Structure revision of scytonemin imine and its relationship to scytonemin chromism and cyanobacterial adaptability.

Scytonemin, a UV-protective pigment produced by cyanobacteria, is essential for microbial survival under extreme solar radiation. Recent studies suggest its structural analog, scytonemin imine, may serve as a biosynthetic marker for cyanobacteria exposed to intense light. Here, we present a structural revision, revealing scytonemin imine as a cyclic hydropyrrolo[2,3-b]indole, rather than the previously proposed primary imine.

UVC-Intense Exoplanets May Not Be Uninhabitable: Evidence from a Desert Lichen.

Many of the recently discovered Earth-like exoplanets are hosted by M and F stars, stars that emit intense UVC, especially during a flare. We studied whether such planets are nevertheless habitable by irradiating a desert lichen, with 254-nm 55 W/m UVC nonstop for 3 months in the laboratory. Only 50% of its algal photobiont cells were inactivated.

H-NMR Guided Isolation of Bioactive Compounds from Species of the Genus .

The discovery of bioactive natural products is often challenged by the complexity of isolating and characterizing active compounds within diverse mixtures. Previously, we introduced a H NMR-based weighted gene correlation network analysis (WGCNA) approach to identify spectral features linked to growth inhibitory activity of () leaf extracts against model plant, fungal, and bacterial organisms. This method enabled us to prioritize specific spectral features linked to bioactivity, offering a targeted approach to natural product discovery.

Multiple and contrasting pressures determine intraspecific phytochemical variation in a tropical shrub.

Intraspecific phytochemical variation across a landscape can cascade up trophic levels, potentially mediating the composition of entire insect communities. Surprisingly, we have little understanding of the processes that regulate and maintain phytochemical variation within species, likely because these processes are complex and operate simultaneously both temporally and spatially. To assess how phytochemistry varies within species, we tested the degree to which resource availability, contrasting soil type, and herbivory generate intraspecific chemical variation in growth and defense of the tropical shrub, Piper imperiale (Piperaceae).

Discovery of octopamine and tyramine in nectar and their effects on bumblebee behavior.

Nectar chemistry can influence the behavior of pollinators in ways that affect pollen transfer, yet basic questions about how nectar chemical diversity impacts plant-pollinator relationships remain unexplored. For example, plants' capacity to produce neurotransmitters and endocrine disruptors may offer a means to manipulate pollinator behavior. We surveyed 15 plant species and discovered that two insect neurotransmitters, octopamine and tyramine, were widely distributed in floral nectar.

The chemical ecology of tropical forest diversity: Environmental variation, chemical similarity, herbivory, and richness.

Species richness in tropical forests is correlated with other dimensions of diversity, including the diversity of plant-herbivore interactions and the phytochemical diversity that influences those interactions. Understanding the complexity of plant chemistry and the importance of phytochemical diversity for plant-insect interactions and overall forest richness has been enhanced significantly by the application of metabolomics to natural systems. The present work used proton nuclear magnetic resonance spectroscopy ( H-NMR) profiling of crude leaf extracts to study phytochemical similarity and diversity among Piper plants growing naturally in the Atlantic Rainforest of Brazil.

Phytochemistry reflects different evolutionary history in traditional classes versus specialized structural motifs.

Foundational hypotheses addressing plant-insect codiversification and plant defense theory typically assume a macroevolutionary pattern whereby closely related plants have similar chemical profiles. However, numerous studies have documented variation in the degree of phytochemical trait lability, raising the possibility that phytochemical evolution is more nuanced than initially assumed. We utilize proton nuclear magnetic resonance (H NMR) data, chemical classification, and double digest restriction-site associated DNA sequencing (ddRADseq) to resolve evolutionary relationships and characterize the evolution of secondary chemistry in the Neotropical plant clade Radula (Piper; Piperaceae).

Elevated atmospheric concentrations of CO increase endogenous immune function in a specialist herbivore.

Animals rely on a balance of endogenous and exogenous sources of immunity to mitigate parasite attack. Understanding how environmental context affects that balance is increasingly urgent under rapid environmental change. In herbivores, immunity is determined, in part, by phytochemistry which is plastic in response to environmental conditions.

Secondary metabolites in a neotropical shrub: spatiotemporal allocation and role in fruit defense and dispersal.

