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Showing papers in "Helvetica Chimica Acta in 2011"


Journal ArticleDOI
TL;DR: The enantioselective Michael addition of aldehydes to nitro alkenes is known to be acid-catalyzed (see as mentioned in this paper for a mechanistic investigation).
Abstract: The amine-catalyzed enantioselective Michael addition of aldehydes to nitro alkenes (Scheme 1) is known to be acid-catalyzed (Fig. 1). A mechanistic investigation of this reaction, catalyzed by diphenylprolinol trimethylsilyl ether is described. Of the 13 acids tested, 4-NO2C6H4OH turned out to be the most effective additive, with which the amount of catalyst could be reduced to 1 mol-% (Tables 2–5). Fast formation of an amino-nitro-cyclobutane 12 was discovered by in situ NMR analysis of a reaction mixture. Enamines, preformed from the prolinol ether and aldehydes (benzene/molecular sieves), and nitroolefins underwent a stoichiometric reaction to give single all-trans-isomers of cyclobutanes (Fig. 3) in a [2+2] cycloaddition. This reaction was shown, in one case, to be acid-catalyzed (Fig. 4) and, in another case, to be thermally reversible (Fig. 5). Treatment of benzene solutions of the isolated amino-nitro-cyclobutanes with H2O led to mixtures of 4-nitro aldehydes (the products 7 of overall Michael addition) and enamines 13 derived thereof (Figs. 6–9). From the results obtained with specific examples, the following tentative, general conclusions are drawn for the mechanism of the reaction (Schemes 2 and 3): enamine and cyclobutane formation are fast, as compared to product formation; the zwitterionic primary product 5 of C,C-bond formation is in equilibrium with the product of its collapse (the cyclobutane) and with its precursors (enamine and nitro alkene); when protonated at its nitronate anion moiety the zwitterion gives rise to an iminium ion 6, which is hydrolyzed to the desired nitro aldehyde 7 or deprotonated to an enamine 13. While the enantioselectivity of the reaction is generally very high (>97% ee), the diastereoselectivity depends upon the conditions, under which the reaction is carried out (Fig. 10 and Tables 1–5). Various acid-catalyzed steps have been identified. The cyclobutanes 12 may be considered an off-cycle ‘reservoir’ of catalyst, and the zwitterions 5 the ‘key players’ of the process (bottom part of Scheme 2 and Scheme 3).

172 citations


Journal ArticleDOI
TL;DR: In this article, a Pd2+-Exchanged graphite oxide (GO) serves as a precatalyst for the formation of Pd-nanoparticles which are then deposited on the highly functionalized carbonaceous support.
Abstract: Pd2+-Exchanged graphite oxide (GO) serves as a precatalyst for the formation of Pd-nanoparticles which are then deposited on the highly functionalized carbonaceous support This versatile, air-stable, and ligand-free system was applied successfully to SuzukiMiyaura couplings of some aryl chlorides and to the MizorokiHeck as well as the Sonogashira reaction showing relatively high activities and good selectivities Like with other ligand-free supported systems, the reaction proceeded dominantly by a homogeneous mechanism, but attack of an aryl iodide to Pd-nanoparticles can be excluded as substantial contribution to the entire catalytic process Beside its straightforward preparation and its stability in air, the system combines the advantages of both homogeneous and heterogeneous catalysis

52 citations


Journal ArticleDOI
TL;DR: In this article, reactions of biacetyl (=butane-2,3-dione) with (N-isocyanimino)triphenylphosphorane in the presence of aromatic carboxylic acids proceed smoothly at room temperature and under neutral conditions to afford 3-(5-aryl-1,3,4-oxadiazol-2-yl)-3-hydroxybutan-1-one derivatives in high yields.
Abstract: Reactions of biacetyl (=butane-2,3-dione) with (N-isocyanimino)triphenylphosphorane in the presence of aromatic carboxylic acids proceed smoothly at room temperature and under neutral conditions to afford 3-(5-aryl-1,3,4-oxadiazol-2-yl)-3-hydroxybutan-2-one derivatives in high yields.

