γ- And δ-lycorane

Hydrogenation of -anhydrodihydrocaranine (V) or anhydrocaranine (VII) with Adams catalyst in acetic acid or the Hauptmann reduction of -dihydrocaranone (XX) yielded (—)γ-lycorane (XVII). Catalytic reduction of β-anhydrodihydrocaranine (IX) with palladium-carbon in ethanol gave (+)γ-lycorane (XVIII), while with Adams catalyst in acetic acid it afforded (+)δ-lycorane (XIX) along with (—)β-lycorane (III). Reduction of anhydrocaranine in ethanol gave (±)γ-lycorane which was also obtained by hydrogenation of anhydrolycorine (X). Based on these findings, the configurational structures of -, β-, γ- and δ-lycorane were established and the configuration of dihydrolycorine was confirmed.     

(—)β-Lycorane

Hydrogenation of diacetyllycorine (Ib) was found to be the most effective route for conversion of lycorine (Ia) into β-dihydrocaranine (II). The Hauptmann reduction of 1-deoxy-β-dihydrolycorin-2-one (XII) or the Clemmensen reduction of 1-0-acetyl-β-dihydrolycorinone (XI) followed by hydrogenation afforded (—)β-lycorane (X), which, in view of the sequence of reactions used in these transformations, is considered to have the same configurational structure as the skeleton of β-dihydrocaranine. This lycorane was also obtained by the Hauptmann reduction of β-dihydrocaranone (VIII). A procedure for preparing (—)-lycorane (V) from 1-0-acetyllycorin-2-one (XIV) was also worked up.     

Synthesis of γγγ-trifluorocarbonyl compounds

γγγ-Trifluorocarbonyl compounds are easily obtained in a good yield by introduction of the 1,1,1-trifluoroethyl moiety (CF₃-CH₂-) on the -methylene group of a ketone.     

Zur struktur des dimeren β-mercaptozimtaldehyds

Attempts to prepare β-thioketoaldehydes from β-chlorovinylaldehydes and sodium sulphide lead in the case of β-chlorocinnamic aldehyde and sodium sulphide to a dimer of β-mercaptocinnamic aldehyde. ¹ The structure of the dimer was proved by means of IR-, ¹H-NMR- and ¹³C-NMR-spectroscopy and established as bicyclo-[3.3.1]-5,7-diphenyl-3-hydroxy-2-oxa-6, 9-dithia-nonene-(7).     

A new approach to the synthesis of 2β- and 3β-hydroxygibberellins

The first examples of the use of hydroxyl inversion reactions to prepare the gibberellin plant hormones are described. Treatment of 2- and 3-mesylates with caesium acetate gave, after hydrolysis, good yields of the required 2β- and 3β-hydroxygibberellins. Alternatively inversion of the 2-mesylate and hydrolysis of the 7-methyl ester may be achieved in one-pot by treatment of (2) with potassium superoxide.     

Controversy about β-tricalcium phosphate

The calcium phosphate which corresponds to the formula Ca₃(PO)₄ · nH₂O (2<n<3) was isolated from solutions with Ca/P molar ratio 0.2 and pH 7. The compound was characterised by chemical and thermogravimetric analyses, Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction. The FTIR spectra were compared with spectra of β-tricalcium phosphate (β-TCP) in the atlases for analysis of urinary calculi and other literature data.     

Vibrational spectroscopic detection of H-bonded β- and γ-turns in cyclic peptides and glycopeptides

The conformation of N-glycoproteins and N-glycopeptides has been the subject of many spectroscopic studies over the past decades. However, except for some preliminary data, no detailed study on the vibrational spectroscopy of glycosylated peptides has been published until recently.

This paper reports FTIR spectroscopic properties in DMSO and TFE of the N-glycosylated cyclic peptides cyclo[Gly-Pro-Xxx(GlcNAc)-Gly-δ-Ava] 3a and 3b in comparison with data on the non-glycosylated parent peptides cyclo(Gly-Pro-Xxx-Gly-δ-Ava) 2a and 2b [a, Xxx = Asn; b, Xxx = Gln; δ-Ava = NH-(CH₂)₄-CO] and N-acetyl 2-acetamido-2-deoxy-β- -gluco pyranosylamine (GlcNAc-NHAc, 4). The assignment of amide I band frequencies to conformation is based on ROESY experiments and determination of the temperature coefficients in DMSO-d₆ solution. (For the synthesis and NMR characterization of 2a and 3a see Ref. [19].)

