The Bucherer-Bergs Multicomponent Synthesis of Hydantoins-Excellence in Simplicity

Hydantoins and their hybrids with other molecules represent a very important group of heterocycles because they exhibit diverse biological and pharmacological activities in medicinal and agrochemical applications. They also serve as key precursors in the chemical or enzymatic synthesis of significant nonnatural α-amino acids and their conjugates with medical potential. This review provides a comprehensive treatment of the synthesis of hydantoins via the Bucherer-Bergs reaction including the Hoyer modification but limited to free carbonyl compounds or carbonyl compounds protected as acetals (ketals) and cyanohydrins used as starting reaction components. In this respect, the Bucherer-Bergs reaction provides an efficient and simple method in the synthesis of important natural products as well as for the preparation of new organic compounds applicable as potential therapeutics. The scope and limitations, as well as a comparison with some other methods for preparing hydantoins, are also discussed.

One-Step Encapsulation of ortho-Disulfides in Functionalized Zinc MOF. Enabling Metal-Organic Frameworks in Agriculture

Application of natural products as new green agrochemicals with low average lifetime, low concentration doses, and safety is both complex and expensive due to chemical modification required to obtain desirable physicochemical properties. Transport, aqueous solubility, and bioavailability are some of the properties that have been improved using functionalized metal-organic frameworks based on zinc for the encapsulation of bioherbicides (ortho-disulfides). An in situ method has been applied to achieve encapsulation, which, in turn, led to an improvement in water solubility by more than 8 times after 2-hydroxypropyl-β-cyclodextrin HP-β-CD surface functionalization. High-resolution high-angle annular dark-field scanning transmission electron microscopy (HR HAADF-STEM) and integrated differential phase contrast (iDPC) imaging techniques were employed to verify the success of the encapsulation procedure and crystallinity of the sample. Inhibition studies on principal weeds that infect rice, corn, and potato crops gave results that exceed those obtained with the commercial herbicide Logran. This finding, along with a short synthesis period, i.e., 2 h at 25 °C, make the product an example of a new generation of natural-product-based herbicides with direct applications in agriculture.

Discovery of N-Aryl-pyridine-4-ones as Novel Potential Agrochemical Fungicides and Bactericides

A series of N-aryl-pyridine-4-one derivatives were designed and synthesized using maltol and antidesmone as lead compounds, and then their fungicidal/bactericidal activities and possible mechanism of action against Colletotrichum musae were explored. Most of these compounds exhibited significant fungicidal activity in vitro. Especially, compound 23 has more than 90% inhibitory activity against nine plant pathogenic fungi at 50 μg mL^-1, which is superior to azoxystrobin. Moreover, an in vivo bioassay also demonstrated that compound 23 exhibited high-efficiency broad-spectrum antifungal activity and can effectively control postharvest diseases of mango. In addition, it was found that compounds 22 and 23 can also effectively control rice bacterial leaf blight in pot experiments, which was even more effective than zhongshengmycin. Preliminary mechanism studies revealed that compound 23 may cause cell membrane and mitochondria destruction. These findings indicate that compound 23 can be used to develop potential agrochemical fungicides and bactericides.

Palladium-Catalyzed Cross-Coupling Reactions: A Powerful Tool for the Synthesis of Agrochemicals

Pd-catalyzed cross-coupling reactions have become essential tools for the construction of carbon-carbon and carbon-heteroatom bonds. Over the last three decades, great efforts have been made with cross-coupling chemistry in the discovery, development, and commercialization of innovative new pharmaceuticals and agrochemicals (mainly herbicides, fungicides, and insecticides). In view of the growing interest in both modern crop protection and cross-coupling chemistry, this review gives a comprehensive overview of the successful applications of various Pd-catalyzed cross-coupling methodologies, which have been implemented as key steps in the synthesis of agrochemicals (on R&D and pilot-plant scales) such as the Heck, Suzuki, Sonogashira, Stille, and Negishi reactions, as well as decarboxylative, carbonylative, α-arylative, and carbon-nitrogen bond bond-forming cross-coupling reactions. Some perspectives and challenges for these catalytic coupling processes in the discovery of agrochemicals are briefly discussed in the final section. The examples chosen demonstrate that cross-coupling chemistry approaches open-up new, low-cost, and more efficient industrial routes to existing agrochemicals, and such methods also have the capability to lead the new generation of pesticides with novel modes of action for sustainable crop protection.