47 citations


Journal ArticleDOI
TL;DR: New Approach for the Construction of the Coumarin Frame and Application in the Total Synthesis of Natural Products as mentioned in this paper is a new approach for the construction of the coumarin frame and application in the total synthesis of natural products.
Abstract: New Approach for the Construction of the Coumarin Frame and Application in the Total Synthesis of Natural Products

44 citations


Journal ArticleDOI
TL;DR: In this paper, N-Heterocyclic carbene (NHC) complexes with bromo(1,3-dibenzyl)-1H-imidazol-3-ium bromide (1a), 3-(4-cyanobenzyl]-1-methyl-1-hexadec-benzimidrazolium bormide (MTT)-bromide(1b), and 3-(1-(4,5dimethylthiazol-2-yl)-2,5-dip
Abstract: N-Heterocyclic carbene (NHC) complexes bromo(1,3-dibenzyl-1,3-dihydro-2H-imidazol-2-ylidene)silver(I) (2a), bromo[1-(4-cyanobenzyl)-3-methyl-1,3-dihydro-2H-imidazol-2-ylidene]silver(I) (2b), and bromo[1-(4-cyanobenzyl)-3-methyl-1,3-dihydro-2H-benzimidazol-2-ylidene]silver(I) (2c) were prepared by the reaction of 1,3-dibenzyl-1H-imidazol-3-ium bromide (1a), 3-(4-cyanobenzyl)-1-methyl-1H-imidazol-3-ium bromide (1b), and 3-(4-cyanobenzyl)-1-methyl-1H-benzimidazol-3-ium bromide (1c), respectively, with silver(I) oxide. NHC Complexes chloro(1,3-dibenzyl-1,3-dihydro-2H-imidazol-2-ylidene)gold(I) (3a), chloro[1-(4-cyanobenzyl)-3-methyl-1,3-dihydro-2H-imidazol-2-ylidene]gold(I) (3b), and chloro[1-(4-cyanobenzyl)-3-methyl-1,3-dihydro-2H-benzimidazol-2-ylidene]gold(I) (3c) were prepared via transmetallation of corresponding (bromo)(NHC)silver(I) complexes with chloro(dimethylsulfido)gold(I). The complex 3a was characterized in two polymorphic forms by single-crystal X-ray diffraction showing two rotamers in the solid state. The cytotoxicities of all three bromo(NHC)silver(I) complexes and three (chloro)(NHC)gold(I) complexes were investigated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bormide (MTT)-based preliminary in vitro testing on the Caki-1 cell line in order to determine their IC50 values. (Bromo)(NHC)silver(I) complexes 2a–2c and (chloro)(NHC)gold(I) complexes 3a–3c were found to have IC50 values of 27±2, 28±2, 34±6, 10±1, 12±5, and 12±3 μM, respectively, on the Caki-1 cell line.

40 citations


Journal ArticleDOI
TL;DR: In this article, the fungus Aspergillus ustus isolated from the Mediterranean sponge Suberites domuncula yielded the five new ophiobolin-type sesterterpenoids 1−5 and the two new pyrrolidine alkaloids 6 and 7, together with the known compound aurantiamine and cerebroside D.
Abstract: Chemical examination of the fungus Aspergillus ustus isolated from the Mediterranean sponge Suberites domuncula yielded the five new ophiobolin-type sesterterpenoids 1–5 and the two new pyrrolidine alkaloids 6 and 7, together with the known compound aurantiamine and cerebroside D. The structures of the new compounds were unambiguously elucidated on the basis of extensive spectroscopic-data analysis (1D- and 2D-NMR, MS, and UV) and comparison with literature data. All compounds were evaluated for their cytotoxicity against murine lymphoma cell line L5178Y.

40 citations


Journal ArticleDOI
TL;DR: Oleraceins F and G were isolated from Portulaca oleracea L, and their structures were determined as methyl (2S)-6-[(β-D-glucopyranosyl)oxy]-2,3-dihydro-5-hydroxy-1-[(2E)-3-(4-hydroxyphenyl)prop-2-enoyl]-1H-indole-2 carboxylate.
Abstract: Two alkaloids, oleraceins F and G, were isolated from Portulaca oleracea L, and their structures were determined as methyl (2S)-6-[(β-D-glucopyranosyl)oxy]-2,3-dihydro-5-hydroxy-1-[(2E)-3-(4-hydroxy-3-methoxyphenyl)prop-2-enoyl]-1H-indole-2-carboxylate and methyl (2S)-6-[(β-D-glucopyranosyl)oxy]-2,3-dihydro-5-hydroxy-1-[(2E)-3-(4-hydroxyphenyl)prop-2-enoyl]-1H-indole-2-carboxylate, based on their spectroscopic data Oleraceins F and G exhibited scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, with EC50 values of 2100 and 3769 μM, respectively

