The Jubilee of Methyl Jasmonate and Hedione®

Development of an efficient and scalable bioprocess for the plant hormone 12-OPDA: Overcoming the hurdles of nature's biosynthesis

Besides its native biological function as a plant hormone, cis-(+)-12-oxo-phytodienoic acid (12-OPDA) serves as a metabolite for the cellular formation of (-)-jasmonic acid and has also been shown to have an influence on mammalian cells. In order to make this biologically active, but at the same time very expensive natural product 12-OPDA broadly accessible for further biological and medicinal research, we developed an efficient bioprocess based on the utilization of a tailor-made whole-cell catalyst by following the principles of its biosynthesis in nature. After process optimization, the three-step one-pot synthesis of 12-OPDA starting from readily accessible α-linolenic acid could be conducted at appropriate technically relevant substrate loadings in the range of 5-20 g L-1. The desired 12-OPDA was obtained with an excellent conversion efficiency, and by means of the developed, efficient downstream-processing, this emulsifying as well as stereochemically labile biosynthetic metabolite 12-OPDA was then obtained with very high chemical purity (>99%) and enantio- and diastereomeric excess (>99% ee, 96% de) as well as negligible side-product formation (<1%). With respect to future technical applications, we also demonstrated the scalability of the production of the whole cell-biocatalyst in a high cell-density fermentation process.

Diastereoselective Hydrogenation of Tetrasubstituted Olefins using a Heterogeneous Pt-Ni Alloy Catalyst

Stereoselective hydrogenation of tetrasubstituted olefins is an attractive method to access compounds with two contiguous stereocenters. However, homogeneous catalysts for enantio- and diastereoselective hydrogenation exhibit low reactivity toward tetrasubstituted olefins due to steric crowding between the ligand scaffold and the substrate. Monometallic heterogeneous catalysts, on the other hand, provide accessible surface active sites for hindered olefins but exhibit unpredictable and inconsistent stereoinduction. In this work, we develop a Pt-Ni bimetallic alloy catalyst that can diastereoselectively hydrogenate unactivated, sterically-bulky tetrasubstituted olefins, utilizing the more oxophilic Ni atoms to adsorb a hydroxyl directing group and direct facially-selective hydrogen addition to the olefin via the Pt atoms. Structure-activity studies on several Pt-Ni compositions underscore the importance of exposing a uniform PtNi alloy surface to achieve high diastereoselectivity and minimize side reactions. The optimized Pt-Ni/SiO2 catalyst exhibits good functional group tolerance and broad scope for tetrasubstituted olefins in a cyclopentene scaffold, generating cyclopentanol products with three contiguous stereocenters. The synthetic utility of the method is demonstrated in a four-step synthesis of (1R,2S)-(+)-cis-methyldihydrojasmonate with high yield and enantiopurity.

High production of jasmonic acid by Lasiodiplodia iranensis using solid-state fermentation: Optimization and understanding

BACKGROUND

Jasmonic acid (JA) is a plant hormone involved in regulating developmental and growth controls as well as photosynthesis. In addition, this hormone protects the plant against insects and has good applications in agriculture, the flavored industry and other fields. Filamentous fungus generally produces JA using liquid static culture. In the present study, a solid-state fermentation (SSF) method is developed for high production of JA using Lasiodiplodia iranensis.

MAIN METHODS AND MAJOR RESULTS

By selecting the solid substrate and optimizing the initial water content, inoculum volume, loading volume and other culture conditions, the maximum JA yield reached 5306.38 mg/kg when fermented for 12 days in a petri dish containing a medium with crushed wheat as the solid substrate and 75% initial water content. The logistic and Luedeking-Piret models were used to characterize the relationship between microbial growth and product synthesis in the SSF process, and the maximum JA production is predicted to be 5263.23 mg/kg, which is close to the experimental value. Liquid chromatography with tandem mass spectrometry (LC-MS/MS) is used to examine the metabolic changes that develop during fermentation. The results indicate that JA biosynthesis occurs in the α-linolenic acid metabolic pathway, of which 13(S)-HpOTrE is a key intermediate metabolite and both 13(S)-HOTrE and traumatic acid are byproducts of the branches of its synthesis.

CONCLUSIONS AND IMPLICATIONS

The results of this study provide a method for obtaining high JA yields by SSF, and offer new insights for understanding the production of JA by fungal fermentation. This article is protected by copyright. All rights reserved.