Tailoring of a Potential Nanoformulated Form of Gibberellic Acid: Synthesis, Characterization, and Field Applications on Vegetation and Flowering

Nanoformulation of agrochemicals has become a potential choice to improve the physicochemical properties, enhance the utilization efficiency, and reduce the side effects and ecotoxicity of many hazardous chemicals. Here, we tailored a new formulation platform for gibberellic acid (GA) using the layered double hydroxides (LDH) as a potential carrier. Typically, we synthesized, characterized, and potentially applied the newly nanoformulated form of GA on the quantity and quality properties of Dendranthema grandiflorum cultivar. We also evaluated the synergetic effect of the carrier LDH on the release behavior of GA, showing a remarkable impact on the utilization efficiency of GA. The nanohybrid structure of GA also showed an enhanced thermal stability and safe preservation for the incorporated moieties. Taking into account the hazardous effect of free GA on the environment and human health, the hybrid technique of GA is one of the best choices among all of the studied protocols.

Rhamnolipids as platform molecules for production of potential anti-zoospore agrochemicals

Rhamnolipid biosurfactants have potential applications in the control of zoosporic plant pathogens. However, rhamnolipids have not been closely investigated for the anti-zoospore mechanism or for developing new anti-zoospore chemicals. In this study, RhL-1 and RhL-3 groups of rhamnolipids were used to generate the corresponding RhL-2 and RhL-4 groups and the free diacids. Conversion of RhL-3 to RhL-1 was also accomplished in vitro with cellobiase as the catalyst. The anti-zoospore effects of RhL-1-RhL-4 and the diacids were investigated with zoospores of Phytophthora sojae. For RhL-1-RhL-4, approximately 20, 30, 40, and 40 mg/L, respectively, were found to be the lowest concentrations required to stop movement of all zoospores, which indicates that the anti-zoospore effect remains strong even after RhL-1 and RhL-3 are hydrolyzed into RhL-2 and RhL-4. The free diacids required a significantly higher critical concentration of about 125 mg/L. Rhamnose can be obtained as a co-product.

Synthesis and antiviral bioactivity of novel 3-((2-((1E,4E)-3-oxo-5-arylpenta-1,4-dien-1-yl)phenoxy)methyl)-4(3H)-quinazolinone derivatives

A series of novel 3-((2-((1E,4E)-3-oxo-5-arylpenta-1,4-dien-1-yl)phenoxy)methyl)-4(3H)-quinazolinone derivatives were designed and synthesized. Antiviral bioassays indicated that a few of the compounds exhibited higher antiviral activities against tobacco mosaic virus (TMV) in vivo than the commercial agent ningnanmycin. In particular, compounds A5, A12, A25, and A27 possessed appreciable curative bioactivities on TMV in vivo, with 50% effective concentration values ranging from 132.25 to 156.10 μg/mL. These values are superior to that of ningnanmycin (281.22 μg/mL) and suggest that novel 4(3H)-quinazolinone derivatives containing 1,4-pentadien-3-one moiety can effectively control TMV. Evaluation of the antiviral properties in field studies and the mechanisms underlying the enhanced antiviral activities of these derivatives are an interesting topic for future investigation.

Synthesis of Naturally Derived Bioactive Compounds of Agricultural Interest

Synthetic studies on bioactive compounds are described, involving phytotoxins (tobacco wildfire disease toxin tabtoxinine-beta-lactam and rice blast disease toxin pyricuol) a glutarimide antibiotic (actiketal) black vomit toxin (gizzerosine) and marine products (antifeedant pteroenone and serinol compound didemniserinolipid).