Deciphering the ecological roles of plant secondary metabolites requires integrative studies that assess both the allocation patterns of compounds and their bioactivity in ecological interactions. Secondary metabolites have been primarily studied in leaves, but many are unique to fruits and can have numerous potential roles in interactions with both mutualists (seed dispersers) and antagonists (pathogens and predators). We described 10 alkenylphenol compounds from the plant species Piper sancti-felicis (Piperaceae), quantified their patterns of intraplant allocation across tissues and fruit development, and examined their ecological role in fruit interactions.

Proximity to canopy mediates changes in the defensive chemistry and herbivore loads of an understory tropical shrub, Piper kelleyi.

Phytochemical traits are a key component of plant defense theory. Chemical ecology has been biased towards studying effects of individual metabolites even though effective plant defenses are comprised of diverse mixtures of metabolites. We tested the phytochemical landscape hypothesis, positing that trophic interactions are contingent upon their spatial location across a phytochemically diverse landscape.

Shedding Light on Chemically Mediated Tri-Trophic Interactions: A H-NMR Network Approach to Identify Compound Structural Features and Associated Biological Activity.

Diverse mixtures of plant natural products play an important role in plant-herbivore-parasitoid interactions. In the pursuit of understanding these chemically-mediated interactions, we are often faced with the challenge of determining ecologically and biologically relevant compounds present in complex phytochemical mixtures. Using a network-based approach, we analyzed binned H-NMR data from 196 prepared mixtures of commonly studied secondary metabolites including alkaloids, amides, terpenes, iridoid glycosides, saponins, phenylpropanoids, flavonoids and phytosterols.

Similarity in volatile communities leads to increased herbivory and greater tropical forest diversity.

A longstanding paradigm in ecology is that there are positive associations between herbivore diversity, specialization, and plant species diversity, with a focus on taxonomic diversity. However, phytochemical diversity is also an informative metric, as insect herbivores interact with host plants not as taxonomic entities, but as sources of nutrients, primary metabolites, and mixtures of attractant and repellant chemicals. The present research examines herbivore responses to phytochemical diversity measured as volatile similarity in the tropical genus Piper.

Access to 4-Oxazolidinones: A (3 + 2) Cycloaddition Approach.

The novel reactivity of in situ generated aza-oxyallyl cation intermediates with a variety of carbonyl compounds is reported to construct 4-oxazolidinones motifs with good yields and diastereoselectivities. This simple and efficient (3 + 2) cycloaddition method provides direct access to potential bioactive compounds.

Intraspecific phytochemical variation shapes community and population structure for specialist caterpillars.

Chemically mediated plant-herbivore interactions contribute to the diversity of terrestrial communities and the diversification of plants and insects. While our understanding of the processes affecting community structure and evolutionary diversification has grown, few studies have investigated how trait variation shapes genetic and species diversity simultaneously in a tropical ecosystem. We investigated secondary metabolite variation among subpopulations of a single plant species, Piper kelleyi (Piperaceae), using high-performance liquid chromatography (HPLC), to understand associations between plant phytochemistry and host-specialized caterpillars in the genus Eois (Geometridae: Larentiinae) and associated parasitoid wasps and flies.

Oxidative (3 + 2) Cycloaddition Reactions of Diaza-Oxyallyl Cationic Intermediates and Indoles for the Synthesis of Imidazoloindolines.

An oxidative diaza-(3 + 2) cycloaddition reaction of simple urea derivatives with substituted indoles has been developed. This transformation provides rapid access to highly functionalized imidazoloindolines that are represented in bioactive compounds. The reported method is compatible with a wide variety of functional groups and directly provides unique heterocyclic scaffolds from indoles and a simple urea derivative.

Dearomative Indole Cycloaddition Reactions of Aza-Oxyallyl Cationic Intermediates: Modular Access to Pyrroloindolines.

A regioselective dearomative aza-(3 + 2) cycloaddition reaction of substituted indoles with α-halohydroxamates has been developed. This transformation provides rapid access to highly functionalized pyrroloindolines that are represented in large number of bioactive compounds. The natural product, physostigmine, has been concisely synthesized utilizing this method.

Phytochemical diversity drives plant-insect community diversity.

What are the ecological causes and consequences of variation in phytochemical diversity within and between plant taxa? Despite decades of natural products discovery by organic chemists and research by chemical ecologists, our understanding of phytochemically mediated ecological processes in natural communities has been restricted to studies of either broad classes of compounds or a small number of well-characterized molecules. Until now, no studies have assessed the ecological causes or consequences of rigorously quantified phytochemical diversity across taxa in natural systems. Consequently, hypotheses that attempt to explain variation in phytochemical diversity among plants remain largely untested.

