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1.
Aspergiolide A, a novel antitumor compound, was produced by a marine-derived filamentous fungus Aspergillus glaucus. The biosynthesis of it was unambiguously determined by feeding experiments using [l-13C]sodium acetate, [2-13C]sodium acetate, and [1,2-13C2]sodium acetate precursors followed by 13C NMR spectroscopic investigation of the isolated products. Analysis of the patterns of 13C-enrichment revealed that all 25 carbon atoms in skeleton of aspergiolide A were derived from labeled acetate. And among them, 12 carbon atoms were labeled from the carboxylic group of acetate, while the other 13 carbon atoms were labeled from the methylic group of acetate. Besides, the labeling pattern of [1,2-13C2]sodium acetate feeding experiment demonstrated that 12 intact acetate units were incorporated in aspergiolide A by polyketide pathway. 相似文献
2.
The biotransformation of botrydienediol (6) labelled with deuterium on carbons C-10 and C-15 has been studied. This has led to modification of some previous assumptions about the biodegradative route of botrydial. The [10-2H,15-2H]-botry-1(9)-4-diendiol (12) was transformed into dehydrobotrydienediol derivatives 13-15 but it was not incorporated into secobotryane skeleton (7). In addition, three new sesquiterpenoids have been isolated, which shed further light on the secondary metabolites of Botrytis cinerea. From the point of view of persistence of these toxins in the food chain, the easy biotransformation and different biodegradative routes of botrydial (1), seem to indicate that the toxin may not persist in the plant for a long time as it will be metabolized by the fungi and the plant. 相似文献
3.
Incednine was isolated from Streptomyces sp. ML694-90F3 as an inhibitor of anti-apoptotic function of Bcl-2/Bcl-xL oncoproteins. The structure of incednine is quite unique with a characteristic 24-membered macrocyclic lactam aglycone and two unusual aminosugars. To understand its biosynthetic pathway, the incorporation studies were carried out with [1-13C]acetate, [1,2-13C2]acetate, [1-13C]propionate, l-[13C5,15N]glutamate, [1,2,3-13C3]glycerol, d-[6,6-2H2]glucose, and l-[CH3-13C]methionine. As a result, acetate, propionate, and glycerol were well incorporated into the elongation units of the macrolactam moiety, which indicates that its basic skeleton could be constructed by standard polyketide synthase, whereas all atoms of the starter unit were labeled by [13C5,15N]glutamate suggesting that glutamate is somehow decarboxylated and rearranged into 3-aminobutyrate as the unique starter unit. The origins of the sugar moieties and methyl groups were also clarified. Based on the incorporation pattern, a plausible biosynthetic pathway for incednine is proposed. 相似文献
4.
Arif Baran 《Tetrahedron》2004,60(4):861-866
The actions of AcX (X=Br, Cl) on 7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetates and a transoid-epoxide prepared from the acetonide of cyclohexa-3,5-diene-cis-1,2-diol were studied. H2SO4-catalyzed cleavage of exo-cis-7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetate with AcCl gave (1α,2α,3α,6β)-6-chloro-4-cyclohexene-1,2,3-triol triacetate, from which the corresponding chloroconduritol was obtained by trans-esterification (MeOH/HCl). A similar reaction of the exo-diacetate with AcBr in the presence of H2SO4 resulted in bromine addition. The formation of bromine from the reaction of AcBr and H2SO4 was observed by independent experiments. H2SO4-catalyzed reaction of endo-cis-7-oxa-bicyclo[2.2.1]hept-5-ene-2,3-diol diacetate with AcX (X=Br, Cl) gave (1α,2α,3β,6β)-6-halo-4-cyclohexene-1,2,3-triol triacetates. The reaction of the transoid-epoxide with AcX (X=Br, Cl) with no catalyst gave also (1α,2α,3β,6β)-6-halo-4-cyclohexene-1,2,3-triol triacetates. 相似文献
5.
Kittisak SriphaDarius Paul Zlotos 《Tetrahedron》2003,59(3):391-394
In search of new lead structures for potent allosteric enhancers of antagonist binding to muscarinic M2 receptors, the first representative of a novel heterocyclic ring system, 6,7,14,15-tetrahydro[1,5]diazocino[1,2-a:6,5-a′]diindole, has been synthesized. The new pentacyclic ring skeleton is obtained from [3-(2-dibenzylaminoethyl)indol-2-yl]-acetic acid methyl ester in three steps. 相似文献
6.