Practical Enzymatic Production of Carbocycles

The Pd-catalyzed carbon-carbon bond formation pioneered by Heck in 1969 has dominated medicinal chemistry development for the ensuing fifty years. As the demand for more complex three-dimensional active pharmaceuticals continues to increase, preparative enzyme-mediated assembly, by virtue of its exquisite selectivity and sustainable nature, is poised to provide a practical and affordable alternative for accessing such compounds. In this minireview, we summarize recent state-of-the-art developments in practical enzyme-mediated assembly of carbocycles. When appropriate, background information on the enzymatic transformation is provided and challenges and/or limitations are also highlighted.

Prior exposure to Hedione, a model of pheromone, does not affect female ratings of male facial attractiveness or likeability

The existence of pheromones in humans is controversial, partly because of definitional difficulties and partly because of the question of possible chemical substances. The synthetic compound Methyl dihydrojasmonate (Hedione) is potent to bind to vomeronasal-type 1 receptors (VN1R1s) and activate limbic areas of the brain in a sex-specific manner. However, one of the most important definitional points for a human pheromone effect has not yet been investigated, i.e., whether smelling Hedione, a model of pheromone, has a behavioral effect. We tested in females whether Hedione leads to altered perception of male social stimuli. Each of the included women were sensitive to Hedione and were tested around the time of ovulation in three consecutive sessions, during each they were exposed to either Hedione or Phenylethyl alcohol or Odorless air. We measured the speed of male face recognition (implicit priming task) and collected ratings of facial attractiveness and likeability of men (explicit task). Only about half of the women tested were sensitive to Hedione. Those women did not show any effect of Hedione exposure in the implicit priming task and moderate, but non-significant effects in the explicit task. We therefore assume that Hedione is not a potent model of pheromone in humans and this observation may be due to the fact that the artificially produced substance is not suited for signaling the proximity of other humans. Furthermore, the high rate of Hedione-specific anosmia leads to the hypothesis that a substantial proportion of individuals has a poor V1NR1 receptor expression.

The Effects of Post-Harvest Treatments on the Quality of Agastache aurantiaca Edible Flowers

Agastache spp. are used as ornamental plants for their pleasant aroma and the different colors of flowers. Nowadays, their edible flowers have become attractive for their nutraceutical properties. Post-harvest treatment appears as a crucial point to avoid impairment of the nutraceutical compounds and aroma, so different treatments were tested to analyze their effect on the bioactive metabolites and volatilome. Results indicated that freeze-drying was the best solution to prolong the shelf life of these flowers. The use of high temperatures (50, 60, 70 °C) led to altered the composition of antioxidant compounds (phenolic compounds, flavonoids, anthocyanins, carotenoids). Air-drying at 30 °C was a reasonable method, even though time consuming. Concerning the aroma profile, all samples were dominated by oxygenated monoterpene compounds. Pulegone was the main or one of the major constituents of all samples together with p-menthone. Gas Chromatography-Mass Spectrometry results showed a correlation between the temperature and the number of identified compounds. Both fresh and freeze-dried samples evidenced a lesser number (10 and 19, respectively); when the temperature raised, the number of identified constituents increased. Statistical analyses highlighted significant differences between almost all aromatic compounds, even if both Principal Component and Hierarchical Cluster analyses differed at 60 and 70 °C and from the other treatments.

The Smelling Principle of Vetiver Oil, Unveiled by Chemical Synthesis

Vetiver oil, produced on a multiton‐scale from the roots of vetiver grass, is one of the finest and most popular perfumery materials, appearing in over a third of all fragrances. It is a complex mixture of hundreds of molecules and the specific odorant, responsible for its characteristic suave and sweet transparent, woody‐ambery smell, has remained a mystery until today. Herein, we prove by an eleven‐step chemical synthesis, employing a novel asymmetric organocatalytic Mukaiyama–Michael addition, that (+)‐2‐epi‐ziza‐6(13)en‐3‐one is the active smelling principle of vetiver oil. Its olfactory evaluation reveals a remarkable odor threshold of 29 picograms per liter air, responsible for the special sensuous aura it lends to perfumes and the quasi‐pheromone‐like effect it has on perfumers and consumers alike.

