Stachyodin A,a pterocarpan derivative with unusual spirotetrahydrofuran ring from the roots of Indigofera stachyodes

Stachyodin A (1), a rearrangement product of pterocarpan featuring a 6/5/5/6 tetracyclic ring system with an unusual spirotetrahydrofuran ring, and stachyodin B (2), a new dihydrochalcone, along with five known analogues (3–7) were isolated from the roots of Indigofera stachyodes. The structures of 1 and 2 were elucidated on the basis of their HRESIMS and NMR spectroscopic data, and their absolute configurations were determined by X-ray crystallographic analysis and electronic circular dichroism (ECD) data, respectively. Compounds 2–4 showed inhibition of nitric oxide production in lipopolysaccharide-activated BV-2 microglial cells.     

Norcrocrassinone: A novel tetranorditerpenoid possessing a 6/6/5 fused ring system from Croton crassifolius

Norcrocrassinone (1), a novel tetranorditerpenoid possessing a fused 6/6/5 ring system, was isolated from the roots of Croton crassifolius. The structure of 1 was elucidated by extensive spectroscopic methods and confirmed by single crystal X-ray diffraction. The anti-Alzheimer’s disease (AD) activity of 1 was evaluated using humanized Caenorhabditis elegans AD pathological model.     

Angustifolinoid A,a macrocyclic flavonoid glycoside from Elaeagnus angustifolia flowers

A novel macrocyclic flavonoid glycoside, angustifolinoid A (1), featuring an unprecedented 13-membered heterocyclic ring moiety, along with a known flavonoid glycoside, tiliroside (2), were isolated from Elaeagnus angustifolia flowers. Their structures were determined by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation. Biosynthesis analysis indicated that compound 1 might be derived from compound 2 via a key enzymatic intramolecular oxidative coupling. Compounds 1 and 2 showed inhibitory activities against cyclooxygenases, COX-1 and COX-2.     

Fusopoltide A and fusosterede A,A polyketide with a pentaleno[1,2-c]pyran ring system and A degraded steride,from the fungus Fusarium solani

Fusopoltide A (1), a novel polyketide featured a pentaleno[1,2-c]pyran ring, and fusosteride A (2), a new steride with A/B-ring degraded, together with a known ergosterol peroxide (3), were isolated from a solid culture extract of Fusarium solani. The structures of 1 and 2 were elucidated by detailed interpretation of their HRESIMS and NMR spectroscopic data and their absolute configurations were determined by X-ray crystallographic analysis and the electronic circular dichroic (ECD) method, respectively. The postulated biogenetic pathways of 1 and 2 were also discussed. Compound 1 exhibits inhibitory activity against cyclooxygenase-2 (COX-2) with an IC₅₀ value of 3.45?μM.     

Seconoriridone A: A C16-seco-noriridal derivative with a 5/5/7 tricyclic skeleton from Belamcanda chinensis

Seconoriridone A (1), a novel C₁₆-seco-noriridal with a 5/5/7 tricyclic scaffold, was isolated from the rhizome of Belamcanda chinensis. Its structure and absolute configuration were determined by NMR spectroscopy and quantum chemical calculations. Notably, seconoriridone A featured a 2-butanonyl moiety with oxidative cleavage of the conventionally multisubstituted cyclohexane ring of iridals. Seconoriridone A was a mixture of C-14 epimers in the presence of hemiacetal. The plausible biosynthetic pathway for 1 was deduced.     

Lycogladines A-H,fawcettimine-type Lycopodium alkaloids from Lycopodium complanatum var. glaucum Ching

Five new fawcettimine-type alkaloids (1–5) and three new natural products (6–8), along with four known analogues, fawcettimine (9), fewcettidine (10), lycopoclavamine B (11), and lycopladine B (12), were isolated from the whole plant of Lycopodium complanatum var. glaucum Ching. The structures of lycogladines A-H (1–8) were determined based on HRESIMS, 1D and 2D NMR spectroscopic analysis, as well as single-crystal X-ray diffraction. Compound 1 possesses a new ring system that is formed through the linkage of C-13-OC-2, which is rarely present in Lycopodium alkaloids (LAs). Compounds 1–8 were tested for their β-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) and acetylcholinesterase (AChE) inhibitory activities.     

Poecillastrin E,F, and G,cytotoxic chondropsin-type macrolides from a marine sponge Poecillastra sp.

Poecillastrin E (1), F (2), and G (3) were isolated from a marine sponge Poecillastra sp. as the cytotoxic constituents. Their planar structures were determined by analyzing the MS and NMR spectra. They are closely related to the known poecillastrin C (4). The absolute configuration of the β-hydroxyaspartic acid (OHAsp) residue was determined to be D-threo by Marfey's analysis of the hydrolysate. The mode of lactone ring formation of OHAsp residue in 1–3 was determined by selective reduction of the ester linkage followed by acid hydrolysis.     

