenomenon may suggest the aldol-type condensation was promoted by the HIU, which is a conversion from pyrazines with short-length side chains to those with long-length side chains involving carbonyl compounds. Furthermore, the analysis of isotopomers distribution in 2,3-dimethyl-quinoxaline as the o-phenylenediamine-derivatized 2,3-butanedione indicated that the increased proportion of [M + 4]+ in 2,3-dimethyl-quinoxaline (15.74% ± 0.11%) was attributed to a cleavage of D-glucose-13C6 promoted by the HIU. The above-mentioned findings elucidate that the aldol-type condensation and cleavage of D-glucose contribute to the promoted synthesis of pyrazines. The HIU would generate an extremely high temperature and pressure environment that is favored by the aldol-type condensation as a high-pressure favored reaction. The HIU, therefore, can be further developed as a promising technique to promote flavor generation through the MR.

Onion extract catalyzed novel synthesis of pyrazine

An efficient catalytic system for analyzing Pyrazine derivatives using an extract of onion at room temperature is discussed in this research study. A very good to excellent yields in reasonably short reaction time, high atom economy, usage of readily available starting material, operational simplicity and easy workup are the fundamental features of this protocol. The versatility our method is determined by synthesizing a large number of pyrazine derivatives with (85-96%) good yield.

Synthesis of pyrazines and imidazoles using lemon juice (Citrus limon) as a recyclable catalyst

One-pot four component synthesis of 2,5,6-triaryl pyrazines, 1,2,4,5-tetraaryl imidazoles and 2,2,4,5-tetraaryl imidazoles have been achieved from benzoin, aryl amine, ammonium acetate and aryl ketone /aryl aldehydes using lemon juice (Citrus limon) as an ecofriendly catalyst in good yield under mild conditions. The antibacterial action exhibited by the synthesized compounds against clinical isolates obtained from urinary tract catheters of infected patients is close to the standard drug tetracycline. Recovery of lemon juice after completion of reaction eliminates the need to handle side products, making this process more safe and user friendly.

Pyrazines: Synthesis and Industrial Application of these Valuable Flavor and Fragrance Compounds

AbstractAlkyl pyrazines—other than being extracted from various natural sources such as coffee beans, cocoa beans, and vegetables—can be synthesized by chemical methods or by certain microorganisms. The importance of pyrazines for the food industry is expected to grow in the upcoming years due to the higher demand for convenience products. The roasty, nutty, and earthy smell is reminiscent of coffee and cocoa, depending on substitution and concentration of pyrazines. The growing awareness of people about the ingredients and the origin of their daily food has strongly influenced the market with labels like “organic” and “natural.” Many flavor ingredients prepared by biotechnological methods have conquered the market recently and are destined to replace the ineffective (0.01% pyrazine kg−1 biomass) extraction from plants or animal sources. This review focuses on the achievements and challenges in pyrazine synthesis. The major part deals with an overview of methods such as the extraction of natural products, the chemical and biocatalytic synthesis, and fermentation by microorganisms. The different types of production are decisive for the declaration and value of the final product and span from 200–3500 US$ kg−1 for the synthetically produced or the naturally extracted 2,5‐dimethylpyrazine, respectively.

Metal‐Free Oxidative [5+1] Cyclization of 1,5‐Enynes for the Synthesis of Pyrazine 1‐Oxide

AbstractA chemo‐selective nitrosylation of 1,5‐enynes via a sequence of NO radical incorporation and intramolecular radical cyclization was reported. The formation of two C−N bonds and one C−O bond make this [5+1] cycloaddition reaction an efficient approach to synthesize pyrazine 1‐oxides in moderate to good yields. Metal‐free, short reaction time and mild conditions render this strategy more practical, eco‐friendly and convenient. Synthetic utility of this protocol is highlighted by scaffolds diversification.magnified image

Synthesis and Evaluation of Aldehyde Derivatives of Sulfonyl Chloride Quinoxaline