Oxidative 1,4-diamination of dienes using simple urea derivatives.

Diamination of alkenes and dienes has found widespread use in the synthesis of biologically active target molecules. Although the 1,2-diamination of alkenes has been comprehensively explored, versatile methods that install higher order 1,n-diamine moieties (e.g.

New dimensions of tropical diversity: an inordinate fondness for insect molecules, taxa, and trophic interactions.

Most known insect species are involved in chemically mediated plant-insect multi-trophic interactions, and recent syntheses point to a substantial gap in our understanding of trophic interaction diversity, especially in the tropics. One approach to filling this gap is to examine relationships between genomic, metabolomic, taxonomic, and trophic interaction diversity via quantifying and comparing these dimensions of biodiversity at multiple scales. Innovative approaches to research on the origins and maintenance of tropical insect diversity should merge traditional approaches to natural history and taxonomy with modern measures of interaction diversity, genetic variation, and phytochemical diversity.

Age-dependent changes from allylphenol to prenylated benzoic acid production in Piper gaudichaudianum Kunth.

HPLC-DAD and principal component analysis (PCA) of the (1)H NMR spectrum of crude plant extracts showed high chemical variability among seedlings and adult organs of Piper gaudichaudianum. While gaudichaudianic acid was the major compound in the adult leaves, apiole and dillapiole were the major compounds in their seedling leaves. By the 15th month of seedling growth, the levels of apiole and dillapiole decreased and gaudichaudianic acid appeared along with two compounds, biosynthetically related to gaudichaudianic acid.

Antiherbivore prenylated benzoic acid derivatives from Piper kelleyi.

The known prenylated benzoic acid derivative 3-geranyl-4-hydroxy-5-(3″,3″-dimethylallyl)benzoic acid (1) and two new chromane natural products were isolated from the methanolic extract of the leaves of Piper kelleyi Tepe (Piperaceae), a midcanopy tropical shrub that grows in lower montane rain forests in Ecuador and Peru. Structure determination using 1D and 2D NMR analysis led to the structure of the chromene 2 and to the reassignment of the structure of cumanensic acid as 4, an isomeric chromene previously isolated from Piper gaudichaudianum. The structure and relative configuration of new chromane 3 was determined using 1D and 2D NMR spectroscopic analysis and was found to be racemic by ECD spectropolarimetry.

Cytotoxic non-aromatic B-ring flavanones from Piper carniconnectivum C. DC.

The EtOAc extract from the leaves of Piper carniconnectivum C. DC. was subjected to chromatographic separation to afford two non-aromatic B-ring flavanone compounds: 5-hydroxy-2-(1'-hydroxy-4'-oxo-cyclohex-2'-en-1'-yl)-6,7-dimethoxy-2,3-dihydro-4H-chromen-4-one (1) and 5-hydroxy-2-(1',2'-dihydroxy-4'-oxo-cyclohexyl)-6,7-dimethoxy-2,3-dihydro-4H-chromen-4-one (2).

1,4-Diamination of cyclic dienes via a (4 + 3) cycloaddition of diaza-allyl cationic intermediates.

Diaza-(4 + 3) cycloadditions of putative diaza-oxyallyl cationic intermediates and cyclic dienes are reported as a method for the 1,4-diamination of cyclic dienes. This reaction was entirely selective for diamination and provided cycloadducts in good to excellent yield.

Generation and reactivity of aza-oxyallyl cationic intermediates: aza-[4 + 3] cycloaddition reactions for heterocycle synthesis.

Aza-[4 + 3] cycloadditions of putative aza-oxyallyl cationic intermediates and cyclic dienes are reported. The intermediate is generated by the dehydrohalogenation of α-haloamides. The reaction is general to a variety of α-haloamides and is diastereoselective.

Dynamic kinetic resolution during a vinylogous Payne rearrangement: a concise synthesis of the polar pharmacophoric subunit of (+)-scyphostatin.

The diastereomeric epoxycyclohexenols 3a/b (obtained via a Wharton rearrangement of a bis-epoxycyclohexanone precursor) were shown to undergo interconversion via a facile vinylogous Payne rearrangement. Mechanistic issues were probed; the doubly O-deuterated analogues underwent this equilibration more slowly than the parent dihydroxy compounds. It was possible to kinetically resolve the mixture of 3a/b under equilibrating conditions by use of Amano PS.