Identification of a new antifungal oligoacetal derivative produced by Streptomyces toxytricini against Candida albicans

Thirty actinomycete isolates were isolated from soil and tested against Candida albicans in vitro. The active isolate was identified by 16s-rRNA gene sequencing method as Streptomyces toxytricini. The antifungal compound was extracted with ethyl acetate followed by diethyl ether. Both HPLC and GC–MS analysis confirmed presence of one pure compound in the diethyl ether extract. The compound is a yellow liquid has a maximum absorbance at 240 nm in methanol. The chemical structure was elucidated by 1D and 2D-NMR and IR analyses. The elucidated molecular formula was C₃₆H₅₄O₁₄. The compound is a polyacetal tricyclononane derivative, composed of a tricyclononane ring attached from the carbon atom number four with an oligo-acetal chain (six acetal groups in chain) and from the carbon atom number seven with a methoxy carbonyl benzene-1,3-dicarboxylic acid. The purposed name is: 4- {[tricycle(3.2.1.1^1,3)non-8-yl] methoxy carbonyl benzene-1,3-dicarboxylic acid} (2,4,5,6,7,8,9 heptaoxa, 3-ethoxy, 5,6,7,9-tetramethyl unidecane).     

Lewis Acidity of Carbon in Activated Carbonyl Group vs. B(C6F5)3 for Metal-Free Catalysis of Hydrogenation of Carbonyl Compounds

In this work, using DFT calculations, we investigated Lewis acidities of carbon (in activated carbonyl group) in comparison to the B(C₆F₅)₃ in combination with dioxane as the Lewis base (LB) for metal-free catalysis of heterolytic H₂ splitting and hydrogenation of carbonyl compounds. We found that in case of carbon as the Lewis acid (LA) the reaction is controlled by frontier molecular orbital interactions between the H₂ and LA-LB fragments at shorter distances. The steric effects can be reduced by electrophilic substitutions on the carbonyl carbon. Synergic combination between stronger orbital interactions and reduced steric effects can lower the barrier of the H₂ splitting below 10 kcal/mol. With the B(C₆F₅)₃, the H₂ splitting is controlled by electrostatic interactions, which cause to form an early transition state. An advantage of employing Lewis acidity of the activated carbonyl carbon for hydrogenation is that the hydride-type attack and hydrogenation of the C=O bond occur in a single step throughout H₂ splitting. Hence, stronger Lewis acidity of the C(C=O) reinforces hydrogenation without prohibition of the hydride delivery.     

纳米铝粉促进羰基化合物水相烯丙基化反应

氮气保护条件下,纳米铝在0.1 N NH₄Cl溶液中,能有效地促进羰基化合物与烯丙基溴进行Barbier-Grignard型烯丙基化反应,得到相应高烯丙醇。芳香族醛或酮的烯丙基化产率较高,而脂肪族羰基化合物反应产率低,反应产率受羰基空间位阻影响大,在同样条件下,邻羟基羰基化合物烯丙基化产物主要是赤式-邻二醇。     

Effects of substitution on nitrogen on barriers to rotation of amides. 2—Evaluation of the importance of resonance effects

Analogs of N-acetyl- and N-benzoyl-azacyclohex-2-enes having an oxygen atom, a methylene-d₂ group or a carbonyl group in place of the C-4 methylene group have been synthesized. The amide rotational barriers in these compounds have been measured by the total line-shape analysis of variable-temperature ¹H NMR spectra. The free energies of activation for both the N-acetyl and N-benzoyl series decrease in the sequence O?CD₂ > C?O. The barriers for the first two compounds in each series are similar to those of the corresponding saturated analogs, a result which confirms recent reports that the long accepted barrier-decreasing effect of an α-olefinic substituent on nitrogen is counteracted. Evidence is presented that resonance stabilization of the rotational transition state in the unsaturated compounds still obtains. It is suggested that the introduction of an α-olefinic substituent on nitrogen has a negligible effect on the amide rotational barriers in the cases of the oxygen and methylene-d₂ analogs, since any increase in the stabilization of the transition state by resonance is offset by the accompanying decrease in the sp³ character of the nitrogen atom. In cases in which a substituent on the olefinic group can interact directly with the lone pair on nitrogen, for example in the carbonyl analogs, then the resonance stabilization of the transition state is dominant.     