Jasmonic acid biosynthesis by fungi: derivatives, first evidence on biochemical pathways and culture conditions for production

Jasmonic acid (JA) and its derivatives called jasmonates (JAs) are lipid-derived signalling molecules that are produced by plants and certain fungi. Beside this function, JAs have a great variety of applications in flavours and fragrances production. In addition, they may have a high potential in agriculture. JAs protect plants against infections. Although there is much information on the biosynthesis and function of JA concerning plants, knowledge on these aspects is still scarce for fungi. Taking into account the practical importance of JAs, the objective of this review is to summarize knowledge on the occurrence of JAs from fungal culture media, their biosynthetic pathways and the culture conditions for optimal JA production as an alternative source for the production of these valuable metabolites.

From a Biosynthetic Pathway toward a Biocatalytic Process and Chemocatalytic Modifications: Three-Step Enzymatic Cascade to the Plant Metabolite cis-(+)-12-OPDA and Metathesis-Derived Products

A biotechnological approach toward the plant metabolite and regulator cis-(+)-12-oxophytodienoic acid (cis-(+)-12-OPDA) in a one-pot process with >99% conversion, at least 90% selectivity and ≤10% of side products as well as a high diastereoselectivity (leading to d.r. of at least 90:10) is reported. The optimized organic-synthetic enzyme cascade for preparing this bioactive and commercial molecule with pharmaceutical relevance on a gram per L scale is designed based on its biosynthetic pathway starting from cheap and readily accessible linolenic acid. Toward this end, a recombinant biocatalyst system has been prepared for carrying out the most critical two key steps in a tailored manner, thus avoiding sensitive intermediate decomposition. Furthermore, cis-(+)-12-OPDA is successfully modified via a cross-alkene metathesis reaction with conversions of up to >99%, leading to a compound library of new cis-(+)-12-OPDA derivatives with different substitution pattern of the side chain at the 2-position. By means of such a combined biotechnological and chemocatalytic route, a straightforward approach to a structurally unique oxylipin library is realized, which would be highly difficult or not accessible by pure chemical and biotechnological methods, respectively.

Methyl dihydrojasmonate and lilial are the constituents with an "off-label" insect repellence in perfumes

Insect repellents are widely used to fend off nuisance mosquitoes and, more importantly, to reduce or eliminate mosquito bites in areas where viruses and other vector-borne diseases are circulating. Synthesized more than six decades ago, DEET is the most widely used insect repellent. Plant-derived compounds are used in a plethora of commercial formulations and natural recipes to repel mosquitoes. They are also used as fragrances. We analysed Bombshell^® to identify the constituent(s) eliciting a previously reported “off- label” repellence activity. The two major fragrance ingredients in Bombshell, i.e., methyl dihydrojasmonate and lilial, demonstrated strong repellence against the southern house mosquito, Culex quinquefasciatus, in laboratory assays. Both compounds activated a previously identified DEET-sensitive odorant receptor, CquiOR136. These compounds were also major constituents of Ivanka Trump eau de parfum. The methyl dihydrojasmonate content was higher in the Ivanka Trump perfume than in Bombshell, the reverse being true for lilial. Both Bombshell and Ivanka Trump eaux de parfums retained activity for as long as 6 hours in laboratory assays. Although wearing these perfumes may repel nuisance mosquitoes, their use as “off-label” repellents against infected mosquitoes is not recommended.

Efficient Synthesis of the Cyclopentanone Fragrances (Z)-3-(2-oxopropyl)-2-(pent-2-en-1-yl)cyclopentanone and Magnolione

This paper describes the selective syntheses of two cis-isomer enriched cyclopentanone fragrances: (Z)-3-(2-oxopropyl)-2-(pent-2-en-1-yl)cyclopentanone (4 steps, 62% overall yield, 67% cis) and Magnolione^® (5 steps, 60% overall yield, 55% cis). In addition, the asymmetric synthesis of (3aR,7aS)-5-methyl-2,3,3a,4,7,7a-hexahydro-1H-inden-1-one as well as (3a'R,7a'S)-5'-methyl-2',3',3a',4',7',7a'-hexahydrospiro[[1,3]dioxolane-2,1'-indene]) has been realized by an efficient kinetic resolution, which enables the selective synthesis of the 2S,3R-isomer-enriched 3 and 4.