38 citations


Journal ArticleDOI
TL;DR: In this paper, the 1,3,4-oxadiazole derivatives were obtained via an intramolecular aza-Wittig reaction of the iminophosphorane intermediate.
Abstract: The 1 : 1 imine intermediate 7 generated by the addition of a primary amine 2 to chloroacetone (1) is trapped by (isocyanoimino)triphenylphosphorane (4) in the presence of an aromatic carboxylic acid 3 and leads to the formation of the corresponding iminophosphorane intermediate 9 (Scheme 2). The 1,3,4-oxadiazole derivatives 5 are then formed via an intramolecular aza-Wittig reaction of the iminophosphorane intermediate 9. The reactions were completed under neutral conditions at room temperature. The fully substituted 1,3,4-oxadiazole derivatives 5 were produced in high yields (Table).

37 citations


Journal ArticleDOI
TL;DR: Four new dimeric naphtho-γ-pyrones are isolated from the mangrove endophytic fungus Aspergillus tubingensis cultivated in solid rice medium and display inhibitory activities against tumor cell lines of MCF-7, MDA-MB-435, Hep3B, Huh7, SNB19, and U87 MG.
Abstract: Four new dimeric naphtho-γ-pyrones, named rubasperone D (1), rubasperone E (2), rubasperone F (3), and its atropisomer rubasperone G (4), together with four known monomeric naphtho-γ-pyrones, TMC 256 A1 (5), rubrofusarin B (6), fonsecin (7), and flavasperone (8), were isolated from the mangrove endophytic fungus Aspergillus tubingensis (GX1-5E) cultivated in solid rice medium. Their structures were elucidated by spectroscopic methods, including IR, 1D- and 2D-NMR, and MS. In the in vitro cytotoxicity assays, 5 displayed inhibitory activities against tumor cell lines of MCF-7, MDA-MB-435, Hep3B, Huh7, SNB19, and U87 MG with IC50 values between 19.92 and 47.98 μM. Compounds 1, 6, and 8 also showed mild cytotoxic activity.

36 citations


Journal ArticleDOI
TL;DR: In the in vitro antitumor assay, compounds 2–6 showed mild cytotoxicity against three tumor cell lines (MCF-7, SF-268, and NCI-H460) and were identified by comparison of their MS and NMR data with those reported in the literature.
Abstract: Two new cytochalasins, 18-deoxycytochalasin Q (1) and 21-O-deacetylcytochalasin Q (2), together with four known analogues, cytochalasin Q (3), 19,20-epoxycytochalasin Q (4), 21-O-deacetyl-19,20-epoxycytochalasin Q (5), and cytochalasin D (6), were isolated from the fungus Xylaria sp. SCSIO156 originated from the South China Sea marine sediment. The structures of 1 and 2 were elucidated by MS and 1D- and 2D-NMR data analyses, and comparison with known compounds. The known compounds 3–6 were identified by comparison of their MS and NMR data with those reported in the literature. In the in vitro antitumor assay, compounds 2–6 showed mild cytotoxicity against three tumor cell lines (MCF-7, SF-268, and NCI-H460).

32 citations


Journal ArticleDOI
TL;DR: In this article, a phytochemical investigation on bulbs of Lycoris radiata resulted in the isolation of three new Amaryllidaceae alkaloids, named 5,6-dehydrodihydrolycorine (1), 6 beta-acetoxycrinamine (2), and (+)-8-O-acetylhomolycorine alpha-Noxide (3), together with eleven known alkaloid, 4-14.
Abstract: A phytochemical investigation on bulbs of Lycoris radiata resulted in the isolation of three new Amaryllidaceae alkaloids, named 5,6-dehydrodihydrolycorine (1), 6 beta-acetoxycrinamine (2), and (+)-8-O-acetylhomolycorine alpha-N-oxide (3), together with eleven known alkaloids, 4-14. The structures of the new alkaloids were established by means of spectroscopic methods, and the known compounds were identified by comparison of their data with those in the literature. Compound 2 showed cytotoxicity against HL-60, A-549, and MCF-7 cells, with IC(50) values of 8.1, 24.3, and 15.0 mu m, respectively.

