Stefan Schulz

Technische Universität Braunschweig · Institute of Organic Chemistry

Steroid hormones are C18‐C21‐sterane derivatives, featuring the typical 6‐6‐6‐5 ring system. Here we report on a novel C18‐steroid ring system named batrachane with a contracted A‐ring resulting in a 5‐6‐6‐5 ring arrangement. The isolation, structural elucidation, and total synthesis of three members of the novel batrachopolyene family occurring in...

Background Previous studies have identified structurally diverse N-acyl amino acid methyl esters (NAMEs) in culture extracts of Roseovarius tolerans EL-164 (Roseobacteraceae). NAMEs are structural analogues of the common signaling compounds N-acyl homoserine lactones (AHLs), but do not participate in AHL-mediated signaling. NAMEs show minor antialg...

The secondary metabolites of springtails (Collembola) include defensive compounds, cuticular lipids, and semiochemicals, many of which are not known from other natural sources. The springtail chemistry differs largely from that of insects.

Springtails (Collembola) are important members of the soil mesofauna. They are small, often less than 1–2 mm in length. A typical escape response of most surface-living species is to jump, using their furca. However, some species also use chemical defence against predators. While the defence chemistry of higher insects has been well studied, report...

Innovative discovery approaches such as genome-mining and metabolomics-inspired methods have reshaped the natural product research field, complementing traditional bioactivity-based screens and allowing hitherto unseen compounds to be uncovered from previously investigated producers. In line with these trends, we report here imidacins, a novel clas...

A major question in evolutionary biology is what drives the diversification of lineages. Rapid, recent radiations are ideal systems for addressing how new species arise because they still show key morphological and ecological adaptations associated with speciation. While most studied recent radiations have evolved in an insular environment, less re...

Insect olfactory receptors are heteromeric ligand-gated cation channels composed of an obligatory receptor subunit, ORco, and one of many variable subunits, ORx, in as yet undefined molar ratios. When expressed alone ex vivo, ORco forms homotetrameric channels gated by ORco-specific ligands acting as channel agonists. Using an insect cell-based sys...

Synthetic routes to geosmin and its enantiomer are well established, but the enantioselective synthesis of stereoisomers of geosmin is unknown. Here a stereoselective synthesis of all stereoisomers of geosmin is...

Springtails (Collembola), tiny hexapod arthropods, are abundant in the soil of most ecosystems, but our knowledge of their secondary metabolites is limited, in contrast to that of insects. In insects, the outer cuticle is usually covered by mixtures of long-chain hydrocarbons serving different functions, such as water regulation or chemical communi...

Collembola are closely related to insects, but our knowledge of their often unique chemistry is limited. Here we report the identification of the epicuticular lipid nitidane, representing a novel class of epicuticular lipids. Nitidane (4) is an irregular terpene consisting of seven isoprene units, made up of a diterpene core that is modified by a g...

Hybridization allows adaptations to be shared among lineages and may trigger the evolution of new species1,2. However, convincing examples of homoploid hybrid speciation remain rare because it is challenging to demonstrate that hybridization was crucial in generating reproductive isolation³. Here we combine population genomic analysis with quantita...

Studies of adaptive radiations have played a central role in our understanding of reproductive isolation. Yet the focus has been on human-biased visual and auditory signals, leaving gaps in our knowledge of other modalities. To date, studies on chemical signals in adaptive radiations have focused on systems with multimodal signalling, making it dif...

Springtails use unique compounds for their outermost epicuticular wax layer, often of terpenoid origin. We report here the structure and synthesis of socialane, the major cuticular constituent of the Collembola Hypogastrura socialis. Socialane is also the first regular nonaprenyl terpene with a cyclic head group. The saturated side chain has seven...

Pheromone communication is widespread among animals. Since it is often involved in mate choice, pheromone production is often tightly controlled. Although male sex pheromones (MSPs) and anti-aphrodisiacs have been studied in some Heliconius butterfly species, little is known about the factors affecting their production and release in these long-liv...

The salinilactones, volatile marine natural products secreted from Salinispora arenicola, feature a unique [3.1.0]‐lactone ring system and cytotoxic activities through a hitherto unknown mechanism. To find their molecular target, an activity‐based protein profiling with a salinilactone‐derived probe is applied that disclosed the protein disulfide‐i...

