Diverse Ring-seco Limonoids from Munronia unifoliolata and Their Biological Activities

Twenty-two new limonoids,mufolinoids A—V(1—22),including six rings A,B-seco limonoids(1—6),twelve ring A-seco limonoids(7—18),four ring-intact limonoids(19—22),together with thirteen known compounds(23—35)were isolated from Munronia unifoliolata.Their structures including absolute configurations were elucidated by combination of NMR,HR-MS,single-crystal X-ray diffraction and calculations of ECD and NMR technologies.Compounds 24,25,33,34 could be significantly reversed the multidrug resistance of MCF-7/doxorubicin(DOX)cells,and the reversal fold(RF)was much higher than that of positive drug Verapamil.Compounds 24,28,and 29 exhibited significant anti-inflammatory activity with the IC50 values in the range of 17.7—39.4μmol/L.Furthermore,compound 29 could markedly inhibit the release of IL-1βby inhibiting the initiation and assembly of NLRP3 inflammasome,which demonstrates the great potential of limonoids as an anti-inflammatory agent.     

A novel 29-nor-3,4-seco-friedelane triterpene and a new guaiane sesquiterpene from the roots of Phyllanthus oxyphyllus

An unusual 29-nor-3,4-seco-friedelan-4(23),20(30)-dien-3-oic acid and a new 5-hydroxy-6,9-epoxyguaiane have been isolated along with other rare terpenes and lignans from Phyllanthus oxyphyllus roots. Their structures were elucidated from spectroscopic data. The radical scavenging properties of some of these compounds were evaluated. seco-Isolariciresinol showed strong antioxidant activity (IC₅₀ 0.017±0.001 mM).     

Chemical Constituents of Acanthochlamys bracteata

A novel nortriterpene, acanthochlamic acid (6), along with 18 known compounds has been isolated from the whole plants of Acanthochlamys bracteata P. C. Kao, a single species in family Acanthochlamydaceae which is endemic to the southwest of China. The structure of the novel nortriterpene was elucidated as 3,4-seco-3-norlup-4(23),20(29)-dien-2,28-dioic acid by spectroscopic techniques including 1D and 2D NMR spectroscopy and confirmed by X-ray crystallography.     

Mass spectra of Sceletium alkaloids

The mass spectra of several naturally occuring Sceletium alkaloids, as well as several synthetic variants, have been investigated. Techniques used include high resolution mass measurements, analysis of metastable transitions by the technique of ion defocusing and specific deuterium labeling in conjunction with low resolution mass spectrometry. Characteristic major fragmentation pathways have been determined for four basic structure types studied: the cis-3a-aryl-octahydroindole ring system, exemplified by mesembrine; its 2,3-pyrido analog, Sceletium A₄; the seco series of pyridine bases, represented by tortuosamine; and the seco analog of the mesembrine-type represented by tortuosamine; and the seco analog of the mesembrine-type represented by dehydrojoubertiamine.     

Two New Degraded Triterpenoids and a Novel seco‐Norabietane Diterpene from the Root Bark of Azadirachta indica

Three new compounds, the degraded ring C‐seco‐tetranortriterpenoid nimbolicidin ( 1 ), the degraded hexanortriterpenoid nimbocin ( 2 ), and the seco‐norabietane diterpene nimbocinin ( 3 ), were isolated from the root bark of Azadirachta indica A.Juss . Compound 1 is O‐bearing both at C(28) and C(29), which has been hitherto unreported in tetranortriterpenoids; 2 represents the first hexanortriterpenoid with a truncated apotirucallane (or apoeuphane) skeleton; 3 is an unprecedented seco‐norabietane. Spectroscopic data and chemical transformations of these compounds provided their complete structures.     

Synthesis of Novel D-Seco-Pregnenes

A new synthetic route was developed for the preparation of trans-3-hydroxy-16,17-seco-pregna-5,17(20)-dien-16-al, using Grob fragmentation as the key step. This seco-steroid contains a formyl group and an unsaturated side-chain in a sterically favourable position, and is therefore a promising starting material for the synthesis of novel condensed steroid heterocycles.     

Synthesis of Novel <Emphasis Type="Italic">D</Emphasis>-<Emphasis Type="Italic">Seco</Emphasis>-Pregnenes

Summary. A new synthetic route was developed for the preparation of trans-3-hydroxy-16,17-seco-pregna-5,17(20)-dien-16-al, using Grob fragmentation as the key step. This seco-steroid contains a formyl group and an unsaturated side-chain in a sterically favourable position, and is therefore a promising starting material for the synthesis of novel condensed steroid heterocycles.Received March 22, 2003; accepted April 22, 2003 Published online September 25, 2003     

Transformation of Azadiradione to Nimbocinol and 17β‐Hydroxynimbocinol,and Structure?Pesticidal‐Activity Relationship of Triterpenoids isolated from Azadirachta indica A. Juss. (Neem)

During studies on the structure? pesticidal‐activity relationship of Azadirachta indica constituents, azadiradione ( 1 ) was treated with methanolic K₂CO₃ to obtain 7‐deacetyl derivative nimbocinol ( 2 ). Unexpectedly, 17β‐hydroxynimbocinol ( 3 ), reported earlier as a natural product, was also formed. The structure? pesticidal‐activity relationship of triterpenoids 1 – 16 against Anopheles stephensi Liston is described towards understanding the active functionalities responsible for the pesticidal activity of triterpenoids having apoeuphane(apotirucallane) and gedunin skeleta. The pesticidal activities of triterpenoids 2 – 8 are reported for the first time.     

