New polyesters from Talaromyces flavus

Six new polyesters, talapolyesters A–F (1–4, 14, and 16), together with 11 known ones 15G256ν (5), 15G256ν-me (6), 15G256π (7), 15G256β-2 (8), 15G256α-2 (9), 15G256α-2-me (10), 15G256ι (11), 15G256β (12), 15G256α (13), 15G256α-1 (15), and 15G256ω (17), were isolated from the wetland soil-derived fungus Talaromyces flavus BYD07-13, and their structures were determined by NMR and MS spectroscopic data. Among them, 1–4 and 16 were assembled in a different manner from that of the known 256 polyesters. All the polyesters are composed of (R)-2,4-dihydroxy-6-(2-hydroxypropyl)benzoic acid and (R)-3-hydroxybutyric acid/(S)-3,4-dihydroxybutyric acid residues. The absolute configurations of the residues were determined by alkaline hydrolysis. The cytotoxicity against five tumor cell lines of these compounds was examined, and a tight structure–activity relationship is proposed.     

Structures of new alkaloids sessilifoliamides A-D from Stemona sessilifolia

Four new Stemona alkaloids, sessilifoliamides A-D (1-4), were isolated from the roots of Stemona sessilifolia, along with five known alkaloids, stenine (5), 2-oxostenine (6), stemoninoamide (7), tuberostemonone (8), and neotuberostemonol (9). The structures and absolute configurations of the new alkaloids were determined by the spectral studies (HRMS, IR, ¹H, ¹³C, and 2D NMR), single-crystal X-ray analyses, and chemical correlations. The absolute configuration of 7 was also determined by the modified Mosher's method.     

Absolute stereostructure of Andirolides A-G from the flower of Carapa guianensis (Meliaceae)

A new gedunin, three new mexicanolides and three new phragmalin-type limonoids named Andirolides A (1), B (2), C (3), D (4), E (5), F (6), and G (7) were isolated from oil of the flower of Carapa guianensis Aublet (Meliaceae). Their absolute stereostructures were determined by 2D NMR and CD spectra, and single-crystal X-ray analysis, and all compounds were confirmed to have the C-17βH configuration. Considering the similarity in CD spectra between Andirolide G (7) and the xyloccensins reported by Wu, we concluded that the structures of xyloccensins should be revised so as to have the absolute configuration of 17R.     

Formamidobisabolene-based derivatives from a sponge Axinyssa sp.

Chemical examination of a Chinese sponge Axinyssa sp. resulted in the isolation of 12 new formamidobisabolene-based analogues named axinyssines A–L (1–12), along with a new natural product (13) and three known formamidobisabolenes (14–16). Their structures were determined on the basis of extensive NMR and mass spectroscopic analyses in association with ICD data, Mosher reaction and chemical conversion for the assignment of absolute configurations. All compounds were evaluated for antitumor and antimicrobial activities.     

Gelegamines A-E: five new oxindole alkaloids from Gelsemium elegans

Five new oxindole alkaloids, gelegamines A-E (1-5), were isolated from the roots of Gelsemium elegans. Their structures were extensively elucidated on the basis of spectroscopic analysis. Among them, the epoxy ring (C-19/C-20) of gelegamine A (1) was assigned as α-orientation by ROESY experiment and DFT method at B3LYP/6-31g(d) level, and gelegamine B (2) is the first humantenine-type alkaloid with 19-(E) ethylidene configuration. The absolute configurations of gelegamines A-E (1-5) were established on biosynthetic consideration coupled with CD experiments.     

Holophyllin A,a rearranged abietane-type diterpenoid from the trunk of Abies holophylla

Holophyllin A (1), a novel rearranged abietane-type diterpenoid was isolated, together with a new diterpene glycoside, holophyllin B (2), from the trunk of Abies holophylla. The structures of 1 and 2 were established by extensive spectroscopic analyses and their absolute configurations were determined by ECD calculation. All the isolates were tested for their inhibitory effects on NO production in LPS-activated murine microglial cells.     

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.     

