What one genus of showy moths can say about migration, adaptation, and wing pattern.

The Ornate Moth, Utetheisa ornatrix, has served as a model species in chemical ecology studies for decades. Like in the widely publicized stories of the Monarch and other milkweed butterflies, the Ornate Moth and its relatives are tropical insects colonizing whole continents assisted by their chemical defenses. With the recent advances in genomic techniques and evo-devo research, it is becoming a model for studies in other areas, from wing pattern development to phylogeography, from toxicology to epigenetics. We used a genomic approach to learn about Utetheisa's evolution, detoxification, dispersal abilities, and wing pattern diversity. We present an evolutionary genomic analysis of the worldwide genus Utetheisa, then focusing on U. ornatrix. Our reference genome of U. ornatrix reveals gene duplications in the regions possibly associated with detoxification abilities, which allows them to feed on toxic food plants. Finally, comparative genomic analysis of over 100 U. ornatrix specimens from the museum with apparent differences in wing patterns suggest the potential roles of cortex and lim3 genes in wing pattern formation of Lepidoptera and the utility of museum-preserved collection specimens for wing pattern research.

Evolution and diversification of carboxylesterase-like [4+2] cyclases in aspidosperma and iboga alkaloid biosynthesis.

Monoterpene indole alkaloids (MIAs) are a large and diverse class of plant natural products, and their biosynthetic construction has been a subject of intensive study for many years. The enzymatic basis for the production of aspidosperma and iboga alkaloids, which are produced exclusively by members of the Apocynaceae plant family, has recently been discovered. Three carboxylesterase (CXE)-like enzymes from Catharanthus roseus and Tabernanthe iboga catalyze regio- and enantiodivergent [4+2] cycloaddition reactions to generate the aspidosperma (tabersonine synthase, TS) and iboga (coronaridine synthase, CorS; catharanthine synthase, CS) scaffolds from a common biosynthetic intermediate. Here, we use a combined phylogenetic and biochemical approach to investigate the evolution and functional diversification of these cyclase enzymes. Through ancestral sequence reconstruction, we provide evidence for initial evolution of TS from an ancestral CXE followed by emergence of CorS in two separate lineages, leading in turn to CS exclusively in the Catharanthus genus. This progression from aspidosperma to iboga alkaloid biosynthesis is consistent with the chemotaxonomic distribution of these MIAs. We subsequently generate and test a panel of chimeras based on the ancestral cyclases to probe the molecular basis for differential cyclization activity. Finally, we show through partial heterologous reconstitution of tabersonine biosynthesis using non-pathway enzymes how aspidosperma alkaloids could have first appeared as "underground metabolites" via recruitment of promiscuous enzymes from common protein families. Our results provide insight into the evolution of biosynthetic enzymes and how new secondary metabolic pathways can emerge through small but important sequence changes following co-option of preexisting enzymatic functions.

Elucidation of the 1-phenethylisoquinoline pathway from an endemic conifer Cephalotaxus hainanensis.

Cephalotaxines harbor great medical potential, but their natural source, the endemic conifer Cephalotaxus is highly endangered, creating a conflict between biotechnological valorization and preservation of biodiversity. Here, we construct the whole biosynthetic pathway to the 1-phenethylisoquinoline scaffold, as first committed compound for phenylethylisoquinoline alkaloids (PIAs), combining metabolic modeling, and transcriptome mining of Cephalotaxus hainanensis to infer the biosynthesis for PIA precursor. We identify a novel protein, ChPSS, driving the Pictet-Spengler condensation and show that this enzyme represents the branching point where PIA biosynthesis diverges from the concurrent benzylisoquinoline-alkaloids pathway. We also pinpoint ChDBR as crucial step to form 4-hydroxydihydrocinnamaldehyde diverging from lignin biosynthesis. The elucidation of the early PIA pathway represents an important step toward microbe-based production of these pharmaceutically important alkaloids resolving the conflict between biotechnology and preservation of biodiversity.

