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Prenylated polyphenols occur naturally and exhibit biological activity superior to the ubiquitous parent polyphenols. However, their low abundance limits the wider application of these derivatives. In this work, we present an expedient, single-step catalytic protocol for introducing terpene fragments into the aromatic rings of the widely available natural stilbenoids and flavonoids to upgrade their therapeutic potential. [ABSTRACT FROM AUTHOR]

Due to the diverse structures and broad functions of terpenes, microbial biosynthesis of these compounds has been favored as a sustainable alternative to phytoextraction and chemosynthesis. Here, systematic metabolic engineering strategies were explored in the oleaginous yeast Yarrowia lipolytica for hyperproducing sesquiterpene germacrene A which serves as an important intermediate of numerous anticarcinogens. By identifying the most efficient germacrene A synthase to date, reconstructing the endogenous mevalonate pathway and extending the cytosolic acetyl-CoA pool by regulating lipid metabolism, the resulting strain overproduced 2.794 g L−1 germacrene A in shake flasks, which represented a 38-fold improvement over the initial strain. The engineered strain was subsequently capable of producing 39 g L−1 germacrene A at a yield of 0.181 g g−1 glucose during optimized bioreactor fermentation, with this being the highest sesquiterpene production level reported to date for Y. lipolytica. These results demonstrate that reprogramming the metabolism of the host cell by systematic metabolic engineering plays an essential role in diverting its inherent metabolic fluxes for sesquiterpene biosynthesis and these approaches can be extensively applied for synthesizing natural terpenes. [ABSTRACT FROM AUTHOR]

The comprehensive utilization of agro-industrial residues poses a persistent global challenge. Microbial fermentation is an efficient way to convert agro-industrial residues into valuable products. Trichoderma reesei is a traditional cellulase and other protein producer using agro-industrial residues as substrates. The potential of T. reesei as a chassis to produce small natural products remains untapped. Here, we successfully employed T. reesei to efficiently synthesize different terpene types. To optimize the chassis for metabolite synthesis, we deleted major (hemi-)cellulase genes along with the global regulator Lae1 to improve the efficiency of secondary metabolite biosynthesis, and overexpressed the constitutively activated transcriptional factor XYR1A824V in MC3 (a uridine auxotrophic strain derived from T. reesei Rut-C30) to alleviate glucose repression. Through glucose, lactose, and corn steep as substrates, the production of ophiobolin F using the modified chassis was increased to 1187.06 mg L−1 in shake flask fermentation and up to 3072.45 mg L−1 under fed-batch fermentation. We further demonstrated the versatility of the Δlae1::xyr1/MC3-Δ10 chassis by successfully producing other fungal and plant terpenes. Collectively, our results demonstrated the potential of the Reducing Outflow and Broadened Upstream Substrate Type (ROBUST) T. reesei chassis for efficient terpene production utilizing agro-industrial residues, with important implications for terpene biosynthesis and sustainable biofabrication. [ABSTRACT FROM AUTHOR]

Fungal meroterpenoids are secondary metabolites from mixed terpene-biosynthetic origins. Their intriguing chemical structural diversification and complexity, potential bioactivities, and pharmacological significance make them attractive targets in natural product chemistry, organic synthesis, and biosynthesis. This review provides a systematic overview of the isolation, chemical structural features, biological activities, and fungal biodiversity of 1585 novel meroterpenoids from 79 genera terrestrial and marine-derived fungi including macrofungi, Basidiomycetes, in 441 research papers in 2009-2019. Based on the nonterpenoid starting moiety in their biosynthesis pathway, meroterpenoids were classified into four categories (polyketide-terpenoid, indole-, shikimate-, and miscellaneous-) with polyketide-terpenoids (mainly tetraketide-) and shikimate-terpenoids as the primary source. Basidiomycota produced 37.5% of meroterpenoids, mostly shikimate-terpenoids. The genera of Ganoderma, Penicillium, Aspergillus, and Stachybotrys are the four dominant producers. Moreover, about 56% of meroterpenoids display various pronounced bioactivities, including cytotoxicity, enzyme inhibition, antibacterial, anti-inflammatory, antiviral, antifungal activities. It's exciting that several meroterpenoids including antroquinonol and 4-acetyl antroquinonol B were developed into phase II clinically used drugs. We assume that the chemical diversity and therapeutic potential of these fungal meroterpenoids will provide biologists and medicinal chemists with a large promising sustainable treasure-trove for drug discovery.