The cypress bark beetle, Phloeosinus aubei, is of increasing concern in the European market of scale-leafed conifers. Neither the reproductive behaviour nor the chemical ecology have been studied in detail so far, and no specific attractant traps are available to monitor the flight of adults. We established that stridulation by males is crucial for...

Chemical signals serve a vast array of functions for both intra- and interspecific communication and defence. Chemically defended, aposematic insects will advertise their noxiousness to predators with warning signals and it has been suggested that volatile compounds shared between species could send a common signal to deter avian predators, similar...

The epicuticle of insects is usually coated with a complex mixture of hydrocarbons, primarily straight-chain and methyl-branched alkanes and alkenes. We were interested in whether springtails (Collembola), a sister class of the insects, also use such compounds. We focused here on Vertagopus sarekensis, an abundant Isotomidae species in European hig...

Male Heliconius butterflies possess two pheromone emitting structures, wing androconia and abdominal clasper scent glands. The composition of the clasper scent gland of males of 17 Heliconius and Eueides species from an overlapping area in Ecuador, comprising three mimicry groups, was investigated by GC/MS. The chemical signal serves as an anti‐aph...

In einer gemeinsamen Veranstaltung des Helmholtz‐Zentrums für Infektionsforschung (HZI) und der TU Braunschweig hielt Jörn Piel von der ETH Zürich am 8. Juni die Hans‐Herloff‐Inhoffen‐Vorlesung.

In contrast to many other water birds, the Great Cormorant, Phalacrocorax carbo (Phalacrocoracidae), shows a typical wing-spreading behavior after diving. This behavior has been linked to the partial wettability of the Cormorant’s feathers based on the unusual structure of the contour feathers. Close to the rachis, these feathers have a closed vane...

Guest editor Stefan Schulz introduces this Natural Products Reports themed issue summarizing recent progress in volatile natural products.

Outer Membrane Vesicles (OMVs) of the Gram-negative marine bacterium Dinoroseobacter shibae, a member of the Roseobacteraceae, were investigated for the presence of volatile organic compounds (VOCs). Extracts of vesicles were analyzed by gas chromatography/mass spectrometry (GC/MS). In these analyses the short fatty acid (Z)-5-dodecenoic acid (1) a...

The cypress bark beetle, Phloeosinus aubei Perris (Coleoptera: Curculionidae, Scolytinae), is of increased concern in the European market of scale-leafed conifers (Cupressaceae). Surprisingly, its chemical communication has only scarcely been studied and no specific trap-based monitoring system is available for detection of flight of the adults. In...

Hyperolid reed frogs are one of the few families of Anurans known to possess glands that emit volatile compounds used in chemical communication. Hyperolius cinnamomeoventris , a model species, possesses a gular gland on its vocal sac that emits chemicals, and sends visual and auditory signals during calling. Previous investigations have shown that...

Volatiles released by the apicomplexan alga Chromera velia CCAP1602/1 and their associated bacteria have been investigated. A metagenome analysis allowed the identification of the most abundant heterotrophic bacteria of the phycosphere, but the isolation of additional strains showed that metagenomics underestimated the complexity of the algal micro...

Covering: 1990 up to 2022 Contrary to popular opinion, butterflies exhibit a rich chemistry and elaborate use of volatile compounds, especially for sexual communication, but also for defence. In contrast to night flying moths, in which commonly females are the producers of pheromones, male scent emission is prevalent in butterflies. While visual si...

The cypress bark beetle, Phloeosinus aubei Perris (Coleoptera: Curculionidae, Scolytinae), is of increased concern in the market of scale-leafed conifers (Cupressaceae), across a wide range of its expansion area in Europe. Surprisingly, its pheromonal communication has only scarcely been studied no specific trap-based monitoring system is available...

Many plant species are pollinated by butterflies. These insects are primarily attracted by visual flower cues, however, butterflies are also known to respond to flower scents and some butterfly-pollinated plants are strongly scented. One of such plants is the butterfly bush, Buddleja davidii, which is a magnet for butterflies. It is widespread in i...

During courtship, male butterflies of many species produce androconial secretions containing male sex pheromones (MSPs) that communicate species identity and affect female choice. MSPs are thus likely candidates as reproductive barriers, yet their role in speciation remains poorly studied. Although Heliconius butterflies are a model system in speci...