Genomic and structural basis for evolution of tropane alkaloid biosynthesis.

The tropane alkaloids (TAs) cocaine and hyoscyamine have been used medicinally for thousands of years. To understand the evolutionary origins and trajectories of serial biosynthetic enzymes of TAs and especially the characteristic tropane skeletons, we generated the chromosome-level genome assemblies of cocaine-producing Erythroxylum novogranatense (Erythroxylaceae, rosids clade) and hyoscyamine-producing Anisodus acutangulus (Solanaceae, asterids clade). Comparative genomic and phylogenetic analysis suggested that the lack of spermidine synthase/N-methyltransferase (EnSPMT1) in ancestral asterids species contributed to the divergence of polyamine (spermidine or putrescine) methylation in cocaine and hyoscyamine biosynthesis. Molecular docking analysis and key site mutation experiments suggested that ecgonone synthases CYP81AN15 and CYP82M3 adopt different active-site architectures to biosynthesize the same product ecgonone from the same substrate in Erythroxylaceae and Solanaceae. Further synteny analysis showed different evolutionary origins and trajectories of CYP81AN15 and CYP82M3, particularly the emergence of CYP81AN15 through the neofunctionalization of ancient tandem duplication genes. The combination of structural biology and comparative genomic analysis revealed that ecgonone methyltransferase, which is responsible for the biosynthesis of characteristic 2-substituted carboxymethyl group in cocaine, evolved from the tandem copies of salicylic acid methyltransferase by the mutations of critical E216 and S153 residues. Overall, we provided strong evidence for the independent origins of serial TA biosynthetic enzymes on the genomic and structural level, underlying the chemotypic convergence of TAs in phylogenetically distant species.

Seeing double: two different homospermidine oxidases are involved in pyrrolizidine alkaloid biosynthesis in different organs of comfrey (Symphytum officinale).

Pyrrolizidine alkaloids (PAs) are toxic specialized metabolites produced in several plant species and frequently contaminate herbal teas or livestock feed. In comfrey (Symphytum officinale, Boraginaceae), they are produced in two different organs of the plant, the root and young leaves. In this study, we demonstrate that homospermidine oxidase (HSO), a copper-containing amine oxidase (CuAO) responsible for catalyzing the formation of the distinctive pyrrolizidine ring in PAs, is encoded by two individual genes. Specifically, SoCuAO1 is expressed in young leaves, while SoCuAO5 is expressed in roots. CRISPR/Cas9-mediated knockout of socuao5 resulted in hairy roots (HRs) unable to produce PAs, supporting its function as HSO in roots. Plants regenerated from socuao5 knockout HRs remained completely PA-free until the plants began to develop inflorescences, indicating the presence of another HSO that is expressed only during flower development. Stable expression of SoCuAO1 in socuao5 knockout HRs rescued the ability to produce PAs. In vitro assays of both enzymes transiently expressed in Nicotiana benthamiana confirmed their HSO activity and revealed the ability of HSO to control the stereospecific cyclization of the pyrrolizidine backbone. The observation that the first specific step of PA biosynthesis catalyzed by homospermidine synthase requires only one gene copy, while two independent paralogs are recruited for the subsequent homospermidine oxidation in different tissues of the plant, suggests a complex regulation of the pathway. This adds a new level of complexity to PA biosynthesis, a system already characterized by species-specific, tight spatio-temporal regulation, and independent evolutionary origins in multiple plant lineages.

The role of ABCC10/MRP7 in anti-cancer drug resistance and beyond.

