Structure and absolute configuration of penicilliumine,a new alkaloid from Penicillium commune 366606

Penicilliumine (1), a new structure was isolated from the fermentation Penicillium commune 366606, a marine-derived fungus isolated from the sea water collected at Qingdao, China. HPLC chiral separation of 1 afforded two enantiomers (−)-penicilliumine and (+)-penicilliumine, respectively. The structure of 1 was established by comprehensive spectroscopic data, and single-crystal X-ray diffraction. The absolute configuration of enantiomers was determined by quantum mechanical computation of electronic circular dichroism (ECD).     

Novel tetranortriterpenoid derivatives from Munronia henryi

Six novel tetranortriterpenoid derivatives were isolated from the methanolic extract of the whole bodies of Munronia henryi, namely, munronins A-F (1-6). In compounds (3-6), the side chains are rare in tetranortriterpenoids. Their structures were established by extensive NMR experiments. Based on the diversity of the side chains, possible biodegradations for the side chains of compounds 1-6 from euphane or tirucallane skeleton are proposed. Munronins A-E exhibited moderate antifeeding activity against Pieris brassicae L, while munronin F showed negative activity.     

Chemoenzymatic resolution of epimeric cis 3-carboxycyclopentylglycine derivatives

Epimeric 3-carboxycyclopentylglycines (+)-10/(−)-10 and (+)-11/(−)-11 were efficiently prepared by the way of a sequence of Diels-Alder and retro-Claisen reactions. The synthesis incorporates a concise and inexpensive chemoenzymatic resolution of racemic compounds 4,5a, the N,O-protected derivatives of amino acids 10,11. Systematic screening with different enzymes and microorganisms was performed to select a very efficient catalyst for the separation of the racemic mixtures. The reaction conditions allowing deprotection of both ester and amino functions and to avoiding epimerization processes were studied. Enantiomers (i.e., (+)-10/(−)-10 and (+)-11/(−)-11) were obtained in high enantiopurity. The absolute configuration of all stereocenters was unequivocally assigned.     

Diverse prieurianin-type limonoid derivatives from the fruits of Aphanamixis grandifolia and their absolute configuration determination

Twenty-five new highly oxygenated prieurianin-type limonoids, zaphaprinins A–Y (1–25), were isolated from the fruits of Aphanamixis grandifolia. Their structures were elucidated by extensive spectroscopic analyses. Absolute configurations for the key structures like 1 were assigned by a comprehensive method, such as comparing the calculated electronic circular dichroism (ECD) with the experimental one, single-crystal X-ray and Mosher ester method were also involved for other compounds' study. The solid data from X-ray diffraction allowed revision of the stereochemistry of the C₁–C₁₄ tetrahydropyran ring-type limonoid. The insecticidal activities of all the limonoids were evaluated.     

Novel nardosinane type sesquiterpenoids from Nardostachys chinensis Batal

Five new sesquiterpenoids Nardosinanone A–E (1–5), were isolated from the extract of Nardostachys chinensis, and their structures were determined by extensive spectroscopic analysis. Compound 1 featured a nardosinane sesquiterpenoid with an unusual tricyclic skeleton. Compounds 2–4 were new nardosinane sesquiterpenoids bearing a rare 10,11-epoxy group. The absolute configurations were determined by single-crystal X-ray diffraction analysis, ECD calculation method, the CD analysis of the in situ formed [Rh₂(OCOCF₃)₄] complex, and the CD data analysis based on the octane rule of cyclohexanone.     

Novel polycyclic polyprenylated acylphloroglucinols from Hypericum sampsonii

Four new polycyclic polyprenylated acylphloroglucinols with a tricyclo[4.3.1.1^5,7]undecane skeleton, hypersampsones N–Q (1–4), together with four know compounds (5–8), were isolated from the aerial parts of Hypericum sampsonii. Compound 1 bearing a rare 20, 25-epoxy group with the losing of C-21–23 in isopentenyl. An unusual 21, 24-epoxy group was found in the structure of 2. All structures were elucidated by extensive NMR spectroscopic methods. The absolute configurations of new compounds were determined by ECD calculation.     

New iodotyramine derivatives from Didemnum rubeum

The study of an aqueous extract from the ascidian Didemnum rubeum permitted the isolation of a previously reported derivative diiodo-tyramine derivative together with six new iodo-tyramine derivatives. Their structures were elucidated by NMR and MS analysis.     