Total Synthesis of the Bicyclic Depsipeptide HDAC Inhibitors Spiruchostatins A and B, 5′′‐epi‐Spiruchostatin B,FK228 (FR901228) and Preliminary Evaluation of Their Biological Activity

The bicyclic depsipeptide histone deacetylase (HDAC) inhibitors spiruchostatins A and B, 5′′‐epi‐spiruchostatin B and FK228 were efficiently synthesized in a convergent and unified manner. The synthetic method involved the following crucial steps: i) a Julia–Kocienski olefination of a 1,3‐propanediol‐derived sulfone and a L ‐ or D ‐malic acid‐derived aldehyde to access the most synthetically challenging unit, (3S or 3R,4E)‐3‐hydroxy‐7‐mercaptohept‐4‐enoic acid, present in a D ‐alanine‐ or D ‐valine‐containing segment; ii) a condensation of a D ‐valine‐D ‐cysteine‐ or D ‐allo‐isoleucine‐D ‐cysteine‐containing segment with a D ‐alanine‐ or D ‐valine‐containing segment to directly assemble the corresponding seco‐acids; and iii) a macrocyclization of a seco‐acid using the Shiina method or the Mitsunobu method to construct the requisite 15‐ or 16‐membered macrolactone. The present synthesis has established the C5′′ stereochemistry of spiruchostatin B. In addition, HDAC inhibitory assay and the cell‐growth inhibition analysis of the synthesized depsipeptides determined the order of their potency and revealed some novel aspects of structure–activity relationships. It was also found that unnatural 5′′‐epi‐spiruchostatin B shows extremely high selectivity (ca. 1600‐fold) for class I HDAC1 (IC₅₀=2.4 nM ) over class II HDAC6 (IC₅₀=3900 nM ) with potent cell‐growth‐inhibitory activity at nanomolar levels of IC₅₀ values.     

Synthesis and antiviralactivity of 2,3-<Emphasis Type="Italic">seco</Emphasis>-derivatives of betulonic acid

A lupane 2,3-seco-aldehydoacid that was oxidized further to the 2,3-seco-diacid was synthesized by Beckmann fragmentation of the α-hydroxyoxime of betulonic acid. It was found that both 2,3-seco-derivatives were capable of suppresing reproduction of Herpes type 1 and flu A viruses (EC₅₀ from 1.9 to 21.3 μM).     

Triterpenoids and other Constituents from Euphorbia Humifusa

A novel lupane‐type triterpenoid, 3,4‐seco‐lupa‐4(23), 20(29)‐dien‐24‐hydroxy‐3‐oic acid (1) and a new cycloartane‐type triterpenoid, 23(E)‐cycloart‐23‐en‐25‐ethoxy‐3β‐ol (7), as well as eighteen known compounds, were isolated from the hot ethanol extract of the whole plant of Euphorbia humifusa Willd. The new structures were characterized by means of spectroscopic methods including 1D, 2D NMR and HRESIMS, and the known ones were established on the basis of comparing their NMR data with those of the corresponding compounds in the literature. In addition, cytotoxicity against selected cancer cell human gastric carcinoma (SGC‐7901) of compounds 1,3,4,6 were measured in vitro.     

A new 22,26-seco physalin steroid from Physalis angulata

Abstract

A new 22,26-seco physalin, physalin XI (1) together with 5 known compounds, were isolated from the dichloromethane extract of Physalis angulata L. The structure of isolated compounds was elucidated by spectroscopic analysis. The effects of isolated compounds on in vitro cytotoxicity were investigated. Compound 1 was assessed for its cytotoxicity against cancer cell lines (HepG2, HeLa, HuCCA-1, T47-D and A-549) and a normal cell line (MRC-5), and the result showed that it has no activity. Compounds 2 and 4 are highly toxic to H69AR and MDA-MB-23 cell lines. This property appears to be related to the presence of their conjugated double bond or epoxy groups and is a more reliable indication of toxicity than substitution on C(5)–C(6).     

Two new lanostane triterpenoids from Abies sachalinensis

The continuous chemical investigation on the ethyl acetate （EtOAc） soluble fraction of the MeOH extract afforded two new lanostane triterpenoid derivatives including one with a rearranged lanostane skeleton. They were identified as 3,4-seco-8-（14→13R）abeo-17,13-friedo-9β-lanosta-4（28）, 7,14（30）,24-tetraen-26,23-olide-23-hydroxy-3-oic acid （1） and 7,14-mariesa- dien-3oL-hydroxy-25-methoxy-26-oic acid （2）. Structural determination of these compounds were carried out by the spectral studies especially by the two digital （2D）-NMR and high-resolution MS experiences.     