Cyclic peptides are expected to adopt folded (β- and/or γ-turn) conformations which may be fixed by intramolecular H-bonding(s). A comparison of the temperature coefficients of the NH protons and amide I band frequencies and intensities suggests that in DMSO there is no significant difference in the backbone conformation and H-bond system of the N-glycosylated models and their parent cyclic peptides. The common feature of the backbone conformation of models 2 and 3 is the predominance of a 1 ← 4 (C₁₀) H-bonded type II β-turn encompassing Pro-Xxx or Pro-Xxx(GlcNAc), respectively. The ROESY connectivities in the Asn(GlcNAc) model (3a) have not been found to reflect intramolecular H-bondings between the peptide and the sugar.

The unique feature of the FTIR spectra in DMSO of the cyclic models is the lack or weakness of low-frequency (< 1640 cm⁻¹) amide I component bands. In TFE the amide I region of the FTIR spectra shows an increased number of components below 1650 cm⁻¹ reflecting a mixture of open and H-bonded β- and γ-turn conformers.

Because of its destabilizing effect upon γ-turns and other weakly H-bonded structures, DMSO decreases the number of backbone conformers. DMSO also destroys side-chain-backbone H-bondings of type C₇, C₆ or C₈. Possible ‘glyco’ C₇ H-bondings in GlcNAc-NHAc (4) or in glycopeptides 3a and 3b cannot resist the effect of DMSO either.

The FTIR data in TFE of models 2–4 suggest that the acceptor amide group of strong C₇ H-bondings in peptides and glycopeptides absorbs at 1630 ± 5 cm⁻¹ and that of bifurcated H-bondings between 1600–1620 cm⁻¹.     

Synthesis of aryl β-D-glucopyranosides and aryl β-D-glucopyranosiduronic acids

Tetra-O-benzyl--D-glucopyranosyl bromide in dichloromethane reacts stereospecifically with solutions of phenols in aqueous sodium or potassium hydroxide, in the presence of phase transfer catalysts, to give good yields of tetra-O-benzyl aryl-β-D-glucopyranosides which are converted into the corresponding aryl β-D-glucopyranosiduronic acids by sequential catalytic debenzylation and catalytic oxidation.     

Solution-phase synthesis of ICG-001, a β-turn peptidomimetic molecule inhibitor of β-catenin–Tcf-mediated transcription

The solution-phase synthesis of the β-turn peptidomimetic ICG-001, a selective inhibitor of Wnt/β-catenin signalling, which has been found to be important for both initiation and progression of cancers of different tissues and has been exploited as an extremely useful chemogenomic tool, was developed. This route is particularly suitable for the multigram scale preparation of ICG-001.     

Direct conversion of β,γ-unsaturated esters into lactones induced by TMS-I

β,γ-unsaturated esters readily prepared by photodeconjugation are converted in one step into butanolides by treatment with TMS-I. The reaction has been extended to the access to -alkylidene lactones.     

C---H bond activation by rhodium(I) and the mechanism of the olefin isomerization: new synthesis of β,γ-unsaturated ketones via η- or η-alkylallylrhodium(III) complexes by reductive elimination

Acylrhodium(III)-η³-1-ethylallyl complex (7) was prepared by the reaction of 8-quinolinecarboxaldehyde (3) and 1,4-pentadienerhodium(I) chloride (2) by C---H bond activation, followed by hydrometallation, and double bond migration. Higher concentrations of pyridine as coordinating ligand transforms η³-1-ethylallylrhodium(III) complexes (8a,8b) into η¹-pent-2-enylrhodium(III) complex (11a). Acylrhodium(III)-η³-syn,anti-1,3-dimethylallyl complex (14) was also prepared from 1,3-pentadienerhodium(I) chloride (16) and 3. The reductive elimination of acylrhodium(III)-η¹- and -η³-1-alkylallyl complexes by trimethylphosphite gives various β,γ-unsaturated ketones.     