Design, synthesis, and structure-activity relationship of novel aniline derivatives of chlorothalonil

Chlorothalonil with both low cost and low toxicity is a popularly used fungicide in the agrochemical field. The presence of nucleophilic groups on this compound allows further chemical modifications to obtain novel chlorothalonil derivatives. Fluazinam, another commercially available agent with a broad fungicidal spectrum, has a scaffold of diaryl amine structure. To mimic this backbone structure, a variety of (un)substituted phenyl amines was used as nucleophilic agents to react with chlorothalonil to obtain compounds with a diphenyl amine structure. Via an elegant design, two leads, 2,4,5-trichloro-6-(2,4-dichlorophenylamino)isophthalonitrile (7) and 2,4,5-trichloro-6-(2,4,6-trichlorophenylamino)isophthalonitrile (11), with potential fungicidal activity were discovered after a preliminary bioassay screen. These two leads were further modified to obtain final products by replacing the chlorine groups in the phenyl ring in phenyl amine with other functional groups. These functional groups with various electronic properties and spatial characteristics were considered to explore the relationship between structure and fungicidal activity. The results indicate that the electron-withdrawing group NO2 on the 4 position on the right phenyl ring plays a unique role on enhancing the fungicidal activity. The compounds were identified by proton nuclear magnetic resonance and elemental analysis. Bioassays demonstrated that some of the title compounds exhibited excellent fungicidal activities against cucumber downy mildew at 25 mg/L. Compound 20 has been shown as the optimal structure with 85% control against cucumber downy mildew at 6.25 mg/L concentration. The relationship between structure and fungicidal activity is reported. The present work demonstrates that chlorothalonil derivatives can be used as possible lead compounds for developing novel fungicides.

Heterocyclic chemistry in crop protection

An overview is given of the significance of heterocycles in crop protection chemistry, which is enormous as more than two-thirds of all agrochemicals launched to the market within the last 20 years belong to this huge group of chemicals. This review focuses on two important aspects of heterocyclic agrochemistry: the different roles of heterocyclic scaffolds in crop protection agents and the major possibilities for their synthesis.

Utilization of wheat straw for the preparation of coated controlled-release fertilizer with the function of water retention

With the aim of improving fertilizer use efficiency and minimizing the negative impact on the environment, a new coated controlled-release fertilizer with the function of water retention was prepared. A novel low water solubility macromolecular fertilizer, poly(dimethylourea phosphate) (PDUP), was "designed" and formulated from N,N'-dimethylolurea (DMU) and potassium dihydrogen phosphate. Simultaneously, an eco-friendly superabsorbent composite based on wheat straw (WS), acrylic acid (AA), 2-acryloylamino-2-methyl-1-propanesulfonic acid (AMPS), and N-hydroxymethyl acrylamide (NHMAAm) was synthesized and used as the coating to control the release of nutrient. The nitrogen release profile and water retention capacity of the product were also investigated. The degradation of the coating material in soil solution was studied. Meanwhile, the impact of the content of N-hydroxymethyl acrylamide on the degradation extent was examined. The experimental data showed that the product with good water retention and controlled-release capacities, being economical and eco-friendly, could be promising for applications in agriculture and horticulture.

Overview on the history of organofluorine chemistry from the viewpoint of material industry

Fluorine (from "le fluor", meaning "to flow") is a second row element of Group 17 in the periodic table. When bound to carbon it forms the strongest bond in organic chemistry to give organofluorine compounds. The scientific field treating them, organofluorine chemistry, started before elemental fluorine itself was isolated. Applying the fruits in academia, industrial organofluorine chemistry has developed over 80 years via dramatic changes during World War II. Nowadays, it provides various materials essential for our society. Recently, it utilizes elemental fluorine itself as a reagent for the introduction of fluorine atoms to organic molecules in leading-edge industries. This paper overviews the historical development of organofluorine chemistry especially from the viewpoint of material industry.

Enantioselective synthesis of a simple benzenoid analogue of glycinoeclepin A

A synthesis of the readily accessible glycinoeclepin A analogue 2 is reported.