Multidrug resistance protein 7 (MRP7), also known as ATP-binding cassette (ABC) transporter subfamily C10 (ABCC10), is an ABC transporter that was first identified in 2001. ABCC10/MRP7 is a 171 kDa protein located on the basolateral membrane of cells. ABCC10/MRP7 consists of three transmembrane domains and two nucleotide binding domains. It mediates multidrug resistance of tumor cells to a variety of anticancer drugs by increasing drug efflux and results in reducing intracellular drug accumulation. The transport substrates of ABCC10/MRP7 include antineoplastic drugs such as taxanes, vinca alkaloids, and epothilone B, as well as endobiotics such as leukotriene C4 (LTC4) and estradiol 17 ß-D-glucuronide. A variety of ABCC10/MRP7 inhibitors, including cepharanthine, imatinib, erlotinib, tariquidar, and sildenafil, can reverse ABCC10/MRP7-mediated MDR. Additionally, the presence or absence of ABCC10/MRP7 is also closely related to renal tubular dysfunction, obesity, and other diseases. In this review, we discuss: 1) Structure and functions of ABCC10/MRP7; 2) Known substrates and inhibitors of ABCC10/MRP7 and their potential therapeutic applications in cancer; and 3) Role of ABCC10/MRP7 in non-cancerous diseases.

Characterization of CYP82 genes involved in the biosynthesis of structurally diverse benzylisoquinoline alkaloids in Corydalis yanhusuo.

Benzylisoquinoline alkaloids (BIAs) represent a significant class of secondary metabolites with crucial roles in plant physiology and substantial potential for clinical applications. CYP82 genes are involved in the formation and modification of various BIA skeletons, contributing to the structural diversity of compounds. In this study, Corydalis yanhusuo, a traditional Chinese medicine rich in BIAs, was investigated to identify the catalytic function of CYP82s during BIA formation. Specifically, 20 CyCYP82-encoding genes were cloned, and their functions were identified in vitro. Ten of these CyCYP82s were observed to catalyze hydroxylation, leading to the formation of protopine and benzophenanthridine scaffolds. Furthermore, the correlation between BIA accumulation and the expression of CyCYP82s in different tissues of C. yanhusuo was assessed their. The identification and characterization of CyCYP82s provide novel genetic elements that can advance the synthetic biology of BIA compounds such as protopine and benzophenanthridine, and offer insights into the biosynthesis of BIAs with diverse structures in C. yanhusuo.

Genome-wide identification of GATA transcription factor family and the effect of different light quality on the accumulation of terpenoid indole alkaloids in Uncaria rhynchophylla.

Uncaria rhynchophylla is an evergreen vine plant, belonging to the Rubiaceae family, that is rich in terpenoid indole alkaloids (TIAs) that have therapeutic effects on hypertension and Alzheimer's disease. GATA transcription factors (TF) are a class of transcription regulators that participate in the light response regulation, chlorophyll synthesis, and metabolism, with the capability to bind to GATA cis-acting elements in the promoter region of target genes. Currently the charactertics of GATA TFs in U. rhynchophylla and how different light qualities affect the expression of GATA and key enzyme genes, thereby affecting the changes in U. rhynchophylla alkaloids have not been investigated. In this study, 25 UrGATA genes belonging to four subgroups were identified based on genome-wide analysis. Intraspecific collinearity analysis revealed that only segmental duplications were identified among the UrGATA gene family. Collinearity analysis of GATA genes between U. rhynchophylla and four representative plant species, Arabidopsis thaliana, Oryza sativa, Coffea Canephora, and Catharanthus roseus was also performed. U. rhynchophylla seedlings grown in either red lights or under reduced light intensity had altered TIAs content after 21 days. Gene expression analysis reveal a complex pattern of expression from the 25 UrGATA genes as well as a number of key TIA enzyme genes. UrGATA7 and UrGATA8 were found to have similar expression profiles to key enzyme TIA genes in response to altered light treatments, implying that they may be involved in the regulation TIA content. In this research, we comprehensively analyzed the UrGATA TFs, and offered insight into the involvement of UrGATA TFs from U. rhynchophylla in TIAs biosynthesis.

Naphthylisoquinoline alkaloids: novel agents against the causative pathogens of eumycetoma and actinomycetoma-en route to broad-spectrum antimycetomal drugs.