Trichilin B, a novel limonoid with highly rearranged ring system from Trichilia connaroides

Trichilin B (2), a limonoid having an unprecedented highly rearranged ring system, along with biosynthetically correlated trichilin A (1), was isolated from Trichilia connaroides. The structures were elucidated by spectroscopic analysis. Compound 2 features a unique 9,17-oxygen bridge, while two unprecedented δ-lactone rings fused to rings A and B at C-5, C-9 and ring C at C-8, C-14. Their cytotoxic activities were also evaluated.     

Dictyoneolone,a B/C ring juncture-defused steroid from a Dictyonella sp. sponge

Dictyoneolone (1), a new secosteroid was isolated from a Dictyonella sp. sponge collected from Gageo-do, Korea. Based upon the results of combined spectroscopic analyses, the structure of this compound was determined to possess a highly unusual B/C ring juncture-defused moiety. The configurations of 1 were determined by a combination of proton-proton couplings and NOESY analyses. Dictyoneolone exhibited weak cytotoxicity against the K562 and A549 cancer cell lines.     

Senepodines B-E, new C22N2 alkaloids from Lycopodium chinense

Four new C₂₂N₂Lycopodium alkaloids, senepodines B-E (2-5), consisting of an octahydroquinoline ring and a quinolizidine ring have been isolated together with senepodine A (1) from the club moss Lycopodium chinense. The relative and absolute stereochemistry of 2-5 were determined by combination of NOESY correlations and chemical transformation, while the absolute configuration of 1 was assigned by exciton chirality method.     

Formosalides A and B, cytotoxic 17-membered ring macrolides from a marine dinoflagellate Prorocentrum sp.

Formosalides A (1) and B (2), two novel cytotoxic 17-membered ring macrolides with all-cis tetraenes, a tetrahydropyran ring, and a tetrahydrofuran ring, were isolated from the cultured marine dinoflagellate Prorocentrum sp. Their gross structures, including local relative stereostructures, were elucidated by extensive spectroscopic studies.     

Lycopladine H, a novel alkaloid with fused-tetracyclic skeleton from Lycopodium complanatum

A novel Lycopodium alkaloid, lycopladine H (1), with a fused-tetracyclic ring system consisting of an azocane ring connected to a [2,2,2]-bicyclooctane ring and a 3-piperidone ring, was isolated from the club moss Lycopodium complanatum. The structure and relative stereochemistry of 1 were elucidated on the basis of spectroscopic data.     

PMR investigation into the structure of some n-substituted 1-amino-1-deoxy-D-fructoses (amadori rearrangement products) : Evidence for a preferential conformation in solution

The PMR spectra at 220 MHz of some Amadori rearrangement products deduced from D-glucose with p-toluidine (1), N-methylphenylamine (2), di-butylamine (4), piperdine (5), and morpholine (6) have been studied in detail.Compounds 1-6 appear to exist in solution predominantly as an equilibrium mixture of the furanose and pyranose ring. The pyranose ring occurs exclusively in the β(D)-²C₅-conformation (corresponds to Reeves 1C-conformation). The furanose ring probably exists as a mixture of both the β- and α-anomer, in which the β-anomer is favoured.     

Celogentin K, a new cyclic peptide from the seeds of Celosia argentea and X-ray structure of moroidin

A new cyclic peptide with a 3-hydroxyoxindole ring, celogentin K (1), has been isolated from the seeds of Celosia argentea and the structure including its absolute stereochemistry was assigned by using extensive NMR, MS/MS, and CD spectra. The stereostructure of a known related bicyclic peptide, moroidin (2), was confirmed by a single crystal X-ray diffraction analysis.     

Rhodauricanol A,an analgesic diterpenoid with an unprecedented 5/6/5/7 tetracyclic system featuring a unique 16-oxa-tetracyclo[11.2.1.01,5.07,13]hexadecane core from Rhododendron dauricum

A novel diterpenoid with an unprecedented 5/6/5/7 tetracyclic system, rhodauricanol A (1), five new grayanane-derived diterpenoids, dauricanols A?E (2?6), and five known ones (7?11) were isolated from the flowers of Rhododendron dauricum. Rhodauricanol A (1) possesses a unique 5/6/5/7 tetracyclic ring system featuring a 16-oxa-tetracyclo[11.2.1.0^1,5.0^7,13]hexadecane core. Dauricanols A?C (2?4) are the first 1,3-dioxolane conjugates of grayanane diterpenoids and 5-hydroxymethylfurfural and vanillin, respectively, and dauricanols D (5) and E (6) represent the first examples of 6-deoxy-1,5-seco-grayanane diterpenoids. Their structures were determined by spectroscopic methods, quantum chemical calculation including ¹³C NMR-DP4+ analysis and ECD calculation, and single-crystal X-ray diffraction analysis. Plausible biosynthetic pathways for 1?4 were proposed. All the isolates showed significant analgesic activities, and dauricanols B (3) and C (4) showed more potent analgesic activities than the positive control, morphine.     