Synthesis and antifungal activity of a series of N-substituted [2-(2,4-dichlorophenyl)-3-(1,2,4-triazol-1-yl)]propylamines

A series of N-mono- or N, N-disubstituted [2-(2,4-dichlorophenyl-3-(1,2,4-triazol-1-yl)]propylamines and N-[2-(2,4-dichlorophenyl-3-(1,2,4-triazol-1-yl)propyl]amides were synthesized and tested for their fungicidal activity in vitro and in vivo against a group of plant pathogenic fungi. Some compounds exhibited a fairly good in vitro activity. The replacement of the ether group of tetraconazole with a secondary or tertiary amino group leads to compounds that maintain the antifungal activity on several phytopathogenic fungi, provided that the substituents are not too bulky or lipophilic. The allyl, propargyl, and cyclopropyl groups appear particularly suitable. Although these compounds have some structural similarities with terbinafine and naftifine, which act as squalene epoxidase inhibitors, they maintain the usual mechanism of action of the other triazoles.

Preparation of aromatic β-Selenolactams and their bioactivities as agricultural chemicals

The purpose of this study was to investigate the possibility of aromatic beta-selenolactams being used in agricultural chemicals. A series of beta-selenolactams with aromatic substituents at the 1-, 2- and 3-positions were synthesized and their bioactivities were evaluated. Acarianicidal and insecticidal activity against common destructive insects, antibacterial activity against seven common plant pathogens, and plant growth activity of typical food crops were investigated. We found that introduction of 4-chloro and 4-methyl groups on 2- or 3-phenyl groups of the beta-selenolactam ring brought about acarianicidal activity against adults and eggs of Plutella xylostella. However, except for moderate to weak effect on fatality of Culex pipiens molestus Forskal, insecticidal activity against two other kinds of insects, antibacterial activity against plant pathogens, and activity on plant growth regulation were not detected among the beta-selenolactam derivatives.

Review of strobilurin fungicide chemicals

Strobilurins are natural products isolated and identified from specific fungi. Natural strobilurins were named in the order of their discovery as strobilurin-A followed by strobilurin-B, C, D etc. Their discovery opened the door for new chemistry of synthetic fungicides. Applying Quantitative Structural Activity Relationship (QSAR) on the structures of the natural strobilurins, many pesticide companies were able to discover many synthetic analogues that are more efficacious and more stable fungicides. At present there are about eight synthetic strobilurins in the fungicides worldwide market. Some of these products are worldwide registered for use as agrochemical and some are in the process of registration. This class of fungicides is relatively new, as crop protection products and information about them is still fairly scarce. In this review, syntheses and chemistry of natural and synthetic strobilurins are discussed. Also, the mode of action, efficacy, biotic/abiotic degradation, analytical methods, and agricultural uses are discussed.

Design, synthesis, and fungicidal activities of new strobilurin derivatives

Strobilurins are one of the most important classes of agricultural fungicides. To discover new strobilurin analogues with high activity against resistant pathogens, a series of new strobilurin derivatives bearing structurally diverse heterocycle side chains 3a-m and 4a-g were designed and synthesized via a microwave-assisted procedure. The advantages, such as good to excellent yields, shorter reaction times, mild reaction conditions, and simple purification procedures, distinguish the present synthetic protocol as a highly efficient method for the preparation of strobilurin thioether derivatives. Bioassays indicated that most of the compounds showed broad-spectrum fungicidal activity in vitro. Interestingly, as compared to the control of a commercial strobilurin fungicide, Kresoxim-methyl, compounds 3b, 3g, 4c, and 4d possessed remarkably higher in vitro fungicidal activity against six kinds of tested fungi. Exhilaratingly, compound 3g exhibited higher in vivo activity against Sphaerotheca fuliginea and Pseudoperoniospora cubensis than Kresoxim-methyl, and the in vivo fungicidal activities of compound 4d and Kresoxim-methyl against S. fuliginea and P. cubensis are at the same level. The present work demonstrated that strobilurin analogues containing benzothiazole side chains could be used as a lead structure for further developing novel fungicides.

