A new cucurbitacin D related 16,23-epoxy derivative and its isomerization products

[reaction: see text] A new (23S,24Z)-16,23-epoxy cucurbitacin derivative was isolated from Ecballium elaterium L. (Cucurbitaceae) fruit juice along with known cucurbitacin derivatives. Structure elucidation of these derivatives was accomplished by NMR spectroscopy and mass spectrometry from HPLC-MS data. Isomerization of the epoxy derivative was monitored by 1D and 2D NMR experiments. The configuration of the reaction products was elucidated as (23R,24E) and (23R,24Z), and a mechanism for the acid-catalyzed rearrangement process is proposed.     

Synthesis, structure, and properties of supramolecular charge-transfer complexes between bis(18-crown-6)stilbene and ammonioalkyl derivatives of 4,4'-bipyridine and 2,7-diazapyrene

4,4'-Bipyridine and 2,7-diazapyrene derivatives (A) having two ammonioalkyl N-substituents were synthesized. The complex formation of these compounds with bis(18-crown-6)stilbene (D) was studied by spectrophotometry, cyclic voltammetry, (1)H NMR spectroscopy, and X-ray diffraction analysis. In MeCN, π-donor D and π-acceptors A form supramolecular 1:1 (D·A) and 2:1 (D·A·D) charge-transfer complexes. The D·A complexes have a pseudocyclic structure as a result of ditopic binding of the ammonium groups to the crown-ether fragments. The better the geometric matching between the components, the higher the stability of the D·A complexes (log K up to 9.39). A key driving force of the D·A·D complex formation is the excessive steric strain in the precursor D·A complexes. The pseudocyclic D·A complexes involving the ammoniopropyl derivative of 4,4'-bipyridine were obtained as single crystals. Crystallization of the related ammonioethyl derivative was accompanied by transition of the D·A complexes to a structure of the (D·A)(m) coordination polymer type.     

Convenient synthesis of 3,4-methano-1,2,3, 4-tetrahydroisoquinoline-3-carboxylic acid and its derivatives as doubly constrained nonproteinogenic amino acid derivatives

Three strategies for the synthesis of the novel, doubly constrained, 3,4-methano-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid and its derivatives were evaluated. Only cyclocondensation of the mono(triphenyl)phosphonium salt derived from 1, 2-bis(bromomethyl)benzene with N-alkoxycarbonyloxamates in 1, 2-dimethoxyethane in the presence of potassium carbonate and subsequent cyclopropanation with dimethylsulfoxonium methylide in dimethyl sulfoxide furnished suitable O- and N-protected derivatives of 3,4-methano-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid in a convenient way. A detailed 2D DQF-COSY and 2D NOESY NMR analysis of the rotational isomerism of the latter bicyclic amino acid derivatives was performed. Various O- and N-protection protocols were worked out to afford access to a whole range of new derivatives of the title amino acid, suitable for peptide synthesis.     

Beilschmiedic Acids F and G,Further Endiandric Acid Derivatives from Beilschmiedia anacardioides

Two new endiandric acid derivatives, beilschmiedic acid F ( 1 ) and beilschmiedic acid G ( 2 ), together with three known constituents, beilschmiedic acid A, beilschmiedic acid C, and sitosterol 3‐β‐D ‐glucopyranoside, were isolated from the stem bark of Beilschmiedia anacardioides. Their structures were elucidated mainly by using a combination of 1D‐ and 2D‐NMR techniques. The structure and relative configuration of beilschmiedic acid G ( 2 ) was also confirmed by X‐ray crystallographic analysis.     

Complete assignments of 1H and 13C NMR data for ten phenylpiperazine derivatives

Ten phenylpiperazine derivatives were designed and synthesized. The first complete assignments of (1)H and (13)C NMR chemical shifts for these phenylpiperazine derivatives were achieved by means of 1D and 2D NMR techniques, including (1)H-(1)H COSY, HSQC and HMBC spectra.     

Complete assignment of (1)H and (13)C NMR data of dihydroxyflavone derivatives

Six flavone derivatives were studied. Previously reported NMR data of three of these derivatives were corrected and the NMR data for the other three derivatives not studied previously were completely assigned on the basis of the basic 1D and 2D NMR experiments and molecular modeling.     