Kiamycins B and C,unusual bridged angucyclinones from a marine sediment-derived Streptomyces sp.

Kiamycins B (1) and C (2), two unusual angucyclinones bearing a novel 6,12-epoxybenz[a]anthracene ring system, were isolated from the cultures of a marine sediment-derived Streptomyces sp. along with one structurally related derivative 3. Their structures and stereochemistries were determined by spectroscopic analyses, single-crystal X-ray diffraction and electronic circular dichroism (ECD) calculations.     

Zamamidine C, 3,4-dihydro-6-hydroxy-10,11-epoxymanzamine A, and 3,4-dihydromanzamine J N-oxide, new manzamine alkaloids from sponge Amphimedon sp.

New manzamine alkaloids, zamamidine C (1), 3,4-dihydro-6-hydroxy-10,11-epoxymanzamine A (2), and 3,4-dihydromanzamine J N-oxide (3), have been isolated from an Okinawan marine sponge Amphimedon species. The structures and stereochemistries of 1-3 were elucidated from the spectroscopic data and chemical derivatization. Zamamidine C (1) is a new manzamine alkaloid possessing a second β-carboline ring via an ethylene unit at N-2 of manzamine D, while 3,4-dihydro-6-hydroxy-10,11-epoxymanzamine A (2) is the first manzamine alkaloid possessing an epoxide ring at C-10 and C-11. Zamamidine C (1) showed significant antitrypanosomal activity against Trypanosoma brucei brucei, the parasite associated with sleeping sickness, and antimalarial activity against Plasmodium falciparum, the causative agent of malaria in vitro.     

Isolation and biological evaluation of chromone alkaloid dysoline,a new regioisomer of rohitukine from Dysoxylum binectariferum

The chromone alkaloid dysoline (1), a new regioisomer of rohitukine (2) along with rohitukine and rohitukine-N-oxide (3) were isolated from the stem barks of Dysoxylum binectariferum. The structure of dysoline (1) was determined by extensive 2D-NMR studies and the absolute configuration was established by NOESY and CD spectra. Dysoline (1) consisted of a 5,7-dihydroxy-2-methylchromone nucleus substituted with a 2′-hydroxylated N-Me piperidine ring at the C-6 position. Dysoline differs from rohitukine by the position of the piperidine ring on the chromone nucleus. Dysoline displayed promising cytotoxicity in HT1080 fibrosarcoma cells with an IC₅₀ of 0.21 μM, and also displayed significant inhibition of proinflammatory cytokines TNF-α and IL-6.     

Mufolinin A,an unprecedented ring A-seco 10-ethyllimonoid from Munronia unifoliolata

Mufolinin A(1), a ring A-seco rearranged limonoid with an unprecedented ethyl at C-10 and novel 6/6/6/5 fused-ring skeleton, together with three new potential precursors(ring A-seco limonoids, 2–4) were isolated from Munronia unifoliolata. Their structures and absolute configurations were confirmed by nuclear magnetic resonance(NMR), high resolution electrospray ionization mass spectroscopy(HRESIMS), X-ray crystallography, electronic circular dichroism(ECD) calculations and NMR calculations with...     

New polycyclic tetramate macrolactams from marine-derived Streptomyces sp. SCSIO 40060

Polycyclic tetramate macrolactams (PTMs) are widely distributed in nature and are generated from a compact biosynthetic pathway. Bioinformatics analysis of the draft genome sequence of marine-derived Streptomyces sp. SCSIO 40060 revealed the presence of a putative PTM-encoding biosynthetic gene cluster (BGC). Comparison of this PTM BGC with those from the databank by genome mining suggests that Streptomyces sp. SCSIO 40060 should produce PTMs with a 5/6/5 type of carbocyclic ring. Subsequently, a 40-L scale of cultivation of Streptomyces sp. SCSIO 40060 led to the isolation and characterization of four known PTMS, ikarugamycin (1), epoxyikarugamycin (2), capsimycin (3), capsimycin C (4), and three new PTMs, hydroxyikarugamycins A–C (5–7). The planar structures of 5–7 were assigned by comprehensive spectroscopic analysis and the absolute configurations of 5 and 6 were unequivocally determined by X-ray diffraction analysis. The absolute structure of 7 was deduced by comparing ECD spectra of 5–7. Capsimycin (3) showed antimicrobial activity against methicillin-resistant Staphylococcus aureus with a MIC value of 16?μg/mL and displayed cytotoxicity against several cancer cell lines with IC₅₀ values ranging from 2.62 to 6.87?μM.