In situ monitoring of clastogenicity of ambient air in Bratislava, Slovakia using the Tradescantia micronucleus assay and pollen abortion assays

Aim of this study was to monitor the genotoxic effects of polluted air in Bratislava (Slovakia) with the Tradescantia micronucleus (Trad-MN) test. In situ monitoring was carried out at five locations during two seasons (years 2003 and 2004). Flower pots with Tradescantia paludosa (clone 03) plants were exposed for 6-8 weeks at the different sites each year. The highest MN levels were observed in the vicinity of an agrochemical factory (3.1 times higher than background level in 2003 and 2.7 times higher in 2004). Lower effects were seen when plants were exposed to urban traffic emissions or in the vicinity of a glass-producing plant (the MN frequencies ranged between 2.8 and 4.4 per 100 tetrads, respectively, while the control frequencies were 2.1-2.6 per 100 tetrads); exposure near a petrochemical plant had no significant effects. In pollen abortion assays, three wild growing species were used, namely, chicory (Cichorium intybus L.), old man's beard (Clematis vitalba L.) and common toadflax (Linaria vulgaris Mill.). Again, the strongest effects were observed close to the agrochemical industry (reduction of fertile pollen by 5.6%, 11.1% and 8.3% in chicory, old mans beard and in toadflax, respectively). Cichorium intybus was the most sensitive species and the number of abortive pollen grains was 5.1 times higher in specimens collected near the agrochemical factory than that seen at the control location. These observations indicate that contaminated urban air has an impact on the fertility of wild plants. Furthermore, it is interesting that the same rank order of effects was seen in pollen abortion assays as in the Trad-MN test (agrochemical industry>technical glass industry≥traffic>city incinerator/petrochemical plant). These results confirm the sensitivity of the Tradescantia MN test and pollen abortion assays for the detection of air pollution, and show that distinct differences exist in genotoxicity of different sources of pollutants.

Applications of combinatorial chemistry in the agrosciences

During the past ten years combinatorial chemistry developed from a powerful synthetic methodology, providing large libraries of usually simple new chemical entities, to a comprehensive strategy presently covering a multitude of technologies across the whole workflow from hit generation to lead optimization. Thus combinatorial chemistry had a major impact not only on the pharmaceutical research but also with some delay on the agrochemical research. The agrochemical discovery environment is different from that of the pharmaceutical research in that it relies mainly on whole organism screenings. This review summarizes some recent applications of combinatorial chemistry in the agrosciences, covering all the three major fields of research: fungicides, herbicides, and insecticides. The article focuses on libraries with published biological activities and thus highlights some characteristic features of successful agrochemical libraries, which may be fundamentally different from pharmaceutical libraries.

Targeting Chemical Inputs and Optimising HTS for Agrochemical Discovery

In vivo high throughput screening (HTS) has been adopted by most of the larger crop protection companies as an important tool for the discovery of new agrochemicals. There has been a paradigm shift in capabilities from screening a few thousand compounds a year to several hundred thousand and the quantity of screening sample required has fallen dramatically. The unifying goal now bringing together screens and inputs is the need to maximise the flow of useful information from HTS and thereby minimise the time taken to discover robust leads and new products. This review examines the positive changes that have occurred towards targeted design and selection of chemical inputs for agrochemical discovery over the last ten years and corresponding developments in HTS assays, data analysis and the logistics of compound storage and dispensing.

Synthesis and agrochemical screening of a library of natural product-like bicyclo[2,2,2]octenones

A general route to a series of differentially substituted bicyclo[2,2,2]octenones has been developed, making use of the in situ intramolecular Diels Alder reaction of masked ortho-benzoquinones. This approach was used to synthesize a series of thirteen key acid-containing templates from which a solution phase discovery library of 1126 diverse amides was then constructed. The rigid polycyclic nature of the templates and the prevalence of oxygenated functionality confer natural product-like qualities and three-dimensional diversity. The library was screened in HTS in vivo against a number of weed, insect and fungal model organisms leading to the discovery of a novel series of herbicidally active compounds. The development, production and biological activity of the library are described.

The Design and Synthesis of a Herbicide Targeted Library of N-[1-(1,3- Benzoxazol-2-yl)Alkyl]-6-Alkyl-1,3,5-Triazine-2,4-Diamines

Amino acids were immobilised by attaching them via a carbamate linker to Wang resin. These intermediates were converted to 1-(1,3-benzoxazol-2-yl)alkanamines over three steps, followed by coupling with 4-alkyl-6-chloro-1,3,5-triazine-2-amines to furnish the desired N-[1-(1,3-benzoxazol-2-yl)alkyl]-6-alkyl-1,3,5-triazine-2,4-diamines. Physico-chemical property profiles were used to support design and development of a combinatorial library. The synthetic methodology described herein was validated with the production of a herbicide targeted library of 300 members.