Yuta Fujita 《Tetrahedron letters》2005,46(35):5885-5888
Incorporation of labeled acetate and l-serine into PF1140 in Eupenicillium sp. indicated that the skeleton of PF1140 is derived from five acetates and a l-serine. Upon administration of [1,3-13C2]glycerol, a precursor of biotransformation into l-[1,3-13C2]serine, the isotopic labels became contiguous in the resultant 2-pyridone of PF1140. Based on the feeding experiments, a novel and potentially general biosynthetic pathway for a 2-pyridone framework has been proposed, in which an acyl tetramic acid precursor could be converted via a ring expansion with loss of the hydroxyl group. 相似文献
7.
The labeling pattern obtained from incorporation of a mixture of sodium [1-13C]- and [s-13C]acetates has confirmed the irregular derivation of the benz[α]anthraquinone skeleton of the angucycline antibiotic PD 116198. Subsequent incorporation of sodium [1-13C, 18O2]-, and [1-13C, 2-2H3]acetates and of 18O2 have revealed the origins of the hydrogen and oxygen atoms of the antibiotic. The possibility of a “two-chain” biosynthesis was tested by feeding 2H-labeled orsellinates; however, no incorporation was detected. PD 116198 seems most plausibly derived by rearrangement of an initially-formed linear tetracyclic intermediate. 相似文献
8.
Katsumi Iida 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(3):1819-1827
The biosynthetic pathways leading to δ-aminolevulinic acid (ALA) from the Shemin precursor glycine via the C5 pathway in Arthrobacter hyalinus were quantitatively evaluated by means of feeding experiments with [2-13C]glycine, sodium [1-13C]acetate, and sodium [2-13C]acetate, followed by analysis of the labeling patterns of coproporphyrinogen III (Copro’gen III) (biosynthesized from ALA) using 13C NMR spectroscopy. Two biosynthetic pathways leading to ALA from glycine via the C5 pathway were identified: i.e., transformation of glycine to l-serine catalyzed by glycine hydroxymethyltransferase, and glycine synthase-catalyzed catabolism of glycine to N 5,N 10-methylene-tetrahydrofolic acid (THF), which reacts with another molecule of glycine to afford l-serine. l-Serine is transformed to acetyl-CoA via pyruvic acid. Acetyl-CoA enters the tricarboxylic acid cycle, affording 2-oxoglutaric acid, which in turn is transformed to l-glutamic acid. The l-glutamic acid enters the C5 pathway, affording ALA in A. hyalinus. A 13C NMR spectroscopic comparison of the labeling patterns of Copro’gen III obtained after feeding of [2-13C]glycine, sodium [1-13C]acetate, and sodium [2-13C]acetate showed that [2-13C]glycine transformation and [2-13C]glycine catabolism in A. hyalinus proceed in the ratio of 52 and 48 %. The reaction of [2-13C]glycine and N 5,N 10-methylene-THF, that of glycine and N 5,N 10-[methylene-13C]methylene-THF generated from the [2-13C]glycine catabolism, and that of [2-13C]glycine and N 5,N 10-[methylene-13C]methylene-THF transformed the fed [2-13C]glycine to [1-13C]acetyl-CoA, [2-13C]acetyl-CoA, and [1,2-13C2]acetyl-CoA in the ratios of 42, 37, and 21 %, respectively. These labeled acetyl-CoAs were then incorporated into ALA. Our results provide a quantitative picture of the pathways of biosynthetic transformation to ALA from glycine in A. hyalinus. 相似文献
9.
Maciej PisklakFranciszek Herold Romana Anulewicz-OstrowskaIwona Wawer 《Journal of Molecular Structure》2002,605(1):85-92
13C cross-polarisation magic angle spinning NMR data have been reported for four derivatives of 4-aryl-octahydro-pyrido[1,2-c]pyrimidine-1,3-dione and the X-ray diffraction data for two (with 2′-Me and 2′-OMe). The crystal structures show the presence of centrosymmetric cyclic dimers with intermolecular C1O?H-N or C3O?H-N hydrogen bonds, the configuration at the chiral centres (C4 and C4a) was determined as RR (SS). The twisting of aromatic ring at C4 with respect to the pyrido[1,2-c]pyrimidine skeleton is about 68-109°. 相似文献
10.
Biosynthetic feeding studies of [1-13C], [2-13C], and [1,2-13C2]-labeled sodium acetates into 5-epihydroxyvertinolide, a new sorbicillinoid, gives an incorporation pattern that proves the γ-lactone ring formation associated with a ring cleavage reaction of the precursor, a potential intermediate of sorbicillinol biosynthesis. 相似文献
11.