Mycetoma is a devastating neglected tropical infection of the subcutaneous tissues. It is caused by fungal and bacterial pathogens recognized as eumycetoma and actinomycetoma, respectively. Mycetoma treatment involves diagnosing the causative microorganism as a prerequisite to prescribing a proper medication. Current therapy of fungal eumycetoma causative agents, such as Madurella mycetomatis, consists of long-term antifungal medication with itraconazole followed by surgery, yet with usually unsatisfactory clinical outcomes. Actinomycetoma, on the contrary, usually responds to treatment with co-trimoxazole and amikacin. Therefore, there is a pressing need to discover novel broad-spectrum antimicrobial agents to circumvent the time-consuming and costly diagnosis. Using the resazurin assay, a series of 23 naphthylisoquinoline (NIQ) alkaloids and related naphthoquinones were subjected to in vitro screening against two fungal strains of M. mycetomatis and three bacterial strains of Actinomadura madurae and A. syzygii. Seven NIQs, mostly dimers, showed promising in vitro activities against at least one strain of the mycetoma-causative pathogens, while the naphthoquinones did not show any activity. A synthetic NIQ dimer, 8,8'''-O,O-dimethylmichellamine A (18), inhibited all tested fungal and bacterial strains (IC50 = 2.81-12.07 µg/mL). One of the dimeric NIQs, michellamine B (14), inhibited a strain of M. mycetomatis and significantly enhanced the survival rate of Galleria mellonella larvae infected with M. mycetomatis at concentrations of 1 and 4 µg/mL, without being toxic to the uninfected larvae. As a result, broad-spectrum dimeric NIQs like 14 and 18 with antimicrobial activity are considered hit compounds that could be worth further optimization to develop novel lead antimycetomal agents.

Integrated metabolomic and transcriptomic analysis reveals the regulatory mechanisms of flavonoid and alkaloid biosynthesis in the new and old leaves of Murraya tetramera Huang.

BACKGROUND: Murraya tetramera Huang is a traditional Chinese woody medicine. Its leaves contain flavonoids, alkaloids, and other active compounds, which have anti-inflammatory and analgesic effects, as well as hypoglycemic and lipid-lowering effects, and anti-tumor effects. There are significant differences in the content of flavonoids and alkaloids in leaves during different growth cycles, but the synthesis mechanism is still unclear. RESULTS: In April 2021, new leaves (one month old) and old leaves (one and a half years old) of M. tetramera were used as experimental materials to systematically analyze the changes in differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) with transcriptomics and metabolomics technology. This was done to identify the signaling pathways of flavonoid and alkaloid synthesis. The results showed that the contents of total alkaloids and flavonoids in old leaves were significantly higher than those in new leaves. Thirteen flavonoid compounds, three isoflavone compounds, and nineteen alkaloid compounds were identified, and 125 and 48 DEGs related to flavonoid and alkaloid synthesis were found, respectively. By constructing the KEGG (Kyoto Encyclopedia of Genes and Genomes) network of DEGs and DAMs, it was shown that the molecular mechanism of flavonoid biosynthesis in M. tetramera mainly focuses on the "flavonoid biosynthetic pathway" and the "flavonoid and flavonol biosynthetic pathway". Among them, p-Coumaryl alcohol, Sinapyl alcohol, Phloretin, and Isoquercitrin were significantly accumulated in old leaves, the up-regulated expression of CCR (cinnamoyl-CoA reductase) might promote the accumulation of p-Coumaryl alcohol, upregulation of F5H (ferulate-5-hydroxylase) might promote Sinapyl alcohol accumulation. Alkaloids, including indole alkaloids, pyridine alkaloids, imidazole alkaloids, and quinoline alkaloids, were significantly accumulated in old leaves, and a total of 29 genes were associated with these substances. CONCLUSIONS: These data are helpful to better understand the biosynthesis of flavonoids and alkaloids in M. tetramera and provide a scientific basis for the development of medicinal components in M. tetramera.