Journal ArticleDOI
TL;DR: Two new ent-kaurane diterpenes, wedelidins A (8) and B (9), together with eighteen other constituents, including the sesquiterpenoids 1 and 2, triterpenoid 10 and 11, steroids 12-14, and flavonoids 15-17 as well as benzene derivatives 18-20, were isolated from the aerial parts of Wedelia trilobata as mentioned in this paper.
Abstract: Two new ent-kaurane diterpenes, wedelidins A (8) and B (9), together with eighteen other constituents, including the sesquiterpenoids 1 and 2, ent-kaurane diterpenes 3–7, triterpenoids 10 and 11, steroids 12–14, and flavonoids 15–17 as well as benzene derivatives 18–20, were isolated from the aerial parts of Wedelia trilobata. The structures of wedelidins A (8) and B (9) were elucidated by extensive spectroscopic analyses (including UV, IR, NMR, and MS). Furthermore, the structures of compounds 2 and 3 were confirmed by X-ray single-crystal diffraction analyses.

Journal ArticleDOI
TL;DR: The four-component reaction of dimethyl acetylenedicarboxylate (DMAD), aromatic aldehydes, and malononitrile (propanedinitrile) leads to polyfunctionalized 1,4-dihydropyridine derivatives as discussed by the authors.
Abstract: The four-component reaction of dimethyl acetylenedicarboxylate (=dimethyl but-2-ynedioate; DMAD), aromatic aldehydes, and malononitrile (=propanedinitrile) leads to polyfunctionalized 1,4-dihydropyridine derivatives. The reaction proceeds at room temperature and in the presence of a catalytic amount (20%) of (NH4)2HPO4 as a base in aqueous media.

Journal ArticleDOI
TL;DR: A new indole alkaloid, streptomycindole, and a known related compound, N-phenylacetyl-L-tryptophan, have been isolated from Streptomyces sp.
Abstract: A new indole alkaloid, streptomycindole (1), and a known related compound, N-phenylacetyl-L-tryptophan (2), have been isolated from Streptomyces sp. DA22, associated with South China Sea sponge Craniella australiensis. Their structures were established on the basis of a combination of mass spectrometry, 1H- and 13C-NMR spectroscopic analyses, and chemical methods.

Journal ArticleDOI
TL;DR: Two new cyclic pentapeptides, named versicotides A and B, were obtained from a marine-derived fungus strain ZLN-60, identified as Aspergillus versicolor, and their structures were established on the basis of chemical and spectroscopic evidence.
Abstract: Two new cyclic pentapeptides, named versicotides A (1) and B (2), were obtained from a marine-derived fungus strain ZLN-60, identified as Aspergillus versicolor. Their structures were established on the basis of chemical and spectroscopic evidence. Versicotides are new cyclic pentapeptides which contain an L-alanine residue, two anthranilic acid (=2-aminobenzoic acid) residues, and two N-methyl-L-alanine residues. Antitumor activities were evaluated by the SRB and MTT methods.

Journal ArticleDOI
TL;DR: In this paper, the synthesis of substituted salicylaldehydes with 4-chloro-3-oxobutanoate in the presence of piperidine in CH2Cl2 at room temperature, in good yields.
Abstract: Ethyl 2-(chloromethyl)-2-hydroxy-2H-chromene-3-carboxylates 2a–2j have been synthesized by reaction of substituted salicylaldehydes with ethyl 4-chloro-3-oxobutanoate, in the presence of piperidine in CH2Cl2 at room temperature, in good yields.

Journal ArticleDOI
TL;DR: In this paper, a clean, simple and efficient method for the synthesis of spiro compounds by three-component reaction of isatins or acenaphthylene-1,2-dione, 1,3-diphenyl-1H-pyrazoles-5-amines, and tetronic acid was developed.
Abstract: We have developed a clean, simple and efficient method for the synthesis of spiro compounds by three-component reaction of isatins (=1H-indole-2,3-diones) or acenaphthylene-1,2-dione, 1,3-diphenyl-1H-pyrazoles-5-amines, and tetronic acid (=furan-2,4-(3H,5H)-dione or 2-hydroxy-1,4-naphthoquinone in the presence of a catalytic amount of L-proline in aqueous media. The advantages of this procedure are mild reaction conditions, high yields of products, operational simplicity, and easy workup procedures employed.