In pyrazine mesomeric interaction between the protonated & neutral nitrogen atoms probably destabilizes the cation.N, N’-diprotonation is very easier for pyrazine Synthesis of 2, 3-diphenylquinoxaline by phenylene-diamine in 16 ml of rectified spirit was added & combine solution was warm in water bath for 30 min. added water until slight colorless persist & allow to cool recrystallize the product in ethanol. Synthesis of 2, 3-diphenylquinoxaline 7-sulfonylchloride (R) using chlorosulfonic acid under ice-cold condition, then Synthesis of 2-hydroxyphenyl-2,3-diphenylquinoxaline-7-sulphonate(R1) throughresorcinol with 3ml pyridine & sulphonyl chloride derivative, Synthesis of 2-formylphenyl-2,3-diphenylquinoxaline-7-sulphonate(R7)obtained by reaction of salicylaldehyde with pyridine & sulphonyl chloride derivative then Synthesis of 3-formylphenyl-2,3-diphenylquinoxaline-7-sulphonate(R9) obtained by heating on water bath mixture of3-hydroxybenzaldehyde with pyridine & sulphonyl chloride, Synthesized quinoxaline derivatives were subjected to antimicrobial susceptibility testing by well diffusion method against gram positive (S.aureus, 2079) and gram negative bacteria (E. coli, 2685). The results of quinoxaline derivatives in terms of zone of inhibition recorded. MIC of quinoxaline derivative was determined by tube micro dilution technique against S. aureus and E. coli. The turbidity was measured by UV at about 420 nm. Hydrogen peroxide scavenging activity and 1, 1 diphenyl 2, picryl hydrazyl Method (DPPH) calculated and Most of the derivatives have shown comparable antioxidant activity in relation to standard Ascorbic acid and DPPH. Keywords: QSAR, Sulfonyl Chloride Quinoxaline, Ant-microbial, Antioxidant

Electrochemical oxidation synergizing with Brønsted-acid catalysis leads to [4 + 2] annulation for the synthesis of pyrazines

Electrochemical oxidative [4 + 2] annulation for the synthesis of pyrazines.

Chemo‐Enzymatic Synthesis of Pyrazines and Pyrroles

AbstractHerein we report the biocatalytic synthesis of substituted pyrazines and pyrroles using a transaminase (ATA) to mediate the key amination step of the ketone precursors. Treatment of α‐diketones with ATA‐113 in the presence of a suitable amine donor yielded the corresponding α‐amino ketones which underwent oxidative dimerization to the pyrazines. Selective amination of α‐diketones in the presence of β‐keto esters afforded substituted pyrroles in a biocatalytic equivalent of the classical Knorr pyrrole synthesis. Finally we have shown that pyrroles can be prepared by internal amine transfer catalyzed by a transaminase in which no external amine donor is required.

Chemo-Enzymatic Synthesis of Pyrazines and Pyrroles.

Herein we report the biocatalytic synthesis of substituted pyrazines and pyrroles using a transaminase (ATA) to mediate the key amination step of the ketone precursors. Treatment of α‐diketones with ATA‐113 in the presence of a suitable amine donor yielded the corresponding α‐amino ketones which underwent oxidative dimerization to the pyrazines. Selective amination of α‐diketones in the presence of β‐keto esters afforded substituted pyrroles in a biocatalytic equivalent of the classical Knorr pyrrole synthesis. Finally we have shown that pyrroles can be prepared by internal amine transfer catalyzed by a transaminase in which no external amine donor is required.

Ru-Catalyzed Synthesis of Pyrazines and Pyrroles from Ammonia and Diols

Key words pyrazines - pyrroles - dehydrogenation - ruthenium catalysis

Synthesis of Pyrazines Using Sugar Derived from Tobacco Cellulose and Hydrolyzed Tobacco F1 Protein as an Amino Acid Source

Summary An array of pyrazines have been synthesized using sugars derived from tobacco cellulose (CDS), ammonium hydroxide, and hydrolyzed tobacco F1 protein as a source of free amino acids (isolated amino acids from F1 hydrolysate, from filtered F1 hydrolysate and from non-filtered F1 hydrolysate). All reactions were performed at 120 °C for 60 min using a 40-mL Parr reaction vessel. Results showed that the addition of hydrolyzed F1 protein as free amino acid source increased the number of pyrazines with branched alkyl chains (for example, 2-butyl-3-methyl pyrazine) compared to when no amino acids were added. However, using isolated amino acids from hydrolyzed F1 protein versus just hydrolyzed F1 protein (filtered or not filtered) did not make a difference in yield or type of branched pyrazines. When non-filtered hydrolyzed F1 protein was used, the solution was much more viscous and contained suspended solid material when compared to the use of filtered hydrolyzed F1 protein. Addition of threonine (THR) to the reaction mixture did not increase the yield of pyrazines but did slightly shift the distribution of pyrazines toward those with three and four carbons attached. Similar but not identical arrays of pyrazines were obtained when somewhat resembling reaction conditions were applied on a larger reaction scale (~1.5 L). A significant 50%-decrease in pyrazine yield was observed when the reaction temperature was reduced from 120 to 100 °C. No noticeable difference in the array of pyrazines from these two reactions was observed. In the majority of cases, the presence of free amino acids resulted in an increase in pyrazine yield coupled with a change in the qualitative array of pyrazines. These results clearly illustrate that sugar prepared from tobacco cellulose (glucose) can be used just like high fructose corn syrup to prepare flavor compounds via Amadori and Maillard reactions. The evidence highlights that hydrolyzed amino acids from F1 tobacco protein can be used via Maillard reactions to produce complementary arrays of pyrazine flavor compounds.