Acetone in its lowest excited triplet state: an isotope dependent ODMR study

The lowest excited triplet state T₁ of acetone-h₆ and acetone-d₆ was investigated with a pulsed dye laser equipped Optical Detection of Magnetic Resonance spectrometer. The results obtained for this prototype aliphatic carbonyl compound are discussed with reference to a recent ab initio calculation on formaldehyde. The peculiarities of the acetone T₁ are largely determined by its distinct non-planar geometry: Our data indicate that the carbonyl group is rotated out of the plane defined by the three C-atoms, and the distortion angle is found to be appoximately 38°C, similar to the formaldehyde value. This is a central result of our investigation: All of the observed zero-field splitting parameters, ODMR linewidths, kinetic data, and the deuterium effects can be satisfactorily rationalized with this out-of-plane distortion.     

Carbonyl derivatives of phthalocyaninatoiron(II), especially those containing group VI axial donor atoms. Crystal and molecular structure of carbonyl(N,N-dimethylformamide)phthalocyaninatoiron(II) and mössbauer studies of some of the products

The carbonyl adduct of phthalocyaninatoiron(II), FePc, with N,N-dimethylformamide (DMF) as axial ligand, FePc(CO)DMF, was prepared by the reaction of iron carbonyls, Fe(CO)₅ or Fe₂(CO)₉, with o-phthaalonitrile in DMF as solvent. Several carbonyl adducts of FePc of general formula FePc (CO)L are reported, with L being a ligand with oxygen, sulphur and nitrogen donor atoms (L = tetrahydrofuran, H₂O, CH₃OH, dimethylsulphoxide, tetrahydrothiophene, ammonia, n-propylamine, diethylamine, triethylamine). The crystal and molecular structure of FePc(CO)DMF·DMF was investigaed by X-ray diffraction methods. The compound has a monoclinic unit cell and space group P2₁/n, a 9.86(1), b 17.35(3), c 19.79(4) », β 87.9(2)°, Z = 4, U 3383 »³, D₃ 1.458 g cm^?3. The iron atom is hexacoordinated to the four inner nitrogen atoms of the macrocyle, to carbon monoxide (Fe—C distance 1.72(2) ») and to DMF (Fe—O distance 2.07(1) »). The extra DMF occupies lattice sites. All of the compounds reported in this paper are substantially diamagnetic. Mössbauer spectra show typical isomer shift parameters for the bis-adducts and for the carbonyl adduct, substantially independent of the nature of the axial ligand. The quadrupole splitting parameter of the carbonyl adducts is strongly affected by the nature of the axial ligand.     

Addition de l'Hexafluoroacétone sur les Acides Carboxyliques—Mise en Évidence par RMN 1H et 19F. Application à l'Analyse d'un Mélange d'Acides

The compound HO? C(CF₃)₂? O₂CR results from nucleophilic addition of a carboxylic acid to the carbonyl group of hexafluoroacetone. I.r. and n.m.r. (¹H, ¹⁹F) spectroscopy have been used to show that the addition is reversible. The addition is favoured by a lowering of the temperature and by the use of acids in which the group R is electron donating. Moreover, the chemical shift of the CF₃ groups (or of the OH group) in the addition product is dependent on the nature of R. Thus, this reversible addition can be used as a method for the analysis of a mixture of carboxylic acids by n.m.r. spectroscopy.     

n→π*-Übergänge in Dicarbonylverbindungen Der Einfluss der n,n- und π*, π*-Wechselwirkung

By CNDO-CI calculations we have found that dicarbonyl compounds exhibit only two n → π* transitions in the visible or near UV. region, instead of four as expected from simpler MO-models. The dominant features of the long-wavelength electronic spectra may be characterized by the relative energy of the two n and the two lowest π* orbitals. In general we distinguish between three cases:

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Biosynthesis of phoslactomycins: cyclohexanecarboxylic acid as the starter unit

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.     