Hydrophobic deep eutectic solvents were investigated for tetracycline microextraction. It was found that a deep eutectic solvent consisting of thymol and octanoic acid provided a synergistic effect on tetracycline extraction. In this paper, a novel liquid–liquid microextraction procedure for the HPLC-DAD determination of tetracyclines in milk samples was proposed. [ABSTRACT FROM AUTHOR]

Atrachinenynes A–D (1–4), four novel diacetylenic derivatives, were isolated for the first time from the rhizomes of Atractylodes chinensis. Compound 1 features a new C26 skeleton with an unusual 8/6/6/5 tetracyclic ring system bearing a diacetylene sidechain. Compounds 2–4 are three novel diacetylenic terpenoids with an additional six-membered ring between terpenes and diacetylenes formed via a Diels–Alder reaction. The structures and the absolute configurations of 1–4 were elucidated by spectroscopic methods, electronic circular dichroism (ECD) calculations, and 13C quantum chemical calculations. Their plausible biogenetic pathways were also proposed. [ABSTRACT FROM AUTHOR]

Covering: 2000 to 2023 This review presents the exceptional story of ophiobolin A (OphA) and sphaeropsidin A (SphA), a sesterterpene and a diterpene, respectively, which were initially isolated as fungal phytotoxins and subsequently shown to possess other interesting biological activities, including promising anticancer activities. Ophiobolin A is a phytotoxin produced by different fungal pathogens, all belonging to the Bipolaris genus. Initially, it was only known as a very dangerous phytotoxin produced by fungi attacking essential cereals, such as rice and barley. However, extensive and interesting studies were carried out to define its original carbon skeleton, which is characterized by a typical 5 : 8 : 5 ring system and shared with fusicoccins and cotylenins, and its phytotoxic activity on host and non-host plants. The biosynthesis of OphA was also defined by describing the different steps starting from mevalonate and through the rearrangement of the acyclic C-25 precursor lead the toxin is obtained. OphA was also produced as a bioherbicide from Drechslera gigantea and proposed for the biocontrol of the widespread and dangerous weed Digitaria sanguinaria. To date, more than sixty ophiobolins have been isolated from different fungi and their biological activities and structure–activity relationship investigated, which were also described using their hemisynthetic derivatives. In the last two decades, thorough studies have been performed on the potential anticancer activity of OphA and its original mode of action, attracting great interest from scientists. Sphaeropsidin A has a similar story. It was isolated as the main phytotoxin from Diplodia cupressi, the causal agent of Italian cypress canker disease, resulting in the loss of millions of plants in a few years in the Mediterranean basin. The damage to the forest, environment and ornamental heritage are noteworthy and economic losses are also suffered by tree nurseries and the wood industry. Six natural analogues of SphA were isolated and several interesting hemisynthetic derivatives were prepared to study its structure–activity relationship. Surprisingly, sphaeropsidin A showed other interesting biological activities, including antibiotic, antifungal, and antiviral. In the last decade, extensive studies have focused on the anticancer activity and original mode of action of SphA. Furthermore, specific hemisynthetic studies enable the preparation of derivatives of SphA, preserving its chromophore, which showed a noteworthy increase in anticancer activity. It has been demonstrated that ophiobolin A and sphaeropsidin A are promising natural products showing potent activity against some malignant cancers, such as brain glioblastoma and different melanomas. [ABSTRACT FROM AUTHOR]