穿心莲内酯硫酸酯化反应体系中四个新的衍生物的分离与表征

通过色谱方法, 从复杂的穿心莲内酯硫酸酯化反应体系中分离获得4个新的穿心莲内酯衍生物, 应用谱学方法进行了表征. 主要利用1H NMR, 13C NMR, DEPT, 1H-1H COSY, HSQC, HMBC及NOSEY等1D和2D NMR技术, 并通过与母体化合物NMR数据的对比分析, 鉴定这4个化合物分别为3,19-二羟基-8,11,13-赖百当三烯-15,16-内酯(1), 3-羟基-8,11,13-赖百当三烯-15,16-内酯-19-硫酸酯(2), 8,11,13-赖百当三烯-15,16-内酯-3,19-二硫酸酯(3), 3-羟基- 8(R)-12(S)-8(12)-环氧-13-赖百当烯-15,16-内酯-19-硫酸酯(4).     

A Novel 19,21‐Secohetisan Diterpenoid Alkaloid from Aconitum tanguticum

A novel 19,21‐secohetisan diterpenoid alkaloid, tangutisine A ( 1 ), was isolated from Aconitum tanguticum (Maxim .) Stapf . Its structure was determined by HR‐EI‐MS and 1D‐ and 2D‐NMR spectroscopy and by comparison with the data of known 19,21‐secohetisan derivatives.     

Trichodermatides A-D, novel polyketides from the marine-derived fungus Trichoderma reesei

Four new polyketide derivatives, Trichodermatides A-D (1-4) were isolated from the marine-derived fungus Trichoderma reesei. Trichodermatide A (1) is an unprecedented example of a polyketide with a ketal-containing pentacyclic skeleton. The chemical structures and absolute configurations of compounds 1-4 were elucidated by extensive spectroscopic methods, especially 2D NMR and CD spectral analysis, and supported by their proposed biosynthesis pathway. The cytotoxicity of 1-4 was evaluated against A375-S2 human melanoma cell line.     

Regioselective synthesis and structural elucidation of 1,4-disubstituted 1,2,3-triazole derivatives using 1D and 2D NMR spectral techniques

Regioselective synthesis of 2-[1-(2-oxo-2-phenylethyl)-1H-[1,2,3]triazol-4-ylmethoxy]-benzaldehyde derivatives was achieved by [3 + 2] cycloaddition reaction of 2-(prop)-2-ynyloxy-benzaldehyde derivatives with phenacyl azide. The regiochemistry and the spectral assignments of the synthesized triazole derivatives were studied using both 1D and 2D NMR spectral techniques in solution.     

Complete assignment of 1H and 13C NMR data of pravastatin derivatives

The complete ¹H and ¹³C NMR data of 27 pravastatin derivatives are presented. Assignment was achieved by use of 1D and 2D NMR experiments (selective 1D NOE, COSY, NOESY, HSQC, HMBC). Copyright © 2008 John Wiley & Sons, Ltd.     

Five new nervogenic acid derivatives from Liparis nervosa

Five new nervogenic acid derivatives(1-5) have been isolated from Liparis nervosa(Thunb.ex A.Murray) Lindl.Their structures were elucidated on the basis of extensive spectroscopic analysis,including 1D NMR,2D NMR,and HR-ESI-MS.     

Cytotoxic lupane-, secolupane-, and oleanane-type triterpenes from Viburnum awabuki

Bioassay-guided fractionation of the methanolic extract of Viburnum awabuki afforded two new lupane triterpene derivatives; 6 beta-hydroxyl-3,20-dioxo-30 norlupane-28-oic acid (1) and 3,4-secolup-4,20-dihydroxy-3,28-dioic acid-3-oic acid methyl ester (2), along with seven known lupane and oleanane-type triterpenes (3-9). The structure of the isolated compounds was assigned using different spectroscopic techniques including 1D and 2D NMR. The 13CNMR data of compounds 5 and 9 is reported for the first time. Triterpenes 1, 2, and 7-9 showed in vitro cytotoxic activity against several tumor cell lines.     

Two-dimensional and variable temperature 31P solid-state NMR studies of single crystals containing symmetrical/unsymmetrical bis[6-O,6-O'-(1,2:3,4-diisopropylidene-alpha-D- galactopyranosyl)thiophosphoryl] dichalcogenides

The organisation and phase transition of single crystals containing three isostructural bis[6-O,6-O'-(1,2:3,4-diisopropylidene-alpha- D-galactopyranosyl)thiophosphoryl] dichalcogenide derivatives: disulfide 1, diselenide 2 and mixed seleno-sulfide 3, was deduced upon 1D, 2D and variable temperature 31P NMR experiments.     