6,7-Seco-ent-kaurane-type diterpenoids from Isodon eriocalyx var. laxiflora

Twenty nine 6,7-seco-ent-kaurane-type diterpenoids including 18 new ones, laxiflorolides C–T (1–18), along with 21 known ones were obtained from Isodon eriocalyx var. laxiflora. Laxiflorolides E–G (3–5) are the first identified naturally occurring 6,7-seco-ent-kauranoids that feature a 3,6-epoxy unit, and laxiflorolide M (11) is the first identified naturally occurring 6-nor-6,7-seco-ent-kauranoid. The absolute configurations of compounds 1, 3, 6, and 11 were determined by single-crystal X-ray diffraction analyses. The cytotoxic activity of the isolates was evaluated by an MTT assay.     

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.     

Nortriterpenoids from Schisandra chinensis and their absolute configurational assignments by electronic circular dichroism study

Twelve new nortriterpenoids, namely wuweizidilactones J–P (1–7), schindilactones I–K (8–10), preschisanartanin N (11), and schisdilactone J (12), as well as 23 known analogues, were isolated from the leaves and stems of Schisandra chinensis. The absolute configurations of 1 and 11 were established by calculated electronic circular dichroism (ECD) spectra and that of 7 was confirmed by single-crystal X-ray diffraction. The absolute configurations of 2–6, 8, and 9 were determined by an empirical comparison of their experimental ECD spectra with that of 1. It is the first time that the ECD spectra of 18(13→14)-abeo-schiartane-, 18-norschiartane-, and schisanartane-type nortriterpenoids possessing an α,β-unsaturated-γ-lactone moiety are presented, this method providing an alternative means of obtaining absolute configurational assignments for these types of nortriterpenoids. All isolates were evaluated for their anti-acetylcholinesterase and anti-butyrylcholinesterase activities, and compounds 8, 13, 23, and 31 show anti-acetylcholinesterase activity at concentrations of 50 μM, with 12.7, 10.7, 16.6, and 32.1% inhibition, respectively.     

Chejuenolides A and B, new macrocyclic tetraenes from the marine bacterium Hahella chejuensis

Two new 17-membered carbocyclic tetraenes, chejuenolides A and B (1 and 2), have been isolated from the EtOAc extract of the marine bacterium Hahella chejuensis by various chromatographic methods. The structures and relative configurations of 1 and 2 were mainly determined by analysis of the NMR spectroscopic data, and their absolute configurations were assigned by application of modified Mosher method.     

The absolute configuration determination of naturally occurring diacetylenic spiroacetal enol ethers from Artemisia lactiflora

Six new naturally occurring diacetylenic spiroacetal enol ethers, Lactiflodiynes A-F (1-6), together with five known congeners (7-11), were isolated from the whole plant of Artemisia lactiflora (Compositae). The structures were elucidated by extensive spectroscopic methods, X-ray crystallography, chemical transformations, and CD. The absolute configuration of Lactiflodiyne A (1) was determined to be 2R, 5S, 6S, and 7R by an X-ray crystallographic diffraction experiment using Mo Kα radiation with the absolute parameter of 0.01(8). In combination with CD, the absolute configurations of compounds 2-11 were confirmed by chemical transformations using 1 as the starting material.     

Diterpenes and sesquiterpenes with anti-Coxsackie virus B3 activity from the stems of Illicium jiadifengpi

Seven new diterpenes, jiadifenoic acids J–P (1–7), two new sesquicarane sesquiterpenes, sesquicaranoic acids A and B (8 and 9), and four known compounds, were isolated from the stems of Illicium jiadifengpi. The trans-fused A/B ring junction in diterpenes was deduced from NMR data analysis and confirmed by single-crystal X-ray crystallography of 3. The absolute configurations of compounds 1 and 5 were determined using the Mo₂(OAc)₄-induced circular dichroism (ICD) method. Compounds 8 and 9 are a pair of C-10 epimers, and their absolute configurations were confirmed by analyzing their CD and ICD data. All of the isolated compounds were evaluated in vitro for their antiviral activities against Coxsackie virus B3 (CVB3). Among the isolated compounds, 4, 5, 7, 10, and 11 exhibited reasonable activity against CVB3, with IC₅₀ values of 7.0–22.2 μmol/mL and selective index values (SI=TC₅₀/IC₅₀) of 49.3, 37.1, 31.3, 45.6 and 40.9, respectively.     