Covering: up to July 2023 Terpene cyclases (TCs) catalyze some of the most complicated reactions in nature and are responsible for creating the skeletons of more than 95 000 terpenoid natural products. The canonical TCs are divided into two classes according to their structures, functions, and mechanisms. The class II TCs mediate acid–base-initiated cyclization reactions of isoprenoid diphosphates, terpenes without diphosphates (e.g., squalene or oxidosqualene), and prenyl moieties on meroterpenes. The past twenty years witnessed the emergence of many class II TCs, their reactions and their roles in biosynthesis. Class II TCs often act as one of the first steps in the biosynthesis of biologically active natural products including the gibberellin family of phytohormones and fungal meroterpenoids. Due to their mechanisms and biocatalytic potential, TCs elicit fervent attention in the biosynthetic and organic communities and provide great enthusiasm for enzyme engineering to construct novel and bioactive molecules. To engineer and expand the structural diversities of terpenoids, it is imperative to fully understand how these enzymes generate, precisely control, and quench the reactive carbocation intermediates. In this review, we summarize class II TCs from nature, including sesquiterpene, diterpene, triterpene, and meroterpenoid cyclases as well as noncanonical class II TCs and inspect their sequences, structures, mechanisms, and structure-guided engineering studies. [ABSTRACT FROM AUTHOR]

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as kadsuraol A from Kadsura longipedunculata. [ABSTRACT FROM AUTHOR]

A new photoelectron spectroscopic method permitting a quantitative analysis of the volatile headspace of several essential oils is presented and discussed. In particular, we focus on the monoterpene compounds, which are known to be the dominant volatile components in many such oils. The photoelectron spectra of the monoterpene constituents may be effectively isolated by accepting for analysis only those electrons that accompany the production of m/z = 136 ions, and by using low photon energies that restrict cation fragmentation. The monoterpene isomers are then identified and quantified by regression modelling using a library of terpene standard spectra. An advantage of this approach is that pre-concentration of the volatile vapour is not required, and all steps are performed at ambient temperature, avoiding the possible deleterious effects (such as isomerisation/decomposition) that may sometimes arise in gas chromatographic (GC) procedures. As a proof-of-principle demonstration, three citrus oils (lemon, lime, bergamot) are analysed with this approach and the results are compared with reported GC composition profiles obtained for these oils. Potential advantages of the methodology that include multiplex detection and real-time, in situ analysis are identified and discussed. Alternative and faster experimental implementations concerning laboratory-based ionization and detection schemes are proposed and considered, as is the possibility of a straightforward extension towards simultaneous determination of enantiomeric excesses. [ABSTRACT FROM AUTHOR]

Inspired by traditional solvents for carboxylic acid extraction being not environmentally friendly, novel hydrophobic deep eutectic solvents (DESs) based on amides as hydrogen bond acceptors (HBAs) and terpenes as hydrogen bond donors (HBDs) were proposed as sustainable solvents. The structures were characterized by 1H NMR and GC-MS, meanwhile the formation mechanism was revealed by electrostatic potential (ESP) analysis. In addition, the partition coefficients and separation factors of lactic, malic, and tartaric acids (LA, MA, and TA) in novel DESs were tested by a simple solvent extraction approach. What's more, the contributions of HBAs and HBDs in improving the selective separation of carboxylic acids were confirmed by multiscale exploration and experimental research. HBAs increase the partition coefficient via forming double hydrogen bonds with LA, MA, and TA. HBDs improve the selectivity by competition with these acids. This finding can serve as a blueprint for the design of greener solvents for the selective separation of carboxylic acids in bioprocesses. [ABSTRACT FROM AUTHOR]