Clostridioides difficile (previously Clostridium difficile ) causes life-threatening gut infections. The central metabolism of the bacterium is strongly influencing toxin production and consequently the infection progress. In this context, the composition and potential origin of the volatile metabolome was investigated, showing a large number of su...

Frogs of the families Mantellinae and Hyperoliidae possess male specific femoral or gular glands that are used during courtship. These glands release volatile compounds, e. g. the macrocyclic lactone gephyromantolide A (2,6,10-trimethyl-6-undecen-11-olide) in the case of Gephyromantis boulengeri (Mantellinae). During the analysis of the volatiles o...

The dinoflagellate Prorocentrum cordatum, often called P. minimum, is a potentially toxic alga found in algal blooms. Volatile compounds released by the alga might carry important information, e.g., on its physiological state, and may act as chemical messengers. We report here the identification of volatile organic compounds emitted by two strains,...

Investigation of the contents of the scent glands of the heliconiine butterfly Heliconius erato phyllis via gas chromatography/electroantennography revealed an unprecedented active compound. The males transfer this compound to females during mating. The structure of (2R,6E,10R)-2,6-dimethyl-6-undecen-10-olide, a derivative of geranylacetone, was pr...

Heliconius erato is a neotropical butterfly species that is part of a complex mimicry ring, with colorful wing patterns. For intraspecific communication, males use pheromones that are released from two different scent-emitting structures. Scent glands located near the abdominal claspers of males, containing antiaphrodisiac pheromones, release a hig...

MACE is an open access collection of electron impact (EI) mass spectra for coupled gas chromatography-mass spectrometry (GC/MS) that serves as an add-on database, comprising curated spectra not present in widely available commercial mass spectral libraries, such as the NIST or WILEY databases. The spectra are stored as text files that allow easy in...

Insect repellents are important means of personal protection against bites from mosquitoes carrying various pathogens. Odorant-dependent behaviours are triggered by odor ligands bound to odorant receptors. Insect odorant receptors are heterotetrameric ligand-gated cation channels composed of an obligatory subunit, ORco, and one of many variable sub...

Frogs of the families Mantellinae and Hyperoliidae possess male specific femoral or gular glands that are used during courtship. These glands release volatile compounds, e. g. the macrocyclic lactone gephyromantolide A (2,6,10-trimethyl-6-undecen-11-olide) in the case of Gephyromantis boulengeri (Mantellinae). During the analysis of the volatiles o...

Emerging evidence shows that the cuticular and silk lipids of spiders are structurally more diverse than those of insects, although only a relatively low number of species have been investigated so far. As in insects, such lipids might play a role as signals in various contexts. The wasp spider Argiope bruennichi has probably the best investigated...

Unser Mitglied Prof. Dr. Dr. h.c. mult. Wittko Francke verstarb völlig unerwartet am 27.12.2020 in Hamburg im Alter von 80 Jahren an einer SARS-Cov-2-Infektion. Noch aus dem Krankenhaus gab er Korrekturanweisungen für Manuskripte, obwohl er bereits mit dem Tode kämpfte. Wer war diese außergewöhnliche Persönlichkeit?

The butterfly Heliconius erato occurs in various mimetic morphs. The male clasper scent gland releases an anti‐aphrodisiac pheromone and additionally contains a complex mixture of up to 350 components, varying between individuals. In 114 samples of five different mimicry groups and their hybrids 750 different compounds were detected by gas chromato...

Chemical communication plays a fundamental role in many aspects of an animal's life from assessing habitat quality to finding mating partners. Behavioural observations show that chemical communication likewise plays an important role in spiders, but the contexts and the substances involved are little explored. Here, we investigate the chemical comm...

P. inhibens 2.10 is an effective biofilm former on marine surfaces and has the ability to outcompete other microorganisms, possibly due to the production of the plasmid-encoded, secondary metabolite tropodithietic acid (TDA). P. inhibens 2.10 biofilms produce phenotypic variants with reduced competitiveness compared to the wild-type. In the present...

Am 27. Dezember 2020 starb Wittko Francke, Professor für Organische Chemie. Sein zentrales Forschungsgebiet war die chemische Ökologie.

Emerging evidence shows that the cuticular and silk lipids of spiders are structurally more diverse than those of insects, although only a relatively low number of species have been investigated so far. As in insects, such lipids might play a role as signals in various context. The wasp spider Argiope bruennichi has probably the best investigated c...