Synthesis of Pyrazines and Quinoxalines via Acceptorless Dehydrogenative Coupling Routes Catalyzed by Manganese Pincer Complexes.

Base-metal catalyzed dehydrogenative self-coupling of 2-amino alcohols to selectively form functionalized 2,5-substituted pyrazine derivatives is presented. Also, 2-substituted quinoxaline derivatives are synthesized by dehydrogenative coupling of 1,2-diaminobenzene and 1,2-diols. In both cases, water and hydrogen gas are formed as the sole byproducts. The reactions are catalyzed by acridine-based pincer complexes of earth-abundant manganese.

Synthesis of a polymer-capped palladium nanoparticles and its application as a reusable catalyst in oxidative coupling reaction of α-hydroxyketones and 1,2-diamines for preparation of pyrazines and quinoxalines

A novel method for the synthesis of pyrazines and quinoxalines has been developed using α-hydroxyketones and 1,2-diamines in the presence of cross-linked poly(4-vinylpyridine)-stabilized Pd(0) nanoparticles, [P4-VP]-PdNPs. The catalyst was easily prepared and characterized using various techniques such as FT-IR and UV–Vis spectroscopy, AAS, TEM, FESEM, EDX analysis and XRD. The results confirm a good dispersion of palladium nanoparticles on the polymer support. The catalyst displayed good catalytic activity when applied to the synthesis of quinoxalines via condensation of α-hydroxyketones with 1,2-diamines. A few pyrazine derivatives and various quinoxalines are prepared via coupling reaction of α-hydroxyketones and 1,2-diamines in high–excellent yields (81–99%) with short reaction times. The quinoxalines products were characterized by FT-IR, 1H and 13C NMR spectroscopy, and the physical properties were compared to the literature values of known compounds. The advantages of the present method over conventional classical methods are rapid and very simple work-up, and the catalyst is reusable many times without a significant loss in its activity.

Review on the Synthesis of Pyrazine and Its Derivatives

Pyrazine is a kind of natural product which can be found in plants, animals, insects, marine organisms andmicroorganisms. The main function of pyrazine in living organisms is used as flavor of the raw foods. Pyrazine and its derivatives were also produced in industries mainly for fragrance, flavor and pharmaceutical applications. This review describes the historical development of pyrazine including the discovery and synthesis, to the recent synthetic approach of pyrazinium. In general, six synthetic approaches namely condensation reaction, ring closure, metal catalysis, green reaction, Maillard reaction and acid catalyst on N-substitution have been reviewed in this paper. The first five approaches are mainly aimed for the substitution at 2, 3, 5 and 6 positions in pyrazine ring, whereas the last approach is specifically for 1 and 4 positions in pyrazine. Keywords: Diazine, pyrazine, and Maillard reaction

Synthesis of Pyrazine–Thiazole Biheteroaryl Compounds through Base‐Promoted Oxidative Cross‐Dehydrogenative Coupling Reactions

AbstractAn efficient and concise one‐pot protocol for the oxidative cross‐dehydrogenative coupling reaction of pyrazine N‐oxides and 1,3‐azole derivatives has been developed. Commercially available and inexpensive 1,3‐azoles were used as the coupling partners. Various biheteroaryl compounds were obtained in up to 67 % yields. This methodology provides a convinent way to construct the pyrazine–thiazole biheteroaryl moieties. Thermogravimetric analysis indicated that the fracture temperature of one of the biheteroaryl compounds was about 237 °C.