Plant volatile terpenoids (PVTs) are the main aroma components of flowers, fruits, and vegetables. Citronellol, geraniol, and nerol are the three major components of rose oil, which has wide applications in aromatherapy, perfumes, and cosmetics. However, the current production of rose oil through the distillation of flowers is not sustainable and cannot meet the increasing market demand. Here, we firstly reconstructed the biosynthetic pathway of citronellol in the platform yeast strain HP001, which overexpresses the MVA-pathway genes, resulting in the production of 7.87 mg L−1 citronellol. To further increase the production, the native promoter of ERG20 was replaced by the promoter of ERG7, and the expression of the geraniol-synthesis module was enhanced. The resulting strain exhibited a remarkable 4450% increase of the citronellol titer, reaching 0.36 g L−1 in shake flasks and 6.37 g L−1 in a bioreactor. Furthermore, the entire synthetic pathways of these three rose oil monoterpenoids were reconstituted in yeast, resulting in Rose-yeast 1.0, with a titer of 124.0 mg L−1 in shake flasks and 4.87 g L−1 in a bioreactor. Rose-yeast 1.0 produced a synthetic rose oil comprising a correct ratio of citronellol (62.30%), geraniol (27.39%), and nerol (10.31%), closely matching that of Rosa × damascena MILLER. Additionally, the ERG7 promoter was inserted in front of the native ERG9 gene, and the metabolic flux of the sesquiterpenoid synthesis was assessed by introducing the biosynthetic pathways of nerolidol and valencene. The maximal titer of the resulting strain reached 912.72 mg L−1 nerolidol and 5.30 mg L−1 valencene in shake flasks. This synthetic biology platform for mono- and sesquiterpenoid production can serve as a basis for creating a sustainable microbial source of important PVTs. [ABSTRACT FROM AUTHOR]

The paper reviews the known examples of cyclic terpenoids produced from open chain polyenic precursors by an "unusual" biosynthetic pathway, involving selective electrophilic attack on an internal double bond followed by cyclization. The resulting compounds possess cyclic backbones with pendant terminal prenyl groups. Synthetic approaches applied for the synthesis of such specifically functionalized compounds are also discussed, as well as biological activity of reported representatives.

The potential of using turpentine for the production of biorenewable chemicals within a biorefinery context is discussed, focussing on the development of practical methodology to convert the bicyclic monoterpene components present in untreated crude sulfate turpentine into mixtures of synthetically useful p-menthadienes (p-MeDs) as feedstocks for chemical production. A simple and scalable biphasic acid catalysed ring-opening (ACRO) protocol employing recyclable 6 M aq. H2SO4 at 90 °C has been developed to transform the major bicyclic monoterpenes (β-pinene, α-pinene, and 3-carene) in untreated commercial crude sulfate turpentine (CST) into mixtures of monocyclic p-MeDs in >70% yield. Investigations using pure bicyclic monoterpenes reveal that the ∼3 mol% Me2S present in CST plays a key role in increasing the rate and yield of these ACRO reactions. Reaction monitoring studies have identified the presence of induction periods and autocatalytic effects, as well as an intriguing time-dependent increase in p-MeD yield after all the bicyclic terpene substrate has been consumed. These effects have been explained using a mechanism that invokes reversible addition of Me2S to the alkene bonds of monoterpenes to produce in situ generated sulfonium salts. These sulfonium salts then function as surfactants to increase the degree of mixing of the aqueous/terpene layers of the biphasic ACRO reaction, resulting in faster protonation of the alkene bonds of the bicyclic terpenes in the rate-determining step. The shorter reaction times of the Me2S facilitated ACRO reactions of CST and gum turpentine enable better yields of p-MeDs to be obtained by minimising p-MeD losses to competing polymerisation pathways that occur at elevated temperatures over time. [ABSTRACT FROM AUTHOR]