Indole alkaloids from cultivated Vinca major

Nine new indole alkaloids, vinmajines A–I (1–9), and 43 known indole alkaloids were isolated from cultivated Vinca major in Kunming. The new structures were elucidated by extensive spectroscopic and quantum theory analysis. In addition, the results also supported that types of indole alkaloids from V. major might be influenced significantly by the ecological environment.     

Prenyleudesmanes,rare natural diterpenoids from Dysoxylum densiflorum

Prenyleudesmanes are rare natural diterpenoids and their structural features need further characterization. In this paper, twelve new prenyleudesmanes, dysoxydenones A–L (1–12), together with one known prenyleudesmane were isolated from Dysoxylum densiflorum. This is the first time the absolute configurations of prenyleudesmanes have been unambiguously confirmed by single-crystal X-ray diffraction with Cu Kα radiation. Moreover, the absolute configuration of dysokusone D was revised.     

Absolute configuration and antibiotic activity of neosartorin from the endophytic fungus Aspergillus fumigatiaffinis

Neosartorin (1) was isolated from the endophytic fungus Aspergillus fumigatiaffinis. The absolute configuration of 1, including both axial and central chirality elements, was established as (aR,5S,10R,5′S,6′S,10′R) for the first time on the basis of its electronic circular dichroism (ECD) spectra aided with TDDFT–ECD calculations. Neosartorin (1) exhibited substantial antibacterial activity against a broad spectrum of Gram-positive bacterial species including staphylococci, streptococci, enterococci, and Bacillus subtilis with minimal inhibitory concentrations in the range of 4–32 μg/mL. When the toxicity of 1 against eukaryotic cells was measured using a panel of different cancer cell lines such as HELA and BALB/3T3, the average IC₅₀ values exceeded 32 μg/mL.     

Ten new calyxins from Alpinia katsumadai: a systematically studies on the stereochemistry of calyxins

Ten new calyxin natural products, named calyxin N (1), ent-calyxin N (2), calyxin O (3), ent-calyxin O (4), calyxin P (5), 9″-epicalyxin P (6), calyxin Q (7), calyxin R (8), calyxin S (9) and 5-epicalyxin S (10), were isolated from the seeds of Alpinia katsumadai. Their planar structures were elucidated by a combination of various spectroscopic methods, primarily NMR and MS, while the absolute configurations of the isolated calyxins were comprehensively studied by the modified Mosher's method, electronic circular dichroism (ECD) and theoretical calculations. This is the first systematically study on the absolute configurations of calyxins. Most of the isolated compounds showed moderate to strong antiproliferative activities against NCI-H460, HeLa, SMMC-7721 and HCT-116 cancer cell lines.     

Tabularisins A-D, phragmalin ortho esters with new skeleton isolated from the seeds of Chukrasia tabularis

Tabularisins A-D (1-4), a new class of phragmalins incorporating a cyclopropanyl ring, were isolated from Chukrasia tabularis. Compounds 1 and 2 are also the first examples of phragmalins with an 8,9,11-ortho ester. The structures of 1 and 3 were confirmed by single crystal X-ray studies. The absolute configuration of 2 was determined by CD exciton chirality method on its benzoate (2a), and those of 1, 3, and 4 were proposed by correlating with 2 chemically and biogenetically.     

Induced secondary metabolites from the endophytic fungus Aspergillus versicolor through bacterial co-culture and OSMAC approaches

Two new cryptic 3,4-dihydronaphthalen-(2H)-1-one (1-tetralone) derivatives, aspvanicin A (1) and its epimer aspvanicin B (2), as well as several known cryptic metabolites (3–8), were obtained from the ethyl acetate extract of the co-culture of the endophytic fungus Aspergillus versicolor KU258497 with the bacterium Bacillus subtilis 168 trpC2 on solid rice medium. When A. versicolor was cultured axenically in liquid Wickerham medium supplemented with 3.5% DMSO, an additional three known secondary metabolites (9–11) were isolated that were lacking when the fungus was fermented on rice medium. The structures of the new compounds were elucidated using one- and two-dimensional NMR spectroscopy as well as HRESIMS. The relative and absolute configurations of 1 and 2 were determined by the combination of NMR and electronic circular dichroism (ECD) analysis aided by DFT conformational analysis and TDDFT-ECD calculations. The ECD calculations revealed that although the sign of the blue-shifted overlapping n-π¹ ECD transition follows the helicity rule of cyclic aryl ketones, the calculation of low-energy conformers and ECD spectra was necessary to determine the stereochemistry. All metabolites were assessed for their antibacterial and cytotoxic activities; one of the new diastereomers, compound 2, showed moderate cytotoxic activity against the mouse lymphoma cell line L5178Y.     