Synthesis and antiemetic activity of 1,2,3,9-tetrahydro-9-methyl-3-(4-substituted-piperazin-1-ylmethyl)-4H-carbazol-4-one derivatives

5-HT₃ receptor antagonists, such as Ondansetron, are used for anti-emesis after chemotherapy, radiotherapy and operations. Some Ondansetron analogs possessing piperazine ring as side chains were synthesized in our lab. Thus, one of the two carbonyl groups of starting material 1,3-cyclohexandione (1) was condensed with phenylhydrazine hydrochloride to form monophenylhydrazone (2). 1,2,3,9-Tetrahydro-4H-carbazol-4-one (3) was prepared from 2 via cyclization and rearranged in the presence of ZnCl₂. Through a methylation reaction, compound 3 was converted to 1,2,3,9-tetrahydro-9-methyl-4H-carbazol-4-one (4). 3-Dimethylaminomethyl substituted compound (5) was synthesized from 4 by a Mannich reaction in glacial acetic acid. Nine novel 1,2,3,9-tetrahydro-9-methyl-3-(4-substituted-piperazin-1-ylmethyl)-4H-carbazol-4-one derivatives (6a–6i) were synthesized through nucleophilic substitution reaction of 5 with piperazines. The structures of all the target compounds were determined by elemental analysis, IR, MS, ¹H NMR and ¹³C NMR spectra. The results of preliminary pharmacological test show that part of the novel compounds have antiemetic activity comparable to that of the control Ondansetron. __________ Translated from Chinese Journal of Organic Chemistry, 2008, 28(2) (in Chinese)     

Bildung siliciumorganischer Verbindungen. 80. Die Si-Metallierung von 1,3,5-Trisilacyclohexanen mit Übergangsmetallkomplexen

Formation of Organosilicon Compounds. 80. Si-Metalation of 1,3,5-Trisilacyclohexanes by Means of Trisition Metal Complexes Several Si-transition metal-substituted 1,3,5-trisilacyclohexanes are reported. l-Bromo-1,3,5-trisilacyclohexane reacts with the metal carbonyl anions W(CO)₅cp^?, Mo(CO)₃cp-, Cr(CO)₃cp^?, Mn(CO)₃^?, Fe(CO)₂cp^?, or Co(CO)_4minus;, resp., yielding monosubstituted derivatives as 6, e. g.(cp = π-cyclopentadienyl). 1,3-Dibromo-1,3,5-trisilacyclohexane forms disubstituted compounds aa 7, e. g., with 2 moles of the metal carbonyl anions Fe(CO)₂cp^?, Mn(CO)₅^? or Co(CO)₄^?. Starting from (H₂c? SiHBr)₃ compound 13 is accessible by reaction with KCo(CO)₄. In the soluted compounds the metal carbonyl groups occupy the equatorial positions in the chair form of the six membered ring. The reaction of 13 with Co₂(CO)₈ yields 17 , whereas 6 preferrably forms 18 . Starting from (H₂C? SiH₂)3 the reaction with Co₂(CO)₂ preferrably yields 19. The reported compounds are crystalline, air – and moisture – sensitive. The reported formulae are assured by analysis, IR, and NMR investigations.     

Wittig-Horner Reaction in Heterogenous Media: V1. An Efficient Synthesis of Alkene-Phosphonates and αL-Hydroxymethyl-α-Vinyl Phosphonate in Water in the Presence of Potassium Carbonate

Among the various ways of carrying out the Wittig-Horner reaction, the application of the two-phase system using 50% aqueous NaOH as base with (or) without a phase-transfer catalyst has been a subject of increasing interest over the past few We have shown^l,4 that the use of less basic heterogenous media, including aqueous K₂C0₃ or KHC0₃ or the same bases in Toluene or THF enabled these reactions to be carried out with high yields even with base sens it i ve carbony I compounds. These react ions, that do not need phase transfer catalyst proceed by displacement of acido-basic equilibria by the coupling of the anion 2 of the phosphonate 1 with the electrophilic carbonyl compound 3.     

Fällung von Pentahalogenochromaten(III) aus wasserfreier Essigsäure

By adding alkali metal or ammonium acetate to solutions of Cr^III acetate in mixtures of acetic acid and acetyl halide, non-solvated alkali metal pentahalochromates(III), Cs₂(CrX₅), and acetic acid monosolvates of pentahalochromates(III) with nitrogen bases as a cation, i.e. (PyH)₂(CrX₅) · CH₃COOH, can be precipitated. Whilst the chlorochromate(III) ion shows a characteristic splitting of its ⁴A_2g—⁴T_2g absorption in acetic acid solution, which indicates C_4v symmetry, this splitting is not observed in all examined remission spectra of pentahalochromates(III) in the solid state. Their crystal structure should therefore be characterized by almost regular octahedral crystal fields of halogen around Cr³⁺ ions and probably by linked (CrX₆) units.     