Small angle X-ray scattering from lamellar phase for β-3,7-dimethyloctylglucoside/water system: comparison with β-n-alkylglucosides

Small angle X-ray scattering (SAXS) is measured for the lamellar phase in aqueous systems of 1-o-β-3,7-dimethyoctyl-D-glucopyranoside (β-Glc(Ger)), which has recently been prepared by us, 1-o-β-decyl-D-glucopyranoside (β-GlcC₁₀), and 1-o-β-octyl-D-glucopyranoside (β-GlcC₈). The repeat distance d obtained from the position of the diffraction peak does not follow the swelling law d = 2δ_hc/_hc, where δ_hc and _hc are the thickness and the volume fraction of the hydrophobic layer, respectively. This may result from the fact that δ_hc increases and, equivalently, the surface area per surfactant molecule (a_s) decreases with increasing concentration. So we calculate δ_hc and a_s from the observed d value at each concentration using the above swelling law. The half-thickness δ_hc increases in the order β-GlcC₈ < β-Glc(Ger) < β-GlcC₁₀ at a fixed concentration. On the other hand, the data on a_s for β-GlcC₁₀ and β-GlcC₈ lie on the same line and the data for β-Glc(Ger) lies above this line. These results suggest that the cross-sectional area of the geranyl chain is larger than that of the glucose headgroup. Existence of water filled defects in bilayer sheets is also discussed based on the SAXS pattern and the concentration dependence of d.     

Studies of an inclusion complex of a redox-active barbiturate with β-cyclodextrin

The effects of β-cyclodextrin (β-CD) on the spectral properties and electrochemical behaviour of barbitone sodium were studied using electrochemical and optical techniques. The apparent changes in the UV-visible absorption spectrum and fluorescence quenching of the barbiturate upon addition of β-CD afford clear evidence of the inclusion complex formation of β-CD in aqueous solutions. The redox acitivity of barbitone sodium in both the absence and presence of β-CD was assessed by an electrochemical method in 0.05 M potassium nitrate-nitric acid (pH 1.8) solution. While the complexation reaction remains is equilibrium, the apparent formation constant of the inclusion complex could be obtained by either spectral or electrochemical methods. Quantitative evaluation of the data gave 326 l mol⁻¹ under equilibrium conditions at 20°C. Possible conclusions are discussed on the basis of environmental changes around the barbiturate molecules on inclusion.     

π-Olefin-Iridium-Komplexe : XXI. Synthese und Kristallstrukturen heterobinuclearer Komplexe mit wannenförmiger, synfacial gebundener η: η-Benzolbrücke

CpIr(η⁴-C₆H₆) (2) has been obtained in high yield by a four-step synthesis. Thermal reaction of 2 with CpCO(C₂H₄)₂ and photochemical reaction of 2 with CpRh(C₂H₄)₂ or CpRh(C₂H₄)₂ give the compounds μ-(η³: η³-C₆H₆)CoIrCp₂ (3), μ-(η³: η³-C₆H₆)RhIrCp₂ (4), and μ-(η³: η³-C₆H₆)(RhCp)(IrCp) (5), respectively. The X-ray crystallography data of 3 and 4 reveal a boat-shaped conformation of the synfacially bridging benzene ligand with a rather long Co---Ir bond distance in 3 and a relatively short Rh---Ir bond length in 4 which are caused by almost constant folding angles of the benzene unit. The dynamic behaviour of the benzene bridge was investigated by NMR spectrometry.     

γ-Fe2O3纳米纤维的丙酮敏感特性

采用静电纺丝法制备了PVP/FeC₆H₅O₇复合纳米纤维, 并将复合纤维在500 ℃高温烧结3 h, X射线衍射分析(XRD)表明, 烧结后的产物为正尖晶石结构的γ-Fe₂O₃晶体. 扫描电子显微镜(SEM)观测结果表明, 制得了直径均匀、 连续的复合纳米纤维, 其平均直径约为1000 nm; 烧结后的γ-Fe₂O₃纳米纤维保持了其连续性, 但纤维发生了收缩, 直径较烧结前小, 平均约为600 nm. 比表面积分析表明, γ-Fe₂O₃纳米纤维比表面积为57.18 m²/g. 气敏性能测试结果表明, 230 ℃为γ-Fe₂O₃纳米纤维检测丙酮气体的最佳工作温度. 在此温度下, γ-Fe₂O₃纳米纤维对丙酮气体表现出高响应度[S=6.9, c(Acetone)=7.88×10⁴ mg/m³]和线性度(7.88×10²~1.58×10⁵ mg/m³浓度范围内). 同时, γ-Fe₂O₃纳米纤维气体传感器件还表现出良好的长期稳定性.     