The impact values for the environmental emissions of 52 solvents are estimated and expressed in monetary units. The impact values of solvents present in the air are calculated on the basis of 13 impact indicators and additional 2 impact indicators for solvents present in water. These impact values are weighed with the results obtained with a multi-compartment distribution model, allowing the calculation of the fraction of solvent emitted to the environment present in each of the compartments. The results show that the impact values of solvent emissions are in the range of 0.7–1179.51 $ L−1, with a mean value of 20.69 $ L−1, expressed in USD2019. These impacts are considerably lower for short-chain aliphatic hydrocarbons, alcohols, ethers, aldehydes, ketones, and esters. High impact values are obtained for long-chain aliphatic hydrocarbons, aromatic hydrocarbons, terpenes, and an extremely high value for carbon tetrachloride. Monetary values calculated to assess the solvent emission impact have the advantage that they are quantitative and easily applicable. [ABSTRACT FROM AUTHOR]

The increasing regulations and restrictions in favour of a biobased and sustainable community could potentially harm the strong economic position of the polymer industry, which still heavily relyies on crude oil. The adhesive industry, in particular, is looking for more renewable alternatives and more environmentally friendly synthesis routes. In this work, (meth)acrylate derivatives of terpenoids, namely tetrahydrogeraniol, citronellol, menthol and isoborneol are introduced in the synthesis of waterborne pressure-sensitive adhesives (PSA) based on acrylic latexes via emulsion polymerisation. This industrially implemented setting enables the preparation of five different formulations with high biobased content with a renewable carbon content ranging from 70 to 100%. The biobased PSAs are found to be comparable in terms of tack, peel strength and shear resistance to a benchmark petroleum-derived commercial product. They show good adhesion properties on steel, glass and polyethylene surfaces. Moreover, the various formulations displayed different mechanical and adhesion properties, which make them attractive for a wide range of applications. [ABSTRACT FROM AUTHOR]

Mononuclear zinc(II) and cadmium(II) complexes, ZnLCl2 (1), CdLCl2 (2), ZnL1Cl2·2H2O (3), and CdL1Cl2·2H2O (4), with chiral ligands containing a 2,2′-bipyridine moiety and natural terpene (+)-limonene (L) or (+)-3-carene (L1) moieties were synthesized. In these complexes the L and L1 ligands are shown to coordinate Zn2+ and Cd2+ ions through the 2,2′-bipyridine moiety. The acetamide group of the ligands interacts with M2+ ions by forming N⋯M2+ and C＝O⋯M2+ contacts and N–H⋯Cl hydrogen bonds with coordinated Cl− ions. In solutions the complexes have several conformers differing by the degree of the turn of the acetamide moiety relative to the ligand core and the type of its interaction with the coordination core. The ligands and complexes exhibit luminescence with the quantum yield increasing in the order: ligand < cadmium(II) complex < zinc(II) complex. The complexes 3 and 4 demostrate excitation wavelength independent single-channel fluorescence. As opposed to 3 and 4, the complexes 1 and 2 demonstrate excitation wavelength dependent emission with nanosecond and microsecond lifetimes of the excited states. According to our TD-DFT calculations, an interplay of ligand centered and halide to ligand transitions facilitates two deactivation channels in 1 and 2: S1–S0 and T1–S0. [ABSTRACT FROM AUTHOR]

First reported in 2004, and subsequently advanced by Chemat's team and other research teams in the following two decades, the use of D -limonene as a natural product extraction solvent offers multiple benefits that go beyond its environmentally benign nature. Following a review of the main research achievements concerning the use of this biosolvent in the extraction of widely different natural products, we offer a comprehensive perspective including usually neglected economic and safety aspects. The study concludes by identifying three main research outcomes and providing two guidelines to bioeconomy practitioners willing to use this terpene in new natural production extraction and production processes. [ABSTRACT FROM AUTHOR]

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as macrophilone A from Macrorhynchia philippina. [ABSTRACT FROM AUTHOR]