Sequence Distribution of Poly(methyl acrylate) by Incremental Calculation

The carbonyl signal in the 100 MHz ¹³C NMR spectra of poly(methyl acrylate) (PMA) recorded in benzene-d₆ exhibits configurational sensitivity up to pentads, and the signal of backbone β-CH₂ carbons shows splitting up to configurational hexads with traces of octads. Assignment of the sequences to respective signals was confirmed by computer simulation of both carbonyl and methylene signals applying a method of incremental calculation of chemical shifts of individual sequences and second-order Markov statistics for sequence probabilities.     

Kinetics,mechanism, and products of the reaction of diphenylcarbonyl oxide with carboxylic acids

The kinetics of the reactions of acetic, benzoic, formic, oxalic, malic, tartaric, trifluoroacetic, and hydrochloric acids with diphenylcarbonyl oxide Ph₂COO was studied. The carbonyl oxide Ph₂COO was generated by flash photolysis of diphenyldiazomethane Ph₂CN₂ in solutions of acetonitrile and benzene at 295 K. The apparent rate constants of the reaction range from 4.6·10⁸ for (COOH)₂ in MeCN to 7.5·10⁹ L mol^–1 s^–1 for acetic acid in a benzene solution. The reaction mechanism was proposed, according to which at the first stage the carbonyl oxide is reversibly solvated by the solvent. Then the solvated carbonyl oxide reacts with the acid molecule by the mechanism of insertion at the O—H bond.     

Heterogeneous versus Homogeneous Copper(II) Catalysis in Enantioselective Conjugate‐Addition Reactions of Boron in Water

We have developed Cu^II‐catalyzed enantioselective conjugate‐addition reactions of boron to α,β‐unsaturated carbonyl compounds and α,β,γ,δ‐unsaturated carbonyl compounds in water. In contrast to the previously reported Cu^I catalysis that required organic solvents, chiral Cu^II catalysis was found to proceed efficiently in water. Three catalyst systems have been exploited: cat. 1: Cu(OH)₂ with chiral ligand L1 ; cat. 2: Cu(OH)₂ and acetic acid with ligand L1 ; and cat. 3: Cu(OAc)₂ with ligand L1 . Whereas cat. 1 is a heterogeneous system, cat. 2 and cat. 3 are homogeneous systems. We tested 27 α,β‐unsaturated carbonyl compounds and an α,β‐unsaturated nitrile compound, including acyclic and cyclic α,β‐unsaturated ketones, acyclic and cyclic β,β‐disubstituted enones, acyclic and cyclic α,β‐unsaturated esters (including their β,β‐disubstituted forms), and acyclic α,β‐unsaturated amides (including their β,β‐disubstituted forms). We found that cat. 2 and cat. 3 showed high yields and enantioselectivities for almost all substrates. Notably, no catalysts that can tolerate all of these substrates with high yields and high enantioselectivities have been reported for the conjugate addition of boron. Heterogeneous cat. 1 also gave high yields and enantioselectivities with some substrates and also gave the highest TOF (43 200 h^?1) for an asymmetric conjugate‐addition reaction of boron. In addition, the catalyst systems were also applicable to the conjugate addition of boron to α,β,γ,δ‐unsaturated carbonyl compounds, although such reactions have previously been very limited in the literature, even in organic solvents. 1,4‐Addition products were obtained in high yields and enantioselectivities in the reactions of acyclic α,β,γ,δ‐unsaturated carbonyl compounds with diboron 2 by using cat. 1, cat. 2, or cat. 3. On the other hand, in the reactions of cyclic α,β,γ,δ‐unsaturated carbonyl compounds with compound 2 , whereas 1,4‐addition products were exclusively obtained by using cat. 2 or cat. 3, 1,6‐addition products were exclusively produced by using cat. 1. Similar unique reactivities and selectivities were also shown in the reactions of cyclic trienones. Finally, the reaction mechanisms of these unique conjugate‐addition reactions in water were investigated and we propose stereochemical models that are supported by X‐ray crystallography and MS (ESI) analysis. Although the role of water has not been completely revealed, water is expected to be effective in the activation of a borylcopper(II) intermediate and a protonation event subsequent to the nucleophilic addition step, thereby leading to overwhelmingly high catalytic turnover.     