Journal ArticleDOI
TL;DR: One new anthracene derivative, juglanthracenoside A (1), along with two new anthraquinones (Juglanthraqui-none A (2) and juglanthsraquinone B (3) along with 9,10-dioxoanthracene-2-carboxylic acid (4) have been isolated from the stembark of Juglans mandshurica as mentioned in this paper.
Abstract: ) Institute of Genetics and Cytology, Northeast Normal University, Renmin Street 5268,ChangChun 130024, P. R. ChinaOne new anthracene derivative, juglanthracenoside A (1), two new anthraquinones, juglanthraqui-none A (2) and juglanthraquinone B (3), along with a new naturally occurring anthraquinone, 9,10-dihydro-4,8-dihydroxy-9,10-dioxoanthracene-2-carboxylic acid (4), have been isolated from the stembark of Juglans mandshurica. Their structures were established by detailed spectroscopic analysis andcomparison of the NMR data with those of related compounds. Compound 1 displayed noticeableantioxidantactivityinboth1,1-diphenyl-2-picrylhydrazyl(DPPH)and2,2’-azinobis(3-ethylbenzothiazo-line-6-sulfonic acid) (ABTS) free radical-scavenging assays, while compound 4 showed strongcytotoxicity against HepG2, SGC7901, HCT-8, and A549 cell lines in vitro.

Journal ArticleDOI
TL;DR: In this article, a sequential one-pot four-component reaction for the efficient synthesis of novel 2′-aminospiro[11H-indeno[1,2-b]quinoxaline-11,4′-[4H]pyran] derivatives in the presence of AcONH4 as a neutral, inexpensive, and dually activating catalyst is described.
Abstract: A sequential one-pot four-component reaction for the efficient synthesis of novel 2′-aminospiro[11H-indeno[1,2-b]quinoxaline-11,4′-[4H]pyran] derivatives 5 in the presence of AcONH4 as a neutral, inexpensive, and dually activating catalyst is described (Scheme 1). The syntheses are achieved by reacting ninhydrin (1) with benzene-1,2-diamines 2 to give indenoquinoxalines, which are trapped in situ by malono derivatives 2 and various α-methylenecarbonyl compounds 4 through cyclization, providing the multifunctionalized 2′-aminospiro[11H-indeno[1,2-b]quinoxaline-11,4′-[4H]pyran] analogs 5. This chemistry provides an efficient and promising synthetic way of proceeding for the diversity-oriented construction of the spiro[indenoquinoxalino-pyran] skeleton.

Journal ArticleDOI
TL;DR: In this paper, the first report of one-pot synthesis of 2-amino-4H-1-benzopyran-4-ylphosphonic acid dimethyl esters was given.
Abstract: Several (2-amino-4H-1-benzopyran-4-yl)phosphonates were efficiently synthesized by employing a multicomponent protocol involving a salicylaldehyde, malononitrile or ethyl cyanoacetate, and a trialkyl phosphite in polyethylene glycol The latter could be recovered and re-used No additional solvent or catalyst was required To the best of our knowledge, this is the first report of the one-pot preparation of (2-amino-4H-1-benzopyran-4-yl)phosphonic acid dimethyl esters

Journal ArticleDOI
TL;DR: In this article, a combination of liquid/liquid extraction and HPLC analysis of a MeOH extract from Haberlea rhodopensis was used to identify new flavone C-glycosides, including myconoside and paucifloside.
Abstract: Phytochemical profiling of a MeOH extract from Haberlea rhodopensis by a combination of liquid/liquid extraction, and preparative and semi-preparative HPLC afforded three new flavone C-glycosides, hispidulin-8-C-(2″-O-syringoyl)-β-glucopyranoside (3), hispidulin 8-C-(6-O-acetyl-β-glucopyranoside) (4), and hispidulin 8-C-(6-O-acetyl-2-O-syringoyl-β-glucopyranoside) (5), along with two known phenolic glycosides, myconoside (1) and paucifloside (2). The structures were established by extensive spectroscopic analyses including 1D- and 2D-NMR (COSY, HSQC, and HMBC), and HR-ESI-TOF-MS, and by comparison with published data.