Polyurethanes (PUs) are a versatile and major polymer family, mainly produced via polyaddition between polyols and polyisocyanates. A large variety of fossil-based building blocks is commonly used to develop a wide range of macromolecular architectures with specific properties. Due to environmental concerns, legislation, rarefaction of some petrol fractions and price fluctuation, sustainable feedstocks are attracting significant attention, e.g., plastic waste and biobased resources from biomass. Consequently, various sustainable building blocks are available to develop new renewable macromolecular architectures such as aromatics, linear aliphatics and cycloaliphatics. Meanwhile, the relationship between the chemical structures of these building blocks and properties of the final PUs can be determined. For instance, aromatic building blocks are remarkable to endow materials with rigidity, hydrophobicity, fire resistance, chemical and thermal stability, whereas acyclic aliphatics endow them with oxidation and UV light resistance, flexibility and transparency. Cycloaliphatics are very interesting as they combine most of the advantages of linear aliphatic and aromatic compounds. This original and unique review presents a comprehensive overview of the synthesis of sustainable cycloaliphatic PUs using various renewable products such as biobased terpenes, carbohydrates, fatty acids and cholesterol and/or plastic waste. Herein, we summarize the chemical modification of the main sustainable cycloaliphatic feedstocks, synthesis of PUs using these building blocks and their corresponding properties and subsequently present their major applications in hot-topic fields, including building, transportation, packaging and biomedicine. [ABSTRACT FROM AUTHOR]

The ability to be used as an alternative solvent of a cis-rich pinane (cis/trans: 7/3), which was obtained for the first time at the multigram scale through an environmentally friendly catalytic hydrogenation of α/β-pinenes or turpentine oil under neat conditions over a Pd/C catalyst, was investigated and compared to n-hexane for the extraction of several bioactive compounds. Experimental evaluation as well as a simulation of the cis-rich pinane extraction capacity have been undertaken. The predictive approach was performed using the simulation software COSMO-RS (conductor like screening model for realistic solvents), which uses a statistical thermodynamics approach based on the result of quantum chemical calculation, for the understanding of dissolving mechanism. COSMO-RS simulation showed that the bio-based solvent is a good solvent to solubilize carotenoids, oil from rapeseed and aromas from caraway seeds. The experimental results indicated that the highest carotenoid yield was obtained with the cis-rich pinane with 95.4% of the maximum carotenoid content in carrots while n-hexane was only able to extract 78.1% of them. With respect to the extraction of oil from rapeseeds, both solvents showed similar extraction yields and no differences were observed in the fatty acid profiles. In relation to the aromas, the characterization of the essential oil extracted by the two solvents showed a similar composition, where carvone (64%) was the main component followed by limonene (34%). No selectivity of the solvents was observed for any of the two major compounds. The results indicate that the bio-based solvent could be a promising solvent for n-hexane substitution. [ABSTRACT FROM AUTHOR]