3-Oxyanthranilic acid derivatives from Actinomadura sp. BCC27169

Eight new compounds including 9′-[2-amino-3-(4″-O-methyl-α-rhamnopyranosyloxy) phenyl]nonanoic acid (1), 9′-[2-amino-3-(4″-O-methyl-α-ribopyranosyloxy)phenyl] nonanoic acid (2), 11′-[2-amino-3-(4″-O-methyl-α-rhamnopyranosyloxy)phenyl]undecanoic acid (3), 11′-[2-amino-3-(4″-O-methyl-α-ribopyranosyloxy)phenyl]undecanoic acid (4), 8-(4′-O-methyl-α-rhamnopyranosyloxy)-3,4-dihydroquinolin-2(1H)-one (5), 8-(4′-O-methyl-α-ribopyranosyloxy)-3,4-dihydroquinolin-2(1H)-one (6), 8-(4′-O-methyl-α-rhamnopyranosyloxy)-2-methyquinoline (7), and 8-(4′-O-methyl-α-ribopyranosyloxy)-2-methylquinoline (8) were isolated from Actinomadura sp. BCC27169. The chemical structures of these compounds were determined based on NMR and high-resolution mass spectroscopy. The absolute configurations of these monosaccharides were revealed by the hydrolysis of compounds 7 and 8. Compounds 3 and 8 exhibited antitubercular activity at MIC 50 μg/mL. Only compound 3 showed cytotoxicity against KB cell at IC₅₀ 18.63 μg/mL, while other isolated compounds were inactive at tested maximum concentration (50 μg/mL).     

Structure determination and absolute configuration of cannabichromanone derivatives from high potency Cannabis sativa

Three new cannabichromanone derivatives were isolated from high potency cannabis, along with the known cannabichromanone. Full spectroscopic data, including the use of electronic circular dichroism and Mosher ester analysis to determine the absolute configuration of these compounds, are reported. All isolates were tested for antimicrobial, antimalarial, antileishmanial, and anti-oxidant activities.     

Highly efficient immobilization of Cinchona alkaloid derivatives to silica gel via click chemistry

Click chemistry was adapted to the immobilization of various Cinchona alkaloid derivatives bearing alkyne functionality onto azide-modified silica gel surfaces. The developed protocol employs very mild reaction conditions, with catalytic amounts of copper(I) iodide (1-5 mol %) in acetonitrile at room temperature, ensuring complete chemical integrity of the multi-functional ligands. The utility of this approach is demonstrated by the attachment of didehydroquinine tert-butylcarbamate to azido-grafted silica gel to produce an effective chiral stationary phase for HPLC enantiomer separation. A comparison of the chromatographic behavior of this click-immobilized phase with that of a commercially available thioether-linked chiral stationary phase revealed very similar performance characteristics for various model analytes. This observation suggests that the click-immobilization may offer an appealing alternative to the established silica gel-grafting technologies, allowing for the specific benefits of high and readily controllable loading levels under noninvasive conditions.     

Two novel norlignans from Gymnotheca chinensis

Two novel norlignans, gymnothedelignans A and B were isolated from the whole plants of Gymnotheca chinensis. These norlignans possess a rare 2/5 epoxy benzocycloheptanone skeleton. Their structures were established on the basis of 1D and 2D NMR spectral data analysis, and the absolute stereochemistry of gymnothedelignans A and B was further confirmed by single crystal X-ray diffraction analysis.     

Cytotoxic ent-kauranoid derivatives from Isodon rubescens

An extensive study of the diterpenoids produced by the species of Isodon rubescens, has led to the isolation of 12 new ent-kaurane diterpenoids, hebeirubescensins A-L (1-12), and 19 known analogues. Their structures were determined on the basis of spectroscopic analysis. Selected compounds were assayed for their inhibitory ability against human A549, HT-29, and K562 cells. Among them, hebeirubescensins B and C exhibited significant cytotoxicity with IC₅₀ values of <2.0 μM. The structure-activity relationships were discussed.     

New naphthoquinone and monoterpenoid from Plumbago zeylanica

New naphthoquinone 2 and new monoterpenoid 3 were isolated from the stems of Plumbago zeylanica, and their structures were determined on the basis of 2D NMR spectroscopy. Absolute configuration of 3 was established by synthesis of its enantiomer. The new naphthoquinone 2 showed potent inhibitory activity against nuclear factor κB (NF-κB), equivalent to that of parthenolide, a known potent inhibitor of NF-κB.