Enzymatic resolution of (RS)-1-phenylalkyl β-d-glucosides to (R)-1-phenylalkyl β-primeverosides and (S)-1-phenylalkyl β-d-glucosides via plant xylosyltransferase

The stereoselective xylosylation of (RS)-1-phenylalkyl β-d-glucosides was investigated using plant xylosyltransferase isolated from cultured Catharanthus roseus cells. Enzymatic xylosylation of (RS)-1-phenylethyl β-d-glucoside afforded (R)-1-phenylethyl β-primeveroside and (S)-1-phenylethyl β-d-glucoside. The (R)-selective xylosylation of (RS)-1-phenylbutyl β-d-glucoside also occurred to give (R)-1-phenylbutyl β-primeveroside and recovered (S)-1-phenylbutyl β-d-glucoside.     

Photochemical reactivity of α,β-unsaturated δ-lactams: Synthesis of seco-steroids. Photochemical reactions. XIII [1]

The UV. irradiation of 17 β-hydroxy-2-aza-4-androsten-3-one (1) , N-methyl-17 β-hydroxy-2-aza-4-androsten-3-one (3) , 17 β-hydroxy-4-aza-5 β-androst-1-en-3-one (2) and N-methyl-17 β-hydroxy-4-aza-5 β-androst-1-en-3-one (4) , gives rise to 1,10-seco (from 1 and 3 ) and 5, 10-seco (from 2 and 4 ) steroids.     

β-Cyclodextrin Inclusion Complexes of 2-Hydroxyfluorene and 2-Hydroxy-9-fluorenone: Differences in Stoichiometry and Excited State Prototropic Equilibrium

We report that 1:1 and 1:2 complexes are formed for 2-hydroxy-9-fluorenone with β-cyclodextrin (β-CD) and that there is an unusual red shift in emission at higher concentrations of β-CD. Between different stoichiometries of the complexes the titrimetric curves for the neutral–anionic equilibria for the guests differ drastically and so do the excited state pK values. The formation of an 1:1 inclusion complex with 2-hydroxy-9-fluorenone (2HFN) as the guest in β-CD with the binding constant (K) of 606.65 L·mol^?1 was determined. The ground and excited state pK _a values for the neutral–mono-anion equilibrium are not affected by β-CD. Hence the hydroxyl group is considered exposed in the aqueous environment. Two different types of inclusion complexes of 2HFN were observed in β-CD. The 1:2 complex of 2HFN shows a red shift from the 1:1 complex and is less fluorescent that the 1:1 complex. The red shift reveals that the 1:2 complex is more stabilized than the 1:1 complex. The excited state pK _a values in both complexes with β-CD are higher that those in aqueous solution. This shows that the complexation makes the molecule less acidic in the S1 state. The β-CD molecule is perceived as not able to encapsulate the 2HFN molecule fully, but the larger rim of the β-CD comes closer to the C=O group. The other half of the 2HFN molecule is encapsulated by the second β-CD molecule and thus there is formation of the 1:2 inclusion complex at higher concentrations of β-CD.     

Friedel-crafts cyclisation—IV: Intramolecular vs intermolecular acylation with β-aryl derivatives of propionyl chloride in aromatic substrates

Studies on the aluminium chloride-catalysed behaviour of β-phenylpropionyl, β,β-diphenylpropionyl, and β,β,β-triphenylpropionyl chlorides in anisole and some other aromatic stubstrates under standardised conditions are discussed. β,β-Diphenylpropionyl chloride gave yields of up to 27% 3-phenylindan-1-one in anisole and is one of the most easily cyclised acid chlorides so far reported. β,β,β-Triphenylpropionyl is less easily cyclised in anisole to 3,3-diphenylindan-1-one and its transformation product 2,3-diphenylind-1-one. The expected open-chain ketone is completely decomposed into products of αβ-ketonic cleavage and a subsequent redox reaction. Differences in ratios of intermolecular to intramolecular acylation (now called o/c ratios) are discussed.In benzene, β-bis-(p-chlorophenyl)propionyl chloride gave, in addition to the previously noted β-bis-(p-chlorophenyl)propiophenone (48%), the folloowing compounds: 6-chloro-3-(p-chlorophenyl)indan-1-one (4%) (the intramolecular acylation product), β-(p-chlorophenyl)-β-phenylpropiophenone (2·3%), ββ-diphenylpropiophenone (0·5%), 3-(p-chlorophenyl)-indan-1-one (5·2%). The transformation processes are discussed. Aluminium chloride-catalysed β-aryl exchange in acid chlorides is reported for the first time, but β-aryl exchange does not occur in ββ-(or 3,3-)di-aryl derivatives of indan-1-one.     