Automated Synthesis & Purification at Bayer CropScience Chemistry Frankfurt

The Automated Synthesis and Purification team at Bayer CropScience in Frankfurt provides services and support in the areas of synthesis and post synthesis activities for chemists. This article describes our workflow and the special robotic systems used. We produce small to medium sized compound libraries using liquid phase techniques. An example of a compound library taken from the herbicide area is given.

Solid Supported Synthesis of Phosphinates Via Palladium (0) Catalysed Coupling Reactions

In order to gain a broad access to phosphinic acid derivatives, a palladium catalysed coupling reaction of aryl iodides with hypophosphorous acid derivatives has been developed on the solid phase. The resulting arylphosphorous acids (or esters) were derivatised using addition reactions with aldehydes, imines and isocyanates, to give phosphinic acids (or esters) with alpha-hydroxy, alpha-amino or aminoacyl groups attached to the aryl phosphorus moiety. This approach provided a broad chemical entry into a class of polar phosphinates compounds which were rather difficult to handle using normal solution phase synthesis. The synthetic potential of this solid phase based methodology was demonstrated by the synthesis of targeted libraries against the enzyme dihydrodipicolinate synthase (DHDPS).

Parallel, Solution Phase Synthesis of Dihydropyridine Miticides Via a Versatile Multicomponent Reaction

A novel class of highly active dihydropyridine miticides was prepared using a multicomponent reaction process. The initial lead was rapidly optimized using solution phase parallel synthesis techniques and a positional scanning approach. Detailed structure-activity relationships were developed for the amino and carbonyl components of the molecule and used to select the best candidates for broad field testing. The chemistry, biology and toxicology of these compounds will be presented along with numerous structural variants of the reaction products.

The Design, Synthesis and Screening of a Muscarinic Acetylcholine Receptor Targeted Compound Library

Potent new agonists of the insect muscarinic acetylcholine receptor (mAChR) have been discovered by synthesizing and screening a library of 225 oxime ether amines. Library evaluation was facilitated by the development of a high throughput test enabling the rapid determination of muscarinic agonist activity. The most interesting compounds were the thiadiazole 17 and the isoxazole 24 which were potent muscarinic agonists (EC50 13 and 21 nM, respectively) and showed lead levels of insecticidal activity.

Lipases for biotechnology

Lipases constitute the most important group of biocatalysts for biotechnological applications. The high-level production of microbial lipases requires not only the efficient overexpression of the corresponding genes but also a detailed understanding of the molecular mechanisms governing their folding and secretion. The optimisation of industrially relevant lipase properties can be achieved by directed evolution. Furthermore, novel biotechnological applications have been successfully established using lipases for the synthesis of biopolymers and biodiesel, the production of enantiopure pharmaceuticals, agrochemicals, and flavour compounds.

A review of the natural occurrence, synthetic production and use of carcinogenic hydrazines and related chemicals

This writing details the natural occurrence, synthetic production and use of the carcinogenic hydrazines and related chemicals. Twenty-three such chemicals were found in nature in mushrooms, tobacco, bay leaves, antibiotics, soil and other sources. The synthetically-produced hydrazines and related chemicals include 61 compounds which were or are in use as pharmaceutical drugs, agricultural substances, industrial chemicals and fuels for military and space vehicles and rockets. Because there is an overlap between the naturally-occurring and synthetically-produced compounds, their total number is 76. Altogether, 98 hydrazines and related chemicals were studied for carcinogenic action thus far, of which 84 were found to be carcinogenic and the remaining 14 were inactive. This means that the human population is exposed in various degrees to a substantial number of these agents. Therefore, the hydrazine class, unlike the polycyclic aromatic hydrocarbons, N-nitroso compounds, and aromatic amines, poses a greater environmental risk to the human population. In view of these considerations, it appears reasonable to proceed with additional experimentation in this field of interest.