A soil habitat consists of an enormous number of pigmented bacteria with the pigments mainly composed of diverse carotenoids. Most of the pigmented bacteria in the top layer of the soil are photoprotected from exposure to huge amounts of UVA radiation on a daily basis by these carotenoids. The photostability of these carotenoids depends heavily on the presence of specific features like a carbonyl group or an ionone ring system on its overall structure. Resonance Raman spectroscopy is one of the most sensitive and powerful techniques to detect and characterize these carotenoids and also monitor processes associated with them in their native system at a single cell resolution. However, most of the resonance Raman profiles of carotenoids have very minute differences, thereby making it extremely difficult to confirm if these differences are attributed to the presence of different carotenoids or if it is a consequence of their interaction with other cellular components. In this study, we devised a method to overcome this problem by monitoring also the photodegradation of the carotenoids in question by UVA radiation wherein a differential photodegradation response will confirm the presence of different carotenoids irrespective of the proximities in their resonance Raman profiles. Using this method, the detection and characterization of carotenoids in pure cultures of five species of pigmented coccoid soil bacteria is achieved. We also shed light on the influence of the structure of the carotenoid on its photodegradation which can be exploited for use in the characterization of carotenoids via resonance Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Covering: 1928–2021 Ginkgo biloba L. is one of the most distinctive plants to have emerged on earth and has no close living relatives. Owing to its phylogenetic divergence from other plants, G. biloba contains many compounds with unique structures that have served to broaden the chemical diversity of herbal medicine. Examples of such compounds include terpene trilactones (ginkgolides), acylated flavonol glycosides (ginkgoghrelins), biflavones (ginkgetin), ginkgotides and ginkgolic acids. The extract of G. biloba leaf is used to prevent and/or treat cardiovascular diseases, while many ginkgo-derived compounds are currently at various stages of preclinical and clinical trials worldwide. The global annual sales of G. biloba products are estimated to total US$10 billion. However, the content and purity of the active compounds isolated by traditional methods are usually low and subject to varying environmental factors, making it difficult to meet the huge demand of the international market. This highlights the need to develop new strategies for the preparation of these characteristic compounds from G. biloba. In this review, we provide a detailed description of the structures and bioactivities of these compounds and summarize the recent research on the development of strategies for the synthesis, biosynthesis, and biotechnological production of the characteristic terpenoids, flavonoids, and alkylphenols/alkylphenolic acids of G. biloba. Our aim is to provide an important point of reference for all scientists who research ginkgo-related compounds for medicinal or other purposes. [ABSTRACT FROM AUTHOR]

The etherification of β-citronellene with bioalcohols over zeolite beta was performed in a continuous flow liquid phase reactor. At 80 °C, the catalyst exhibits 50% β-citronellene conversion with a high selectivity for the etherification reaction. High chemoselectivity (90%) at the β-double bond of β-citronellene was observed, while β-citronellene isomers were formed as minor products. In order to rationalize the observed chemoselectivity, the relative stabilities of the protonated reaction intermediates were estimated using theoretical calculations. The zeolite beta catalyst exhibits high stability as well as low coke formation. Considering the industrial importance of terpene ethers as sophisticated solvents, fragrance or flavor additives, a novel and environmentally friendly synthesis is presented as an alternative to homogeneous catalysis using strong Brønsted or Lewis acids in solution. [ABSTRACT FROM AUTHOR]

New gelators, based on chiral triterpenoids linked with aromatic rings and amide structures, were designed and synthesized. Different chiral properties of assembly of the organogels were observed and these were expressed by different close degrees of molecular packing, which were attributed to the formation of H-type aggregates in the monotriterpenoid and of J-type aggregates in the bis-triterpenoid derivatives. The nanofibers of the organogel in dimethylsulfoxide were used to engineer gold nanoparticles and generate gel–nanoparticle hybrid materials. [ABSTRACT FROM AUTHOR]

Microwave assisted extraction has been demonstrated as an efficient green technology for the recovery of d-limonene from orange waste. Microwave irradiation was shown to be a more efficient method when compared to conventional heating due to its high selectivity for d-limonene, significantly shortened extraction durations and d-limonene yields twice that of conventional heating. Kinetic analysis of the extraction process indicated a typical two-step diffusion process, an initial stage of extraction from the exterior of the cells (1st stage) and diffusion of solute across the membrane (2nd stage). Diffusion coefficients for the initial stage of extraction from the exterior of cells (1st stage) for both conventional and microwave extraction demonstrated similar trends and activation energies. Interestingly, trans-membrane diffusion coefficient for the microwave assisted extraction at 110 °C was significantly high. Crucially, this was not observed with conventional heating suggesting that microwave radiation favourably interacts with the sample during extraction, causing simultaneous cell rupture and diffusion, resulting in greater yield. This provides an important insight into the development of extraction processes for orange peel. [ABSTRACT FROM AUTHOR]