The predicted unfolding order of the β-strands in the starch binding domain from Aspergillus niger glucoamylase

The unfolding of the β-strands in the starch binding domain from Aspergillus niger glucoamylase was predicted to follow the order of β3→β2→β6→β5→β4→β1→β7 by 600 ps molecular dynamics simulations at 300, 400, and 600 K. The interior region around β-strands 2 and 3 acts as the initiation site for unfolding. β-Strands 1 and 7 are probably stabilized by the disulfide bond formed between Cys509 and Cys604. β-Strand 4 is stabilized by forming an antiparallel β-sheet with β-strand 1. Hydrophobic and electrostatic interactions between side chains instead of the hydrogen bonds are important in stabilizing these β-strands, thus the entire starch binding domain.     

Photochemical reactions of β-aminovinyl aryl thioketones

Irradiation of β-aminovinyl aryl thioketones ( 1a-b ) afforded β-aminovinyl aryl ketones ( 2a-b ). 2H-Thiopyran derivatives ( 4a-b ) were obtained when β-aminovinyl phenyl thioketone ( 1a ) was irradiated with methyl acrylate and acrylonitrile. 4H-Thiopyran derivatives ( 6,8 ) were also obtained thermally in the reaction of β-aminovinyl phenyl thioketone ( 1a ) and methyl propiolate and maleic anhydride.     

Immunological comparison of constitutive β-lactamases of gram-negative bacteria by neutralization in zymogram gels: Properties of anti-TEM-1 and anti-TEM-2 sera

The zymogram technique was applied to a β-lactamase neutralization assay with anti-TEM-1 and anti-TEM-2 sera. Both were shown to contain neutralizing antibodies directed towards various β-lactamases of Gram-negative bacteria. The quantitative neutralization allowed classification into five groups of the 28 β-lactamases used as standards and 61 from clinical isolates. In the first were enzymes such as TEM-1 and TEM-2 including TLE-1, SHV-1, SHV-2, penicillinases of Klebsiella pneumoniae and CTX-1. Partial neutralization distinguished two groups containing the CARB group of enzymes, which are different from PSE-2 and PSE-3, and the MAL penicillinases of Levinea malonatica, which are different from L. amalonatica enzymes. Broad spectrum β-lactamases of K. oxytoca constituted a unique group of partially neutralized enzymes. Among the β-lactamases not neutralized by either serum were the plasmid-mediated OXA-enzymes, various species-specific β-lactamases and cephalosporinases.The antigenic similarities of the enzymes appeared to correlate with the extent of similarities of their catalytic properties, namely those of penicillinases. Such comparisons between the β-lactamase groups provide an indirect approach to the physiological and structural analysis of established and recently evolved β-lactamases.     

Water-insoluble β-cyclodextrin polymer crosslinked by citric acid: synthesis and adsorption properties toward phenol and methylene blue

Water-insoluble β-cyclodextrin polymer (β-CDP) crosslinked by citric acid was obtained with a yield of 65% through an environment friendly synthesis procedure. FT-IR spectra disclosed that the hydroxyl groups of β-CD had reacted and condensated with the carboxyl groups of citric acid, and at the same time the structural characteristics of β-CD were essentially maintained in β-CDP. The β-CDP exhibited notable adsorption capability toward phenol (q _max = 13.8 mg g^?1) and especially large adsorption capability toward methylene blue (q _max = 105 mg g^?1). The concentration of methylene blue in water could be reduced to 0.11 mg L^?1 by the β-CDP, indicating the excellent adsorption sensitivity of β-CDP toward methylene blue. The adsorption results disclosed that the interior cavity and inclusion property of β-CD were maintained in the synthesized β-CDP.     

Complexation studies of pioglitazone hydrochloride and β-cyclodextrin: NMR (1H, ROESY) spectroscopic study in solution

Pioglitazone hydrochloride (PIO) is an agonist of the peroxisome proliferator-activated receptor γ (PPARγ), used to treat diabetes. ¹H-NMR spectroscopic analysis of varying ratios of β-cyclodextrin (β-CyD) and PIO in D₂O confirmed the formation of β-CyD–PIO inclusion complex in aqueous solution. The 1:1 stoichiometry of β-CyD–PIO inclusion complex was determined by Scott’s plot method and binding constant (K _a ) was calculated to be 155 M^?1. 2D ROESY experiments confirmed that the phenyl ring of PIO act as a guest and deeply penetrate in β-CyD cavity from wider as well as narrower rim side and form two 1:1 stable inclusion complexes. Some of the PIO protons exhibited splitting, in the presence of β-CyD, indicating chiral differentiation of PIO by β-CyD.     