Exogenous regulation of macronutrients promotes the accumulation of alkaloid yield in anisodus tanguticus (Maxim.) pascher.

BACKGROUND: Anisodus tanguticus (Maxim.) Pascher (A. tanguticus) is a valuable botanical for extracting tropane alkaloids, which are widely used in the pharmaceutical industry. Implementing appropriate cultivation methods can improve both the quality and yield of A. tanguticus. A two-year field experiment was conducted from 2021 to 2023 using a single-factor randomized complete block design replicated three times. The study examined the effects of different nutrient levels (nitrogen: 0, 75, 150, 225, 300, 375 kg/ha; phosphorus: 0, 600, 750, 900, 1050, 1200 kg/ha; potassium: 0, 75, 112.5, 150, 187.5, 225 kg/ha) on the growth, primary alkaloid contents, and alkaloid yield of A. tanguticus at different growth stages (S-Greening, S-Growing, S-Wilting; T-Greening, T-Growing, and T-Wilting) in both the roots and aboveground portions. RESULTS: Our results demonstrate that nutrient levels significantly affect the growth and alkaloid accumulation in A. tanguticus. High nitrogen levels (375 kg/ha) notably increased both root and aboveground biomass, while phosphorus had a minimal effect, especially on aboveground biomass. For alkaloid content (scopolamine, anisodamine, anisodine, atropine), a moderate nitrogen level (225 kg/ha) was most effective, followed by low potassium (75 kg/ha), with phosphorus showing a limited impact. Increased phosphorus levels led to a decrease in scopolamine content. During the T-Growing period, moderate nitrogen addition (225 kg/ha) yielded the highest alkaloid levels per unit area (205.79 kg/ha). In the T-Wilting period, low potassium (75 kg/ha) and low phosphorus (750 kg/ha) resulted in alkaloid levels of 146.91 kg/ha and 142.18 kg/ha, respectively. This indicates nitrogen has the most substantial effect on alkaloid accumulation, followed by potassium and phosphorus. The Douglas production function analysis suggests focusing on root biomass and the accumulation of scopolamine and atropine in roots to maximize alkaloid yield in A. tanguticus cultivation. CONCLUSIONS: Our findings show that the optimum harvesting period for A. tanguticus is the T-Wilting period, and that the optimal nitrogen addition is 225 kg/ha, the optimal potassium addition is 75 kg/ha, and the optimal phosphorus addition is 600 kg/ha or less.

Variation of terpene alkaloids in Daphniphyllum macropodum across plants and tissues.

Daphniphyllum macropodum produces alkaloids that are structurally complex with polycyclic, stereochemically rich carbon skeletons. Understanding how these compounds are formed by the plant may enable exploration of their biological function and bioactivities. We employed multiple metabolomics techniques, including a workflow to annotate compounds in the absence of standards, to compare alkaloid content across plants and tissues. Different alkaloid structural types were found to have distinct distributions between genotypes, between tissues and within tissues. Alkaloid structural types also showed different isotope labelling enrichments that matched their biosynthetic relationships. The work suggests that mevalonate derived 30-carbon alkaloids are formed in the phloem region before their conversion to 22-carbon alkaloids which accumulate in the epidermis. This sets the stage for further investigation into the biosynthetic pathway.

Interplay between Amaryllidaceae alkaloids, the bacteriome and phytopathogens in Lycoris radiata.