Solvent-free continuous flow epoxidation of the alkene bonds of a range of biorenewable terpene substrates have been carried out using a recyclable tungsten-based polyoxometalate phase transfer catalyst and aqueous H2O2 as a benign oxidant. These sustainable flow epoxidation reactions are carried out in commercial microreactors containing static mixing channels that enable common monoterpenes (e.g. untreated crude sulfate turpentine, limonene, etc.) to be safely epoxidized in short reaction times and in good yields. These flow procedures are applicable for the flow epoxidation of trisubstituted and disubstituted alkenes for the safe production of multigram quantities of a wide range of epoxides. [ABSTRACT FROM AUTHOR]

Covering: up to mid-2019 This review highlights the utilization of biomass-derived building blocks in the total synthesis of natural products. An overview over several renewable feedstock classes, namely wood/lignin, cellulose, chitin and chitosan, fats and oils, as well as terpenes, is given, covering the time span from the initial beginning of natural product synthesis until today. The focus is put on the origin of the employed carbon atoms and on the nature of the complex structures that were assembled therefrom. The emerging trend of turning away from petrochemically derived starting materials back to bio-based resources, just as seen in the early days of total synthesis, shall be demonstrated. [ABSTRACT FROM AUTHOR]

Covering: up to 2015 This review summarises the accumulated knowledge about characterised bacterial terpene cyclases. The structures of identified products and of crystallised enzymes are included, and the obtained insights into enzyme mechanisms are discussed. After a summary of mono-, sesqui- and diterpene cyclases the special cases of the geosmin and 2-methylisoborneol synthases that are both particularly widespread in bacteria will be presented. A total number of 63 enzymes that have been characterised so far is presented, with 132 cited references. [ABSTRACT FROM AUTHOR]

Natural products produced by microorganisms and plants are a major resource of antibacterial and anticancer drugs as well as industrially useful compounds. However, the native producers often suffer from low productivity and titers. Here we summarize the recent applications of heterologous biosynthesis for the production of several important classes of natural products such as terpenoids, flavonoids, alkaloids, and polyketides. In addition, we will discuss the new tools and strategies at multi-scale levels including gene, pathway, genome and community levels for highly efficient heterologous biosynthesis of natural products. [ABSTRACT FROM AUTHOR]

Covering: 1963 up to the end of 2014 The biological activities of aristolane, aromadendrane, ent-1,10-secoaromadendrane, 2,3-secoaromadendrane, ent-5,10-cycloaromadendrane, bicyclogermacrene, lepidozane, and maaliane terpenoids which contain the gem-dimethylcyclopropyl unit are described. Particular attention is given to their anti-viral, anti-microbial and cytotoxic activities. In the main text there are 119 references covering the literature from 1963–2014. The ESI contains tables listing 332 of these terpenoids, their occurrence and biological activity together with the related references. [ABSTRACT FROM AUTHOR]

The complex [{(η5-Ind)Mo(CO)2(μ-Cl)}2] (1) has been tested for the industrially relevant catalytic isomerisation of α-pinene oxide (PinOx) to campholenic aldehyde (CPA) in the liquid phase. PinOx conversion and CPA selectivity are strongly influenced by the solvent employed. Complete conversion of PinOx was achieved within 1 min at 55 °C or 30 min at 35 °C using 1,2-dichloroethane as solvent, giving CPA in 68% yield. Other products included trans-carveol, iso-pinocamphone and trans-pinocarveol. The stability of 1 under the reaction conditions used was investigated by using FT-IR spectroscopy and electrospray ionisation mass spectrometry (ESI-MS) to characterise recovered solids. In the presence of air/moisture 1 undergoes oxidative decarbonylation upon dissolution to give oxomolybdenum species that are proposed to include a tetranuclear oxomolybdenum(v) complex. Conversely, ESI-MS studies of 1 dissolved in dry acetonitrile show mononuclear species of the type [IndMo(CO)2(CH3CN)n]+. The crystal structure of the ring-slipped dicarbonyl complex [(η3-Ind)Mo(CO)2Cl(CH3CN)2] (2) (obtained after dissolution of 1 in acetonitrile) is reported. [ABSTRACT FROM AUTHOR]