Secondary metabolites are key components in microbial ecology by mediating interactions between bacteria and their environment, neighboring species or host organisms. Bioactivities can be beneficial for both interaction partners or provide a competitive advantage only for the producer. Colonizers of confined habitats such as biofilms are known as p...

In eusocial insects, chemical communication is crucial for mediating many aspects of social activities, especially the regulation of reproduction. Though queen signals are known to decrease ovarian activation of workers in highly eusocial species, little is known about their evolution. In contrast, some primitively eusocial species are thought to c...

The esteemed member of the German Society for General and Applied Entomology (DGaaE), Prof. Dr. Dr. h. c. mult. Wittko Francke, died unexpectedly on 27 December 2020 in Hamburg at the age of 80 from a SARS-Cov-2 infection. Even from the hospital, he gave corrective instructions for manuscripts, although he was already struggling with death. Who was...

Significance Individual cells within a community often need to respond to changing environmental conditions at the population level. Accordingly, bacteria have evolved a large array of regulatory mechanisms that enable them to quickly reprogram behavior in a coordinated manner. Unraveling these mechanisms provides valuable information regarding col...

The uncommon jasmone derivatives dehydrojasmone, isojasmol, and isojasmyl acetate, floral scent compounds from night-blooming Araceae, were synthesized in a scalable synthesis employing conjugate addition with a selenoacetal as the key step. The stereoselective strategy with subsequent enzymatic kinetic resolution allowed determining the absolute c...

For a long time, frogs were believed to communicate primarily via the acoustic channel, but during the last decades it became obvious that various lineages also use chemical communication. In this Account we present our research on the identification of volatile lactones from Madagascan Mantellidae and African Hyperoliidae frogs. Both possess male...

Microorganisms produce and excrete a versatile array of metabolites with different physico-chemical properties and biological activities. However, the ability of microorganisms to release volatile compounds has only attracted research attention in the past decade. Recent research has revealed that microbial volatiles are chemically very diverse and...

Plants and insects often use the same compounds for chemical communication, but not much is known about the genetics of convergent evolution of chemical signals. The terpene (E)-β-ocimene is a common component of floral scent and is also used by the butterfly Heliconius melpomene as an anti-aphrodisiac pheromone. While the biosynthesis of terpenes...

Much of our knowledge regarding the role of chemicals in species recognition in arthropods is based on a few taxonomic groups, predominantly insect pest species. To investigate the chemical underpinnings of species recognition cues in other arthropods, we conducted mate choice experiments and analyzed the chemical profiles of two species in the lon...

Male ithomiine butterflies (Nymphalidae: Danainae) have hairpencils on the forewings (i.e., androconia) that disseminate semio-chemicals during courtship. While most ithomiines are known to contain derivatives of pyrrolizidine alkaloids, dihydropyrrolizines, or γ-lactones in these androconia, here we report on a new class of fatty acid esters ident...

The genus Pseudooceanicola from the alphaproteobacterial Roseobacter group currently includes ten validated species. We herein describe strain Lw-13eT, the first Pseudooceanicola species from marine macroalgae, isolated from the brown alga Fucus spiralis abundant at European and North American coasts. Physiological and pangenome analyses of Lw-13eT...

The degree to which loci promoting reproductive isolation cluster in the genome—that is, the genetic architecture of reproductive isolation—can influence the tempo and mode of speciation. Tight linkage between these loci can facilitate speciation in the face of gene flow. Pheromones play a role in reproductive isolation in many Lepidoptera species,...

Odorant-dependent behaviors in insects are triggered by the binding of odorant ligands to the variable subunits of heteromeric olfactory receptors. Previous studies have shown, however, that specific odor binding to ORco, the common subunit of odorant receptor heteromers, may allosterically alter olfactory receptor function and profoundly affect su...

Cell-cell fusion is crucial for the development and propagation of most eukaryotic organisms. Despite this importance, the molecular mechanisms mediating this process are only poorly understood in any biological system. In particular, the step of plasma membrane merger and the contributing proteins and physicochemical factors remain mostly unknown....

Bacterial volatile organic compounds (VOCs) represent a structurally very broad mixture of compounds, likely not less diverse than plant or animal volatiles. Within this diversity individual compounds might be commonly found in many, often unrelated strains, while others are restricted to a certain group of strains. In addition, strain specific com...