Alkaloids are a large group of plant secondary metabolites with various structures and activities. It is important to understand their functions in the interplay between plants and the beneficial and pathogenic microbiota. Amaryllidaceae alkaloids (AAs) are unique secondary metabolites in Amaryllidaceae plants. Here, we studied the interplay between AAs and the bacteriome in Lycoris radiata, a traditional Chinese medicinal plant containing high amounts of AAs. The relationship between AAs and bacterial composition in different tissues of L. radiata was studied. In vitro experiments revealed that AAs have varying levels of antimicrobial activity against endophytic bacteria and pathogenic fungi, indicating the importance of AA synthesis in maintaining a balance between plants and beneficial/pathogenic microbiota. Using bacterial synthetic communities with different compositions, we observed a positive feedback loop between bacteria insensitive to AAs and their ability to increase accumulation of AAs in L. radiata, especially in leaves. This may allow insensitive bacteria to outcompete sensitive ones for plant resources. Moreover, the accumulation of AAs enhanced by insensitive bacteria could benefit plants when challenged with fungal pathogens. This study highlights the functions of alkaloids in plant-microbe interactions, opening new avenues for designing plant microbiomes that could contribute to sustainable agriculture.

The growth promotion in endophyte symbiotic plants does not penalise the resistance to herbivores and bacterial microbiota.

A trade-off between growth and defence against biotic stresses is common in plants. Fungal endophytes of the genus Epichloë may relieve this trade-off in their host grasses since they can simultaneously induce plant growth and produce antiherbivore alkaloids that circumvent the need for host defence. The Epichloë ability to decouple the growth-defence trade-off was evaluated by subjecting ryegrass with and without Epichloë endophytes to an exogenous treatment with gibberellin (GA) followed by a challenge with Rhopalosiphum padi aphids. In agreement with the endophyte-mediated trade-off decoupling hypothesis, the GA-derived promotion of plant growth increased the susceptibility to aphids in endophyte-free plants but did not affect the insect resistance in endophyte-symbiotic plants. In line with the unaltered insect resistance, the GA treatment did not reduce the concentration of Epichloë-derived alkaloids. The Epichloë mycelial biomass was transiently increased by the GA treatment but at the expense of hyphal integrity. The response of the phyllosphere bacterial microbiota to both GA treatment and Epichloë was also evaluated. Only Epichloë, and not the GA treatment, altered the composition of the phyllosphere microbiota and the abundance of certain bacterial taxa. Our findings clearly demonstrate that Epichloë does indeed relieve the plant growth-defence trade-off.

Navigating Amaryllidaceae Alkaloids: Bridging Gaps and Charting Biosynthetic Territories - A Comprehensive Review.

Amaryllidaceae alkaloid (AAs) biosynthesis has garnered significant attention in recent years, particularly with the commercialisation of galanthamine as a treatment for the symptoms of Alzheimer's disease. A significant amount of research work over the last 8 decades has focused on the understanding of AA biosynthesis, starting from early radiolabelling studies to recent multi-omics analysis with modern biotechnological advancements. Those studies enabled the identification of hundreds of metabolites, the characterisation of biochemical pathway, an understanding of the environmental stimuli, and of the molecular regulation of these pharmaceutically and agriculturally important metabolites. Despite the numerous works there remain significant gaps in understanding their biosynthesis in Amaryllidaceae plants. As such, further research is needed to fully elucidate the metabolic pathway and facilitate their production. This review aims to provide a comprehensive overall summary of the current state of knowledge on AAs biosynthesis, from elicitation of transcription factors expression in the cell nucleus to alkaloid transport in the apoplast, and to highlight the challenges that need to be overcome for further advancement.

The leaf idioblastome of the medicinal plant Catharanthus roseus is associated with stress resistance and alkaloid metabolism.

Catharanthus roseus leaves produce a range of monoterpenoid indole alkaloids (MIAs) that include low levels of the anticancer drugs vinblastine and vincristine. The MIA pathway displays a complex architecture spanning different subcellular and cell type localizations, and is under complex regulation. As a result, the development of strategies to increase the levels of the anticancer MIAs has remained elusive. The pathway involves mesophyll specialized idioblasts where the late unsolved biosynthetic steps are thought to occur. Here, protoplasts of C. roseus leaf idioblasts were isolated by fluorescence-activated cell sorting, and their differential alkaloid and transcriptomic profiles were characterized. This involved the assembly of an improved C. roseus transcriptome from short- and long-read data, IDIO+. It was observed that C. roseus mesophyll idioblasts possess a distinctive transcriptomic profile associated with protection against biotic and abiotic stresses, and indicative that this cell type is a carbon sink, in contrast to surrounding mesophyll cells. Moreover, it is shown that idioblasts are a hotspot of alkaloid accumulation, suggesting that their transcriptome may hold the key to the in-depth understanding of the MIA pathway and the success of strategies leading to higher levels of the anticancer drugs.