Journal ArticleDOI
TL;DR: Three new mycosporine-like amino acids, aplysiapalythines A, B, and C (1, 2, and 3, resp.) were isolated from opaline, a glandular component of the defensive ink secretion of sea hares collected from waters off southern California, and the structure is determined by mass spectrometry and NMR data.
Abstract: Three new mycosporine-like amino acids (MAAs), aplysiapalythines A, B, and C (1, 2, and 3, resp.) were isolated from opaline, a glandular component of the defensive ink secretion of sea hares (Aplysia californica) collected from waters off southern California. Here, we report the structure of these MAAs determined by mass spectrometry and NMR data. These new MAAs are structurally related to two known MAAs that are also present in sea hare opaline, i.e., asterina 330 (4) and palythine (5), and for which we also provide detailed data here for comparison. The fact that three of the five MAAs that we identified from sea hare opaline are novel molecules is interesting given that this represents a relatively large addition to the current list of known MAAs. This is likely because most researchers have identified MAAs through HPLC with UV detection, which is imprecise given similarities in UV spectra for different MAAs. Our findings suggest that there is much greater diversity of MAAs than is currently known. Results published elsewhere show that 1, 2, and 4 are alarm cues for conspecific sea hares at natural concentrations, but 3 and 5 are not.

Journal ArticleDOI
TL;DR: Two new 5-methoxyfuran-3(2H)-one derivatives, huaspenone A and B, together with four known ones, including aspertetronin A, were isolated from the cultures of an endophytic fungus Aspergillus sp.
Abstract: Two new 5-methoxyfuran-3(2H)-one derivatives, huaspenone A (1) and B (2), together with four known ones, i.e., aspertetronin A (3), aspertetronin B (4), gregatin E (5), and penicilliol A (6), were isolated from the cultures of an endophytic fungus Aspergillus sp. XW-12, derived from the stems of Huperzia serrata. The structures of the new isolates were established by detailed interpretation of the 1D- and 2D-NMR and HR-ESI-MS data.

Journal ArticleDOI
TL;DR: In this article, the stereochemical course of (diethylamino)sulfur trifluoride (DAST) reactions with N,N-dibenzyl-2,amino-3-hydroxy and 3-amino 2,2,hydroxy carboxylic acid esters is discussed.
Abstract: The preparation of (2S,3S)- and (2R,3S)-2-fluoro and of (3S)-2,2-difluoro-3-amino carboxylic acid derivatives, 1–3, from alanine, valine, leucine, threonine, and β3h-alanine (Schemes 1 and 2, Table) is described. The stereochemical course of (diethylamino)sulfur trifluoride (DAST) reactions with N,N-dibenzyl-2-amino-3-hydroxy and 3-amino-2-hydroxy carboxylic acid esters is discussed (Fig. 1). The fluoro-β-amino acid residues have been incorporated into pyrimidinones (11–13; Fig. 2) and into cyclic β-tri- and β-tetrapeptides 17–19 and 21–23 (Scheme 3) with rigid skeletons, so that reliable structural data (bond lengths, bond angles, and Karplus parameters) can be obtained. β-Hexapeptides Boc[(2S)-β3hXaa(αF)]6OBn and Boc[β3hXaa(α,αF2)]6-OBn, 24–26, with the side chains of Ala, Val, and Leu, have been synthesized (Scheme 4), and their CD spectra (Fig. 3) are discussed. Most compounds and many intermediates are fully characterized by IR- and 1H-, 13C- and 19F-NMR spectroscopy, by MS spectrometry, and by elemental analyses, [α]D and melting-point values.

Journal ArticleDOI
TL;DR: In this paper, the reactions of (−)-cis-verbenol epoxide with a number of aromatic aldehydes containing OH and/or MeO groups in the presence of montmorillonite K10 clay have been studied.
Abstract: The reactions of (−)-cis-verbenol epoxide with a number of aromatic aldehydes containing OH and/or MeO groups in the presence of montmorillonite K10 clay have been studied. Several new O-containing heterocyclic compounds with different frameworks, including compounds with a previously unknown octahydro-2H-4,6-(epoxymethano)chromene framework, have been synthesized. Introduction of one donor substituent in the benzaldehyde molecule led to a decrease in the total yield of intermolecular by formed products, while the introduction of two and more substituents led to an increase in the yield of these products.