Stereospecific synthesis of novel methyl-substituted mono- and di-methoxy conduritols

Methyl-monomethoxy conduritol-B and methyl-dimethoxy conduritol-B were synthesized starting from 2-methylbenzo-1,4-quinone. Bromination of 2-methylbenzo-1,4-quinone was followed by the reduction of the carbonyl groups with NaBH₄ to give a dioldibromo compound. Methyl-dimethoxy conduritol-B was synthesized from the reaction of the dioldibromo compound with CH₃ONa, followed by acetylation with Ac₂O-pyridine to obtain methyl-dimethoxy diacetate. On the other hand, acetylation of the methyl-dioldibromo compound followed by reaction with LiOH gave a monoepoxide compound stereoselectively. The reaction of the epoxide with H⁺/Ac₂O afforded the monobromo triacetate. Controlled reaction of monobromo-triacetate with CH₃ONa in MeOH furnished the desired new methyl-monomethoxy conduritol-B. The structures of all synthesized compounds were characterized by spectroscopic methods.     

Preparation and mössbauer studies of tetraaquabis[maleato(1-)]-iron(II)

Summary Tetraaquabis[maleato(1-)]iron(II), Fe(C₄H₃O₄)₂ · 4H₂O has been synthesised. The compound is monomeric and is isomorphous with the manganese(II) analogue. The temperature dependence of quadrupole splitting and optical spectral data giveca. 10000 cm^–1,ca. 650 cm^–1,ca. 190 cm^–1 andca. 1400 cm^–1 for the 10 Dq, tetragonal field, rhombic field and the splitting of the E_g level, respectively. The quadrupole splitting data indicate that distortion from cubic symmetry increases in the order oxalate < malonate < maleate. DTA, TGA and Mössbauer studies indicate elimination of one molecule of maleic acid at 235 °C. The resulting product shows a less distorted structure and this is attributed to the formation of maleato(2-)iron(II).     

Synthesis of a Lewis acid bearing cyclopentadienyl ligand and its tricarbonylmanganese(I) complex

The synthesis of a bimetallic compound comprising a Lewis acidic organochlorostannane and a transition metal carbonyl is reported. The target complex, [(CO)₃Mn(η⁵-C₅H₄(CH₂)₃SnMe₂Cl)], 2, is prepared in four steps. The final step involves an exchange reaction between [(CO)₃Mn(η⁵-C₅H₄(CH₂)₃SnMe₃)], 1, and SnMe₂Cl₂. Infrared spectroscopy demonstrates no interaction between the Lewis acid and lone pair on the carbonyl oxygen.     

Substituent and solvent effects on tautomeric equilibria of barbituric acid derivatives and isoterically related compounds

N-Mono and N,N-dialkyl/diarylbarbituric acids exist in solution as a single tautomer. The ¹³C nmr spectroscopy shows that they are present in the triketo form in a number of polar and non-polar solvents. 2-Thiobarbituric acid derivatives, however, show extensive tautomerization. Their ¹³C chemical shift assignments were achieved by utilizing models 11a , 11c , 12b and 12d and from which relative tautomer distribution ratios were determined. These ratios were correlated with the dielectric constant of the various solvents (?). Thio-barbituric acids also formed adducts with solvents having carbonyl groups, characteristic observed only with barbiturates possessing the thione or thiophenolic group. 6-Amino and 6-methyluracils and thiouracils exist in DMSO solution as stable “ene” forms as do orotic acid, 24 , and its thio analogue 25. Compound 25 undergoes disproportionantion and tautomerization when heated or on prolonged standing in solution. Literature contradictions regarding the structure of “4,6-dihydroxypyrimidine,” 26 , were resolved and its tautomers in solution correctly assigned by ¹³C nmr. Anions of barbiturics and related systems exist in one of the two possible types A and B, depending on whether ring nitrogens are substituted (type A), or not (type B). Rapid H/D exchange at C₅ was evident from C-deuterium coupling. The redistribution of charge through C₄(C₆) carbonyl groups shown by ¹³C shifts of carbonyl carbon atoms of up to 10 ppm as compared to the CO carbons of the neutral species was evident.