Ivorenoids A–F: limonoids from Khaya ivorensis

Six new limonoids, ivorenoids A–F (1–6), along with ten known analogues, were isolated from an ethanolic extract of the stems of Khaya ivorensis. Their structures were elucidated on the basis of spectroscopic analyses. Compounds 1 and 2 possessed a rare rearranged skeleton of khayanolides and a unique γ-lactone (C-16/C-8) replacing the common and characteristic δ-lactone D-ring (C-16/C-17) of limonoids. A mechanism of the interesting deuteration of H-2 and H-15β of 1, and H-15β of the solvent CD₃OD due to the keto–enol tautomerism was demonstrated. Compounds 3 and 6 showed moderate activity against HL-60 cell line with IC₅₀ values of 15.3 and 17.5 μM, respectively.     

Durumolides A-E, anti-inflammatory and antibacterial cembranolides from the soft coral Lobophytum durum

Chemical investigations on the acetone extract of the soft coral Lobophytum durum have afforded five new cembranoids with a trans-fused α-methylene-γ-lactone, durumolides A-E (1, 6, and 8-10), and five previously characterized cembrane-based diterpenoids (2-5 and 7). The structures of the isolated metabolites were elucidated through extensive spectroscopic analyses, while the relative stereochemistry of 4 was confirmed by X-ray diffraction analyses. Moreover, the absolute configurations of 3-5 and 8 were established by application of modified Mosher's method. The anti-inflammatory effects, antibacterial activities, and inhibition assay of HCMV (Human cytomegalovirus) endonuclease activity of these isolated metabolites 1-10 were evaluated in vitro.     

Rakanmakilactones A-F, new cytotoxic sulfur-containing norditerpene dilactones from leaves of Podocarpus macrophyllus var. maki

Six new S-containing norditerpene dilactones, rakanmakilactones A-F (5-10), were isolated from the leaves of Podocarpus macrophyllus D. Don var. maki Endl., along with four known norditerpene dilactones (1-4). Their structures, stereochemistry and absolute configurations were determined by spectroscopic studies (HRMS, IR, ¹H, ¹³C and 2D NMR), and single-crystal X-ray analyses. Rakanmakilactones were found to have a cytotoxic effect against P388 murine leukemia cells.     

Cespitulactams A, B, and C, three new nitrogen-containing diterpenes from Cespitularia taeniata May

Three new nitrogen-containing diterpenoids, designated cespitulactams A (1), B (2), and C (3), were isolated from Cespitularia taeniata May. Compounds 1-3 are novel structures having a phenylethyl amino side at C-10 and with an amide function at C-20. Their structures were determined on the basis of extensive spectroscopic analysis and chemical correlation. The cytotoxicity of 1 and its monoacetate (6) were also evaluated against human cancer cell lines.     

Penilactones A and B, two novel polyketides from Antarctic deep-sea derived fungus Penicillium crustosum PRB-2

Two highly oxygenated polyketides, penilactones A and B (1 and 2), containing a new carbon skeleton formed from two 3,5-dimethyl-2,4-diol-acetophenone units and a γ-butyrolactone moiety, together with five known compounds (3-7) were isolated from an Antarctic deep-sea derived fungus Penicillium crustosum PRB-2. Penilactones A and B possess antipodal absolute stereochemistries. Their structures were elucidated by spectroscopic methods, and their absolute configurations were assigned by single-crystal X-ray diffraction and CD analyses. A plausible biogenetic pathway for 1-2 is proposed.     

Chukvelutilides A-F, phragmalin limonoids from the stem barks of Chukrasia tabularis var. velutina

Chukvelutilides A-F (1-6), a new class of C-15-acyl phragmalin type limonoids, featuring a C-16/C-30 δ-lactone ring, were isolated from Chukrasia tabularis var. velutina. These compounds are suggested to possess a three- or four-carbon enolized acyl substituent at C-15 through a plausible biosynthetic origin. Their structures were elucidated by extensive spectroscopic means, and that of 1 was confirmed by single-crystal X-ray diffraction.     

Bioactive pregnane-type steroids from the soft coral Scleronephthya gracillimum

Nine new steroids, sclerosteroids A-I (1, 5, 6, 8-13), along with 18 known metabolites (2-4, 7, 14-27), were isolated from the soft coral Scleronephthya gracillimum. These structures were elucidated on the basis of detailed spectroscopic analysis. The absolute configurations of sugar moieties in steroidal glycosides 10-13 were determined by HPLC analysis of the o-tolylthiocarbamate derivatives of the liberated sugars from hydrolysis of these steroidal giycosides. Cytotoxic and anti-inflammatory activities of these compounds were measured in vitro.