Denigrins and Dactylpyrroles, Arylpyrrole Alkaloids from a Dactylia sp. Marine Sponge

Molluscicide screening and identification of novel targets against Pomacea canaliculata

BACKGROUND

Owing to the nonavailability of any clear targets for molluscicides against Pomacea canaliculata, target-based screening strategy cannot be employed. In this study, the molluscicidal effects of typical pesticides on P. canaliculata were evaluated to obtain the molluscicide target. A series of arylpyrrole compounds were synthesized based on the discovered target, and their structure-activity relationships explored. A preliminary strategy for screening molluscicides based on specific targets was also developed.

RESULTS

A laboratory colony of P. canaliculata was developed, which showed no difference in sensitivity to niclosamide compared with the wild group, while exhibiting a higher stability against pesticide response. Mitochondrial adenosine triphosphate (ATP) synthase inhibitors and mitochondrial membrane potential uncouplers were identified and validated as potential targets for molluscicide screening against P. canaliculata. A series of arylpyrrole compounds were designed and synthesized. The median lethal concentration of 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile (Compound 102) was 10-fold lower than that of niclosamide.

CONCLUSION

New molluscicide targets were discovered and validated, and preliminary strategies were explored for pesticide screening based on these targets. Compound 102 exhibited a high molluscicidal activity and had a great potential value for exploring a molluscicide to control P. canaliculata. © 2024 Society of Chemical Industry.

Electrochemical Sulfonylation/Cyclization of N-Alkenylacrylamides with Sodium Sulfinates or Sulfonyl Hydrazides

Two general protocols for the regioselective electrochemically enabled sulfonylation cyclization of N-alkenylacrylamides with sodium sulfinates or sulfonyl hydrazides were described. These methods were carried out under mild, chemical oxidant-free, and transition-metal-free conditions with a broad substrate scope and good functional group tolerance to provide sulfonyl-containing 4-pyrrolin-2-ones, which is readily scalable to the gram scale.

Total Syntheses of the Structures Assigned to Denigrins A, B, C, F, and G, 3,4-Diaryl-Pyrrole and -Pyrrolidinone Alkaloids, and the Conversion of Congener B into the Co-metabolite Spirodactylone

The title marine natural products have been prepared by total synthesis and in the case of congeners 3, 6, and 7 for the first time. Each of these was obtained by manipulation of readily prepared denigrin B (2). The structure, 3, assigned to denigrin C is shown to be incorrect. Reaction of compound 2 with DDQ has led, in high yield, to the related natural product spirodactylone (16), while treating the corresponding permethyl ether 15 with PIFA/BF3·Et2O provides compound 20, embodying an isomeric framework.

Electrophotocatalysis Versus Indirect Electrolysis: Electrochemical Selenocyclization of 3-Aza-1,5-dienes Facilitated by Energy Transfer, Direct Photolysis or N-Hydroxyphthalimide

Three hybrid electrochemical protocols, which involve the energy transfer, direct photolysis and N-hydroxyphthalimide catalyst, respectively, are presented for the selenylation/cyclization of the fragile substrates of 3-aza-1,5-dienes with diorganyl diselenides to afford 3-selenomethyl-4-pyrrolin-2-ones. The two electrophotocatalytic reactions and the indirect electrolysis one are both regioselective and external-oxidant- and transition-metal-free, and are associated with a broad substrate scope and high Se-economy, and all three methods are amenable to gram-scale syntheses, late-stage functionalizations, sunlight-induced experiments and all-solar-driven syntheses.

Denigrins H-L: Sulfated Derivatives of Denigrins D and E from a New Zealand Dictyodendrilla c.f. dendyi Marine Sponge

Five new sulfated arylpyrrole and arylpyrrolone alkaloids, denigrins H-L (1-5), along with two known compounds, dictyodendrin B and denigrin G, were isolated from an extract of a New Zealand Dictyodendrilla c.f. dendyi marine sponge. Denigrins H-L represent the first examples of sulfated denigrins, with denigrins H and I (1-2), as derivatives of denigrin D, containing a pyrrolone core, and denigrins J-L (3-5), as derivatives of denigrin E (6), containing a pyrrole core. Their structures were elucidated by interpretation of 1D and 2D NMR spectroscopic data, ESI, and HR-ESI-MS spectrometric data, as well as comparison with literature data. Compounds 1-5, along with six known compounds previously isolated from the same extract, showed minimal cytotoxicity against the HeLa cervical cancer cell line.

Investigation of the Dietary Preferences of Two Dorid Nudibranchs by Feeding-Choice Experiments and Chemical Analysis

Feeding-choice experiments were conducted under laboratory conditions with two dorid spongivorous nudibranchs, Goniobranchus aureomarginatus and Ceratosoma amoenum, collected from a sponge meadow off Tauranga, New Zealand with two sponge prey (Dysidea teawanui sp.nov. and an undescribed species from the Dictyodendrillidae family, possibly Dictyodendrilla tenella (Lendenfeld 1888). The first choice of prey, the total number of prey choices made, and the time spent on each prey target was recorded, results indicating that each nudibranch had strong preferences for specific prey species. Preferences were significant when the time spent grazing on prey was taken into consideration. Goniobranchus aureomarginatus had a strong preference for the undescribed Dictyodendrillid sponge, while Ceratosoma ameonum preferred Dysidea teawanui. The results of the feeding-choice experiments matched observations in the wild. Chemical analysis of the undescribed Dictyodendrillid sponge led to the isolation and characterisation of six known bioactive metabolites, dictyodendrin C (1), D (2) and F (3), as well as denigrin E (4), dactylpyrrole A (5) and lamellarin O1 (6). Two of the known compounds, dictyodendrins C (1) and F (3) were also isolated from G. aureomarginatus individuals. Chemical analysis of D. teawanui afforded ergosterol peroxide, 5α,8α-epidioxy-24-methylcholesta-6,22-dien-3β-ol (7). The structures of the isolated natural products were elucidated based on extensive analysis of 1D and 2D NMR data.