Two New Octahydronaphthalene Derivatives from Trichoderma spirale,an Endophytic Fungus Derived from Aquilaria sinensis

Two new octahydronaphthalene derivatives, trichodermic acid A ( 1 ) and trichodermic acid B ( 2 ), along with a known analog, trichodermic acid ( 3 ), and a known modified dipeptide, trichodermamide A ( 4 ), were isolated from the extract of Trichoderma spirale, an endophytic fungus present in the medicinal plant Aquilaria sinensis. The structures of these compounds were established by extensive analysis of their spectroscopic data including 1D‐ and 2D‐NMR and MS data.     

Diastereoselective one-pot synthesis of novel ABCD-fused chromeno[2,3-d]pyrazolo[3,4-b]pyridines

A new aspect concerning chromone chemistry leading to the one-pot synthesis of functionalized novel ABCD-fused chromenopyrazolopyridines has been described. The synthesis involves a multicomponent reaction of chromone-3-benzoylhydrazones with isocyanides and acetylenedicarboxylates, whereupon novel complex tetracyclic benzopyrone derivatives containing three stereogenic centres were formed. The structure elucidation of the products was accomplished by 1D and 2D NMR experiments and confirmed by X-ray crystallographic analysis. Full assignment of all ¹H and ¹³C NMR chemical shifts has been unambiguously achieved. The reaction mechanism is also discussed. In addition, eight chromenopyrazolopyridine derivatives were tested for possible biological activity (antioxidant and lipid peroxidation inhibition).     

Reactions of β-keto thioamides with α,β-unsaturated aldehydes. Synthesis of 6-hydroxypiperidine-2-thiones and 6H-thiopyrans

Mixtures of 3-benzoylated and 3-unsubstituted 6-hydroxypiperidine-2-thione derivatives were formed in the reaction of benzoyl(acetyl) thioacetamides with α,β-unsaturated aldehydes in refluxing ethanol in the presence of catalytic amounts of triethylamine. A mechanism for the debenzoylation was proposed. Derivatives of 6H-thiopyran were obtained when an analogous reaction was carried out in refluxing pyridine. The structures of all compounds were determined with the aid of 1D NMR (¹H, ¹³C, ¹³C-DEPT-135) and 2D NMR (¹H, ¹H COSY, ¹H, ¹H NOESY, ¹³C, ¹H COSY) spectroscopy.     

Wedelolides A and B: novel sesquiterpene delta-lactones, (9R)-eudesman-9,12-olides, from Wedelia trilobata

Two new sesquiterpene lactones, wedelolides A (1) and B (2), were isolated by bioassay-guided fractionation from the leaves of Wedelia trilobata, together with known trilobolides 6-O-isobutyrate (3) and 6-O-methacrylate (4). The compounds 1 and 2 were the first examples of an unprecedented framework: a novel sesquiterpene delta-lactone, (9R)-eudesman-9,12-olide. The structures of the antimalarial wedelolides A (1) and B (2) were determined on the basis of MS and 2D NMR spectral analysis. The absolute configuration of eight carbon stereocenters of compounds 1 and 2 was determined to be 1S,4S,5S,6R,7S,8S,9R,10S by mean of auxiliary chiral MTPA derivatives.     

New Biphenyl Constituents from Garcinia oblongifolia

Four new biphenyl derivatives, oblongifoliagarcinines A–D ( 1 – 4 ), were isolated on the chemical investigation of the stems and leaves of Garcinia oblongifolia. The structures of 1 – 4 were established on the basis of 1D‐ and 2D‐NMR and other spectroscopic analyses.     

Stoichiometry-controlled cycloaddition of azomethine ylide with dipolarophiles: chemoselective and regioselective synthesis of bis- and tris-spirooxindole derivatives

A new series of bis- and tris-spirooxindole derivatives have been synthesized by controlling the molar equivalent of in situ generated azomethine ylides in [3+2]-cycloaddition reactions with dipolarophiles. The structural elucidation on the basis of IR, ¹H NMR, ¹³C NMR, and mass spectral data of these compounds established the highly chemoselective and regioselective formation of spirooxindole derivatives. Single crystal X-ray analysis of compound 4g and 2D NMR analysis of compound 5a confirmed the structures of bis- and tris-spirooxindole derivatives.