The stereochemistry of syn and anti-forms of bridged bicyclo[3.n.1]-2-ene, tricyclo[7.n.1.0]-2-ene (n=1-3) and bicyclo[4.3.1]dec-7-ene derivatives can be assigned from the 13C chemical shift difference of the double bond. Both syn-9-R-bicyclo[3.3.1]non-2-enes and syn-13-R-tricyclo[7.3.1.02,7]tridec-2(7)-enes have a large shielding difference between sp2 carbons, while the corresponding anti-forms have a smaller one. In contrast, 8-R-bicyclo[3.2.1]oct-2-enes and 12-R-tricyclo[7.2.1.02,7]dodec-2(7)-enes have an inverse correlation. The reason of this specificity is the influence of the γ-gauche effect on the chemical shift of C(2) atom. The GIAO theory has been applied to investigate the 13C chemical shifts. The conformational equilibrium in the formamide group of 13-formylamino-tricyclo[7.3.1.02,7]tridec-2(7)-enes has been studied. 相似文献
12.
The Stille cross-coupling reaction of [1-11C]acetyl chloride with tributylphenylstannane leading to [carbonyl-11C]acetophenone was studied with the goal of developing a new 11C-labeling method for positron emission tomography tracer synthesis. The coupled product [carbonyl-11C]acetophenone was synthesized using the Pd2(dba)3/P(MeNCH2CH2)3N·HCl system with a 60-61% radiochemical conversion from [1-11C]acetyl chloride (decay-corrected, n = 3). 相似文献
13.
Gabriele Albertin Stefano Antoniutti Stefano Paganelli 《Journal of organometallic chemistry》2010,695(18):2142-169
p-Cymene complexes MCl2(η6-p-cymene)L [M = Ru, Os; L = P(OEt)3, PPh(OEt)2, (CH3)3CNC] were prepared by allowing [MCl(μ-Cl)(η6-p-cymene)]2 to react with phosphites or tert-butyl isocyanide. Treatment of MCl2(η6-p-cymene)L complexes with 1,3-ArNNN(H)Ar triazene and an excess of NEt3 gave the cationic triazenide derivatives [M(η2-1,3-ArNNNAr)(η6-p-cymene)L]BPh4 (Ar = Ph, p-tolyl). Neutral triazenide complexes MCl(η2-1,3-ArNNNAr)(η6-p-cymene) (M = Ru, Os) were also prepared by allowing [MCl(μ-Cl)(η6-p-cymene)]2 to react with 1,3-diaryltriazene in the presence of triethylamine. p-Cymene complexes MCl2(η6-p-cymene)L reacted with equimolar amounts of 1,3-ArNNN(H)Ar triazene to give both triazenide complexes [M(η2-1,3-ArNNNAr)(η6-p-cymene)L]BPh4 and amine derivatives [MCl(ArNH2)(η6-p-cymene)L]BPh4. A reaction path for the formation of the amine complex is also reported. The complexes were characterised by spectroscopy and X-ray crystallography of RuCl2(η6-p-cymene)[PPh(OEt)2] and [Ru(η2-1,3-p-tolyl-NNN-p-tolyl)(η6-p-cymene){CNC(CH3)3}]BPh4. Selected triazenide complexes were studied as catalysts in the hydrogenation of 2-cyclohexen-1-one and cinnamaldehyde. 相似文献
14.
Biosynthetic origin of macrolactam polyketide antibiotic cremimycin was investigated by feeding experiments with [1-13C]acetate, [1,2-13C2]acetate, [1-13C]propionate, succinate-d4, and d-[6,6-2H2]glucose. NMR analysis of the resultant isotope-enriched cremimycins showed distinctive incorporation patterns, which suggested that the aglycon of cremimycin was constructed from two propionates and eleven acetates. Thus, 3-oxononanoate was proposed as a potential polyketide intermediate, that is, aminated to be the unique nitrogen-containing moiety of cremymicin. Further, characteristic propionate biosynthetic pathway in the cremimycin-producing strain was also described. 相似文献
15.
In search of new lead structures for potent allosteric enhancers of antagonist binding to muscarinic M2 receptors, a novel heterocyclic ring system, 6,7,14,15-tetrahydro-15aH-azocino[1,2-a:6,5-b′]diindole, has been synthesized. The new ring skeleton was obtained from indol-2-yl-acetic acid in three steps. 相似文献
16.
Three new triterpenoidal glucosides, justiciosides E, F and G, were isolated from the aerial portion of Justicia betonica. Their structures were established through chemical and spectroscopic analyses, and showed an unusual A-nor-B-homo oleanan-12-ene skeleton type for the aglycone moiety as A-nor-B-homo-oleanan-10,12-diene-3β,11α,28-triol 28-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside, A-nor-B-homo-oleanan-10,12-diene-3β,11α,28-triol 28-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside, and 11α-methoxy-A-nor-B-homo-oleanan-10,12-diene-3β,11α,28-triol 28-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside, respectively. 相似文献
17.