Total Synthesis of Ervaoffine J and K.

Herein, we describe the total synthesis of ervaoffine J & K from a central intermediate. Ervaoffine J was synthesized in eight steps in 14 % yield. Our strategy features an aerobic Winterfeldt oxidation to introduce the 4-quinolone moiety. Ervaoffine K was produced in ten steps and 10 % yield. The synthesis leveraged (bromodifluoromethyl)-trimethylsilane to induce a regioselective von Braun-type C-N bond fragmentation. This C-N bond cleavage unveiled the tetrasubstituted all-syn cyclohexane core of ervaoffine K and enabled the completion of its synthesis.

Indole C5-Selective Bromination of Indolo[2,3-a]quinolizidine Alkaloids via In Situ-Generated Indoline Intermediate.

There are many indole alkaloids that contain diverse functional groups attached to the benzene ring on the indole core. Promising biological activities of these alkaloids have been reported. Herein, we report the indole C5-selective bromination of indolo[2,3-a]quinolizidine alkaloids by adding nearly equimolar amounts of Br3 ⋅ PyH and HCl in MeOH. The resulting reaction plausibly proceeds through an indoline intermediate by the nucleophilic addition of MeOH to the C3-brominated indolenine intermediate. Data support the intermediacy of a C3-, C5-dibrominated indolenine intermediate as a brominating agent. These conditions demonstrate excellent selectivity for indole C5 bromination of natural products and their derivatives. Thus, these simple, mild, and metal-free conditions allow for selective, late-stage bromination followed by further chemical modifications. The utility of the brominated product prepared from naturally occurring yohimbine was demonstrated through various derivatizations, including a bioinspired heterodimerization reaction.

Modular Divergent Synthesis of Indole Alkaloid Derivatives by an Atypical Ugi Multicomponent Reaction.

We present an Ugi multicomponent approach to explore the chemical space around Aspidosperma-type monoterpene indole alkaloids. By variation of the isocyanide and carboxylic acid inputs we demonstrate the rapid generation of molecular diversity and the possibility to introduce handles for further modification. The key Ugi three-component reaction showed full diastereoselectivity towards the cis-fused ring system, which can be rationalized by DFT calculations that moreover indicate that the reaction proceeds via a Passerini-type hydrogen bonding mechanism. Several post-Ugi modifications were also performed, including Pictet-Spengler cyclization to highly complex nonacyclic natural product hybrid scaffolds.

Discovery of Unusual Ajmaline-Macroline Type Bisindole Alkaloids from Alstonia macrophylla by Building Blocks-Based Molecular Networking.

Three unusual ajmaline-macroline type bisindole alkaloids, alsmaphylines A-C, together with their postulated biogenetic precursors, were isolated from the stem barks and leaves of Alstonia macrophylla via the building blocks-based molecular network (BBMN) strategy. Alsmaphyline A represents a rare ajmaline-macroline type bisindole alkaloid with an S-shape polycyclic ring system. Alsmaphylines B and C are two novel ajmaline-macroline type bisindole alkaloids with N-1-C-21' linkages, and the former possesses an unconventional stacked conformation due to the presence of intramolecular noncovalent interactions. The chemical structures including absolute configurations of alsmaphylines A-C were established by comprehensive spectroscopic analyses, electronic circular dichroism (ECD) calculations, and single-crystal X-ray crystallography. In addition, a plausible biosynthetic pathway of these bisindole alkaloids as well as their ability to promote the protein synthesis on HT22 cells were discussed.