Synthesis, structure and hydrogenation catalytic activity of [Ru3(μ3,η-ampy)(μ,η:η-PhC=CHPh)(CO)6(PPh3) (Hampy = 2-amino-6-methylpyridine)

The compound [RU₃(μ₃,η²- -ampy)(μ₃η¹:η²-PhC=CHPh)(CO)₆(PPh₃)₂] (1) (ampy = 2-amino-6-methylpyridinate) has been prepared by reaction of [RU₃(η-H)(μ₃,η²- ampy) (μ,η¹:η²-PhC=CHPh)(CO)₇(PPh₃)] with triphenylphosphine at room temperature. However, the reaction of [RU₃(μ-H)(μ₃, η² -ampy)(CO)₇(PPh₃)₂] with diphenylacetylene requires a higher temperature (110°C) and does not give complex 1 but the phenyl derivative [RU₃(μ₃,η²-ampy)(μ,η ¹:η² -PhC=CHPh)(μ,-PPh₂)(Ph)(CO)₅(PPh₃)] (2). The thermolysis of complex 1 (110°C) also gives complex 2 quantitatively. Both 1 and 2 have been characterized by0 X-ray diffraction methods. Complex 1 is a catalyst precursor for the homogeneous hydrogenation of diphenylacetylene to a mixture of cis- and trans -stilbene under mild conditions (80°C, 1 atm. of H₂), although progressive deactivation of the catalytic species is observed. The dihydride [RU₃(μ-H)₂(μ ₃,η²-ampy)(μ,η¹:η²- PhC=CHPh)(CO)₅(PPh₃)₂] (3), which has been characterized spectroscopically, is an intermediate in the catalytic hydrogenation reaction.     

Effets des substituants sur la conformation du cycle γ-lactonique : I. Dérivés de la γ-butyrolactone

The structural study of some γ-butyrolactones substituted (i) in position 2 (position ): C₄H₄O₂Br₂ (II) and C₄H₅O₂R [R = Oφ (III); R = OCOφ (IV); R = OH (V); R = Br (VI); R = Cl (VII)] or (ii) in position 3 or 4 (β or β′): C₄H₅O₂Cl (VIII and IX) has been carried out by using different techniques of physical chemistry. Crystallographic data analysis demonstrates that in the solid state, 2,2-dibromo-γ-butyrolactone, unlike the 2,2-diphenyl-γ-butyrolactone, adopts an “envelope” structure which is comparable to those of compounds (III) and (IV). Spectroscopic data relative to the methylene bending mode δ(CH₂) are interpreted for the dissolved state in terms of rigid (III, IV, V, IX) or exchanging (VI, VII, VIII) “envelope” forms. For and β halogenated derivatives (VI, VII, VIII), quantitative analysis of infrared spectra shows a pseudo-axial predominance in apolar solvents, as found by application of the PCILO method. Interpretation of NMR spectra recorded at 250 MHz (III, IV, V, VI) confirms the data obtained by vibrational spectroscopy.     

Übergangsmetallketen-verbindungen : XXIX. Cyclopropylsubstituierte η- und η-Ketenylverbindungen des Wolframs; Elektronenstruktur und Bindungsverhältnisse in Carbonyl(η-cyclopentadienyl)(η-cyclopropylketenyl) (trimethylphosphin)wolfram

Synthesis and spectroscopic data of carbonyl(η⁵-cyclopentadienyl)(η²-cyclopropylketenyl) (trimethylphosphine)tungsten and dicarbonyl(η⁵-cyclopentadienyl)(η¹-cyclopropylketenyl) (trimethylphosphine)tungsten are reported. The electronic structure of, and types of bonding in carbonyl(η⁵-cyclopentadienyl)(η²-cyclopropylketenyl) (trimethylphosphine)tungsten are described.     

The octant rule: XXIII. antioctant effects in γ,δ -unsaturated ketones.

The and -benzyl derivatives (1 and 2, respectively) of (+)-camphor have been synthesized and are found to exert a strong influence on the circular dichroism n→π^* Cotton effects: 1: Δε³⁰¹_max -0.36 (n- heptane) and 2: Δε³⁰²_max +3.22, relative to camphor: Δε³⁰⁴_max +1.8 (n-heptane). Evidence for electric dipole transition moment coupling in these γ, δ -unsaturated systems is found in the n→π^* UV: 1: ε²⁹¹_max 84 (n-heptane) and 2: ε²⁸⁵_max 303, relative to camphor: ε²⁹⁰_max 25.     

Excimer fluorescence in β-9,10-dichloroanthracene crystals

The fluorescence of single crystals of β-9,10-dichloroanthracene at 4.2 K consists solely of excimer emission (τ = 95 ± 5 ns). The absence of monomenc emission shows that excimer formation in this crystal is not a thermally activated process. This result is confirmed by excimer-excimer annihilation studies (γ(4.2 K) = 6 × 10⁻¹³, γ(298K) = 3 × 10⁻¹² cm³ s⁻¹).