Journal ArticleDOI
TL;DR: Jatrophodione A (1), a new diterpene with four rings, together with nine known compounds, caniojane (2), jatropholone A (3), Jatrogolone B (4), JATrogrossidione (5), 2-epijatrogrossIDione (6), heudelotinone (7), gossweilone (8), (3 alpha)-3-hydroxy-ent-pimara-8(14), 15-dien-12-one (
Abstract: Jatrophodione A (1), a new diterpene with four rings, together with nine known compounds, caniojane (2), jatropholone A (3), jatropholone B (4), jatrogrossidione (5), 2-epijatrogrossidione (6), heudelotinone (7), gossweilone (8), (3 alpha)-3-hydroxy-ent-pimara-8(14), 15-dien-12-one (9), and 12-hydroxy-13-methylpodocarpa-8,11,13-trien-3-one (10), was isolated from the aerial parts of Jatropha curcas. Compounds 5, 6, 9, and 10 were found for the first time in this plant. Their structures were established by spectroscopic analysis, including 2D-NMR spectroscopic techniques. Cytotoxicities of compounds 1, 2, 7, 8, and 9 were tested on the three cancer cell lines A549, Hela, and SMMC-7721. Results showed that 7 exhibited cytotoxicity against SMMC-7721 with an IC(50) value of 21.68 mu m, whereas 7 and 8 were active against A549 with the IC(50) values of 16.04 and 20.47 mu m, and against Hela with the IC(50) values of 10.67 and 22.83 mu m, respectively.

Journal ArticleDOI
TL;DR: In this paper, six polyhydroxypregnane glycosides, namely cynotophyllosides A-F (1−6), together with five known steroids, were isolated from the roots of Cynanchum otophyllum.
Abstract: Six new polyhydroxypregnane glycosides, namely cynotophyllosides A–F (1–6), together with five known steroids, were isolated from the roots of Cynanchum otophyllum. Their structures were elucidated by extensive spectroscopic methods (especially 2D-NMR techniques) and acid-catalyzed hydrolysis. Furthermore, high field 1D- and 2D-NMR experiments were employed to elucidate the structure of 8 previously deduced only on the basis of LC/MS data.

Journal ArticleDOI
TL;DR: A remote 4J(F,H) coupling (FC(α)C(O)NH) of up to 4.2 Hz in α-fluoro amides with antiperiplanar arrangement of the CF and the CO bonds confirms that previous NMR determinations, using the XPLOR-NIH procedure, of the secondary structures of β-peptides containing β3hAla(αF) and αF2) residues were correct.
Abstract: A remote 4J(F,H) coupling (FC(α)C(O)NH) of up to 4.2 Hz in α-fluoro amides with antiperiplanar arrangement of the CF and the CO bonds (dihedral angle FCCO ca. 180°) confirms that previous NMR determinations, using the XPLOR-NIH procedure, of the secondary structures of β-peptides containing β3hAla(αF) and β3hAla(αF2) residues were correct. In contrast, molecular-dynamics (MD) simulations, using the GROMOS program with the 45A3 force field, led to an incorrect conclusion about the relative stability of secondary structures of these β-peptides. The problems encountered in NMR analyses and computations of the structures of backbone-F-substituted peptides are briefly discussed.

Journal ArticleDOI
TL;DR: Three triterpenoid derivatives, named (15α)-15-hydroxysoyasapogenol B (1), (7β, 15α)-7,15-dihydroxy SOYASPAGNOL B (2), and (7 β, 7, 29)-dihyldihydroxysapogenols B (3), were isolated from cultures of the plant endophytic fungus Pestalotiopsis clavispora and their structures were elucidated by extensive spectroscopic analysis and X-ray crystallography.
Abstract: Three new triterpenoid derivatives, named (15α)-15-hydroxysoyasapogenol B (1), (7β,15α)-7,15-dihydroxysoyasapogenol B (2), and (7β)-7,29-dihydroxysoyasapogenol B (3), were isolated from cultures of the plant endophytic fungus Pestalotiopsis clavispora. Their structures and relative configurations were elucidated by extensive spectroscopic analysis and X-ray crystallography.

Journal ArticleDOI
TL;DR: In this article, the synthesis of two new flavin substituted calix[4]arene derivatives, 9 and 10, was described and characterized by a combination of FT-IR and 1H-NMR spectroscopy, and elemental analysis techniques.
Abstract: The synthesis of two new flavin substituted calix[4]arene derivatives, 9 and 10, is described. The first flavin substituted calix[4]arene derivative 9 was synthesized by the reaction of 3-methylalloxazine (5) with 25,27-bis(3-bromopropoxy)-26,28-dihydroxy-5,11,17,23-tetra(tert-butyl)calix[4]arene (4) in high yield (92%). The other derivative 10 was prepared from 3-methylalloxazine-1-acetic acid (7) and 25,27-bis(3-cyanopropoxy)calix[4]arene (3). All new compounds were characterized by a combination of FT-IR and 1H-NMR spectroscopy, and elemental-analysis techniques.