Electrochemical or Photoelectrochemical Alkenylpolyfluoroalkylation of 3-Aza-1,5-dienes: Regioselective Entry to Polyfluoroalkylated 4-Pyrrolin-2-ones

An electrochemical or photoelectrochemical regioselective polyfluoroalkylation/cyclization cascade of 3-aza-1,5-dienes with sodium fluoroalkanesulfinates is presented. This protocol proceeds with a broad substrate scope and good functional group tolerance under mild, oxidant-free, transition-metal-free, and electrolyte-free conditions to provide 3-polyfluoroalkylated 4-pyrrolin-2-ones in one step from readily available N-vinylacrylamides, and it is readily scalable to the Gram scale.

Catalytic asymmetric de novo construction of 4-pyrrolin-2-ones via intermolecular formal [3+2] cycloaddition of azoalkenes with azlactones

The chiral phosphoric acid-catalyzed asymmetric intermolecular formal [3+2] cycloaddition of azoalkenes with azlactones has been established. This convergent protocol leads to a facile and enantioselective de novo construction of a wide range of fully substituted 4-pyrrolin-2-ones bearing a fully substituted carbon atom in good yields and with excellent enantioselectivities (26 examples, 72-95% yields and 87-99% ee).

Total Synthesis of Denigrin E and Its Oxidative Conversion into Co-occurring Metabolite Denigrin D

An unambiguous, six-step total synthesis of denigrin E (5) from anisaldehyde 22 has been achieved, confirming the structure of this marine natural product. On treatment with t-BuOOH/Mo(CO)₆, compound 5 undergoes a unique and possibly biogenetically relevant oxidative rearrangement to generate the co-occurring metabolite denigrin D (4), which is obtained in 61% yield.

Insights into the κ-P,N Coordination of 1,3,5-Triaza-7-phosphaadamantane and Derivatives: κ-P,N-Heterometallic Complexes and a 15N Nuclear Magnetic Resonance Survey

Complexes {[(PTA)₂CpRu-μ-CN-1κC:2κ²N-RuCp(PTA)₂-ZnCl₃]}·2DMSO (13) {[ZnCl₂(H₂O)]-(PTA-1κP:2κ²N)(PTA)CpRu-μ-CN-1κC:2κ²N-RuCp(PTA)(PTA-1κP:2κ²N)-[ZnCl₂(H₂O)]}Cl (14), [RuCp(HdmoPTA)(PPh₃)(PTA)](CF₃SO₃)₂ (20), [RuCp(HdmoPTA)(HPTA)(PPh₃)](CF₃SO₃)₃ (21), and [RuCp(dmoPTA)(PPh₃)(PTA)](CF₃SO₃) (22) were obtained and characterized, and their crystal structure together with that of the previously published complex 18 is reported. The behavior of the 1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]decane (PTA) and 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (dmoPTA) ligands against protonation and κN-coordination is discussed, on the basis of ¹⁵N nuclear magnetic resonance data collected on 22 different compounds, including PTA (1), HdmoPTA (7H), and some common derivatives as free ligands (2–6 and 8), along with mono- and polymetallic complexes containing PTA and/or HdmoPTA (9–22). ¹⁵N detection via ¹H–¹⁵N heteronuclear multiple bond correlation allowed the construction of a small library of ¹⁵N chemical shifts that shed light on important features regarding κN-coordination in PTA and its derivatives.

To shed light on the behavior of the triazaphosphines 1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]decane (PTA) and 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (dmoPTA) upon κN coordination and N protonation, the ¹⁵N chemical shifts of 22 compounds, including PTA and a representative variety of its derivatives, piano-stool complexes, were collected by ¹H−¹⁵N heteronuclear multiple bond correlation nuclear magnetic resonance. New heterometallic complexes containing PTA were also synthesized and fully characterized.

Marine natural products

Covering: 2020This review covers the literature published in 2020 for marine natural products (MNPs), with 757 citations (747 for the period January to December 2020) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1407 in 420 papers for 2020), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. A meta analysis of bioactivity data relating to new MNPs reported over the last five years is also presented.

Exploring the regioselectivity of the cyanoalkylation of 3-aza-1,5-dienes: photoinduced synthesis of 3-cyanoalkyl-4-pyrrolin-2-ones

Regioselective cyanoalkylalkenylation of 3-aza-1,5-dienes with oxime esters induced by visible light.

Marine Pyrrole Alkaloids

Nitrogen heterocycles are essential parts of the chemical machinery of life and often reveal intriguing structures. They are not only widespread in terrestrial habitats but can also frequently be found as natural products in the marine environment. This review highlights the important class of marine pyrrole alkaloids, well-known for their diverse biological activities. A broad overview of the marine pyrrole alkaloids with a focus on their isolation, biological activities, chemical synthesis, and derivatization covering the decade from 2010 to 2020 is provided. With relevant structural subclasses categorized, this review shall provide a clear and timely synopsis of this area.

The 2021 Winners of the Lifetime Achievement and Emerging Leader in Chromatography Awards

Paul Haddad and Erik L. Regalado are the winners of the 14th annual LCGC Lifetime Achievement and Emerging Leader in Chromatography Awards, respectively. We review their achievements.