A new 3,4-seco-cycloartane from the leaves of Hopea odorata Roxb.

A new 3,4-seco-cycloartane, identified as (24R,25S)-dihydroxy-26-O-nonadecylcarbonyloxy-3,4-secocycloarta-4(28)-en-3-oic acid (1), has been isolated from the leaves of Hopea odorata Roxb. (Dipterocarpaceae), together with the rare 3,4-seco-cycloart-4(28),24-diene-3,26-dioic acid (2 or abiesatrine J) and six other known compounds (3–8). Their structures were elucidated on the basis of both chemical and spectroscopic methods.     

Synthesis,Structural Reassignment,and Antibacterial Evaluation of 2,18‐Seco‐Lankacidinol B

Lankacidins are a group of polyketide natural products with activity against several strains of Gram‐positive bacteria. We developed a route to stereochemically diverse variants of 2,18‐seco‐lankacidinol B and found that the stereochemical assignment at C4 requires revision. This has interesting implications for the biosynthesis of natural products of the lankacidin class, all of which possessed uniform stereochemistry prior to this finding. We have evaluated 2,18‐seco‐lankacidinol B and three stereochemical derivatives against a panel of pathogenic Gram‐positive and Gram‐negative bacteria.     

Synthesis,Structural Reassignment,and Antibacterial Evaluation of 2,18‐Seco‐Lankacidinol B

Lankacidins are a group of polyketide natural products with activity against several strains of Gram‐positive bacteria. We developed a route to stereochemically diverse variants of 2,18‐seco‐lankacidinol B and found that the stereochemical assignment at C4 requires revision. This has interesting implications for the biosynthesis of natural products of the lankacidin class, all of which possessed uniform stereochemistry prior to this finding. We have evaluated 2,18‐seco‐lankacidinol B and three stereochemical derivatives against a panel of pathogenic Gram‐positive and Gram‐negative bacteria.     

<Emphasis Type="Italic">seco</Emphasis>-Kaurane skeleton diterpenoids from <Emphasis Type="Italic">Croton oblongifolius</Emphasis>

A new seco-kaurane type diterpenoid, ent-3,4-seco-17-oxo-kaur-4(19),15(16)-dien-3-oic acid, and a known compound, ent-3,4-seco-kaur-4(19),16(17)-dien-3-oic acid, were isolated from the stem bark of Croton oblongifolius. The structures of these compounds were established on the basis of spectroscopic data.     

Seco‐Tremulanes from Cultures of the Basidiomycete Flavodon flavus BCC 17421

A new seco‐tremulane, 11,12‐epoxy‐5,6‐secotremula‐1,6(13)‐dien‐5,12‐olide ( 1 ), was isolated together with the known compounds, conocenolides A ( 2 ) and B ( 3 ), tremulenediol A ( 4 ), tremulenolide A ( 5 ), and two lanostane triterpenoids, trametenolic acid B ( 6 ), and pinicolic acid A ( 7 ), from cultures of the basidiomycete Flavodon flavus BCC 17421. Interconversion of conocenolides A/B was demonstrated. Compound 1 exhibited weak cytotoxic activities, whereas tremulenediol A showed antiplasmodial activity (IC₅₀ 8.6 μg/ml). Pinicolic acid A exhibited activity against herpes simplex virus type‐1 (IC₅₀ 15 μg/ml) as well as cytotoxic activities.     

Application of mass spectrometry to the structural investigation of triterpenes. II—3,4-A-seco-triterpenoids

The mass spectral behaviour of a series of naturally occurring and synthetic 3,4-A-seco-triterpenes has been examined and fragmentations characteristic of the 3,4-A-seco function observed. Deuterium labelling has been used to investigate the origins of their characteristic fragments.     

Alpha-Glucosidase Inhibitory Diterpenes from Euphorbia antiquorum Growing in Vietnam

Bioactive-guided phytochemical investigation of Euphorbia antiquorum L. growing in Vietnam led to the isolation of five ent-atisanes, one seco-ent-atisane, and one lathyrane (ingol-type). The structures were elucidated as ent-1α,3α,16β,17-tetrahydroxyatisane (1), ethyl ent-3,4-seco-4,16β,17-trihydroxyatisane-3-carboxylate (2), ent-atisane-3-oxo-16β,17-acetonide (3), ent-3α-acetoxy-16β,17-dihydroxyatisane (4), ent-16β,17-dihydroxyatisane-3-one (5), calliterpenone (6), and ingol 12-acetate (7). Their chemical structures were unambiguously determined by analysis of one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) and high resolution mass spectrometry, as well as by comparison with literature data. Among them, 1 is a new compound while 2 is an ethylated artifact of ent-3,4-seco-4,16β,17-trihydroxyatisane-3-carboxylic acid, a new compound. Isolates were evaluated for alpha-glucosidase inhibition. Compound 3 showed the most significant inhibitory activity against alpha-glucosidase with an IC₅₀ value of 69.62 µM. Further study on mechanism underlying yeast alpha-glucosidase inhibition indicated that 3 could retard the enzyme function by noncompetitive.