Robert ?ysek 《Tetrahedron》2007,63(28):6558-6572
Starting from (±)-7-oxanorbornenone ((±)-14), (±)-(1RS,2RS,3SR,6SR)-6-azidocyclohex-4-en-1,2,3-triol ((±)-24) and (±)-(1RS,2RS,3SR,6RS)-6-azidocyclohex-4-en-1,2,3-triol ((±)-26) were obtained. Epoxidation of the latter cyclohexene derivative gave two epoxides (±)-30 and (±)-31 that were converted into (±)-conduramine F-1 epoxides (±)-10 and (±)-11 and N-substituted derivatives (±)-12 and (±)-13. Compound (±)-(1RS,2SR,3RS,4SR,5RS,6SR)-5-({[4-(trifluoromethyl)phenyl]methyl}amino)-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-12c) is a good, non-competitive inhibitor of β-xylosidase from Aspergillus niger (Ki=2.2 μM), and (±)-(1RS,2RS,3SR,4RS,5SR,6SR)-5-{[(biphenyl-4-yl)methyl]amino}-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-13d) is a good inhibitor of α-glucosidase from brewer's yeast (Ki=2.8 μM, non-competitive). 相似文献
18.
Yasuyo SekiyamaNadaraj Palaniappan Kevin A ReynoldsHiroyuki Osada 《Tetrahedron》2003,59(38):7465-7471
Phoslactomycins (PLMs) A-F, produced by actinomycetes are polyketide-type antibiotics derived from a hydroxycyclohexanecarboxylic acid or a cyclohexanecarboxylic acid starter unit. Feeding experiments with [2-13C]shikimic acid indicated that the C-18 carbon of PLMs comes from C-5 of shikimate. Further feeding studies of cis and trans-3-hydroxy[7-13C]cyclohexanecarboxylic acid, [7-13C]- and [2H11]cyclohexanecarboxylic acid have suggested that the starter unit in the PLM biosynthesis is not cis-3-hydroxycyclohexanecarboxylate but cyclohexanecarboxylate and that PLM-B is produced initially, and subsequently converted to other analogs by hydroxylation and acylation. 相似文献
19.
The origin of the carbon skeleton of verrucarin E (1) from acetate as precursor is confirmed. Incorporation studies with [1,2-13C]-acetate have demonstrated that two acetoacetate units couple together as shown in pattern A (Scheme 2) and not as in B . Analysis of the deuterium distribution in both verrucarin E (1) isolated after the incorporation of [2-13C,2-2H3]-acetate and in sodium acetate obtained after Kuhn-Roth oxidation of the metabolite demonstrated that C(7) is derived from the starter unit of one of the acetoacetate moieties. The deuterium exchange in verrucarin E (1) occurring during fermentation was investigated. 相似文献
20.
A series of novel N-benzylcarboxamide derivatives of bicyclic compounds, 3,4-dihydropyrido[3,2-f][1,4]oxazepin-5(2H)-one and 2,3,4,5-tetrahydro-6H-pyrido[2,3-b][1,5]oxazocin-6-one, were synthesized by cyclization of N-benzyl-2-chloro-N-(2-hydroxyethyl)- [and -(3-hydroxypropyl)-] nicotinamides, respectively. Atropisomerism was observed in 5-[3,5-bis(trifluoromethyl)benzyl]-7-phenyl-2,3,4,5-tetrahydro-6H-pyrido[2,3-b][1,5]oxazocin-6-ones due to steric hindrance of the carboxamide moiety and restriction of its rotation. Cyclization of N-[3,5-bis(trifluoromethyl)benzyl]-2-chloro-N-[(2S)-3-hydroxy-2-methylpropyl]-5-methyl-4-phenylnicotinamide gave (3S)-5-[3,5-bis(trifluoromethyl)benzyl]-3,8-dimethyl-7-phenyl-2,3,4,5-tetrahydro-6H-pyrido[2,3b][1,5]oxazocin-6-one, which exists predominantly in the thermodynamically stable aR-conformer in CDCl3. This compound showed excellent NK1-antagonistic activity with IC50 value (in vitro inhibition of [125I]-Bolton-Hunter-substance P binding in human IM-9 cells) of 0.47 nM, which is ca. 200-fold more potent than that of its enantiomer, indicating that the atropisomer chirality affects NK1-receptor recognition. 相似文献