[M6Om(C25N4H18)n]2-(M=W, Mo; n=1, 2; m=17,18)的二阶非线性光学性质的理论研究

运用密度泛函理论(DFT)的BP86方法, 对[M6Om(C25N4H18)n]2-(M=W, Mo; n=1, 2; m=17,18)进行了几何结构优化, 其中Mo系列结构化合物优化的几何结构与实验值吻合较好. 在净电场为零的条件下, 运用DFT/LB94方法计算了体系的二阶非线性光学系数β值: 体系1和2的βvec值分别为154.4×10-30和124.8×10-30 esu. 表明它们具有较大的二阶非线性光学系数, 且Mo系列比W系列的β值大. 而体系3和4的βvec值分别为218.0×10-30和191.8×10-30 esu. 体系3和4的βvec值分别比体系1和2的大, 表明增加给体的数目有利于提高NLO响应, 但都小于它们的2倍.     

Global and distribution analysis of fluorescence decays and spectrofluorimetric determination of stoichiometry and association constant of the inclusion complex of 2-amino-5,6-dimethyl-benzimidazole with beta-cyclodextrin

The steady state and time-resolved fluorescence study of 2-amino-5,6-dimethyl-benzimidazole (ADBI) have been studied in aqueous solution of β-cyclodextrin (β-CD). The fluorescence decays were analyzed by global analysis and distribution analysis in order to get insight about the inclusion process. The fluorescence lifetime of ADBI is increased in β-CD and an enhancement of the emission, is observed, together with negligible changes in the energy of ADBI in β-CD. The experimental data show that β-CD reacts with ADBI to form a 1:1 host-guest complex with association constant was determined to be 2074±77 M⁻¹. Both global analysis and distribution analysis of the fluorescence decays support the formation of only 1:1 inclusion complex. AM1 calculation shows that the size of ADBI was appropriate for good insertion within the β-CD cavity and the inclusion of ADBI inside the β-CD cavity should takes place from the side of the amino group substituent.     

New approach to exclusive formation of both enantiomers of β-amino acid derivatives

A highly selective two-step approach to chiral β-amino esters via the hydride reductive amination of chiral allenes is reported. β-Enamino esters were obtained from the nucleophilic addition of amines to 2,3-allenoates bearing a chiral auxiliary. The reduction of the (1R)-(−)-10-phenylsulfonylisobornyl β-enamino esters gave the corresponding β-amino esters with S configuration whereas the reduction of the (1S)-(+)-10-phenylsulfonylisobornyl β-enamino esters led to β-amino esters with R configuration. The rationalization of the observed selectivity was supported by semi-empirical molecular orbital calculations (PM3).     

Spektrophotometrische Untersuchung der Eisen(III)-Komplexe mit o-Methylbenzamidoxim

The complex formation of Fe³⁺ with o-methyl benzamide oxime was studied spectrophotometrically in methanol solution. The stepwise process gives complexes 1∶1, 1∶2 and 1∶3. The formation constants are lgK ₁ = lg β₁ = 1,88 ± 0,12, lgK ₂ = 3,53 ± 0,2, lgK ₃ = 4,96 ± 0,2, lg β₂ = 1,65 ± 0,32 and lg β₃ = 1,43 ± 0,4, whereK ₃ = β₁ · β₂ · β₃. All measurements were carried out at 25°C and an ionic strength μ=1.     

Adamantoid Scaffolds for Multiple Cargo Loading and Cellular Delivery as β-Cyclodextrin Inclusion Complexes

There is huge demand for developing guests that bind β-CD and can conjugate multiple cargos for cellular delivery. We synthesized trioxaadamantane derivatives, which can conjugate up to three cargos per guest. ¹H NMR titration and isothermal titration calorimetry revealed these guests form 1 : 1 inclusion complexes with β-CD with association constants in the order of 10³ M⁻¹. Co-crystallization of β-CD with guests yielded crystals of their 1 : 1 inclusion complexes as determined by single-crystal X-ray diffraction. In all cases, trioxaadamantane core is buried within the hydrophobic cavity of β-CD and three hydroxyl groups are exposed outside. We established biocompatibility using representative candidate G4 and its inclusion complex with β-CD (β-CD⊂ G4 ), by MTT assay using HeLa cells. We incubated HeLa cells with rhodamine-conjugated G4 and established cellular cargo delivery using confocal laser scanning microscopy (CLSM) and fluorescence-activated cell sorting (FACS) analysis. For functional assay, we incubated HeLa cells with β-CD-inclusion complexes of G4 -derived prodrugs G6 and G7 , containing one and three units of the antitumor drug (S)-(+)-camptothecin, respectively. Cells incubated with β-CD⊂ G7 displayed the highest internalization and uniform distribution of camptothecin. β-CD⊂ G7 showed higher cytotoxicity than G7 , camptothecin, G6 and β-CD⊂ G6 , affirming the efficiency of adamantoid derivatives in high-density loading and cargo delivery.     

Synthesis of racemic cis-1-alkyl- and 1-aryl-2-aminocyclopropanecarboxylic esters

The title cyclic β-amino esters were synthesized stereo- and regioselectively. Starting from the corresponding 1-aryl- and 1-alkylcyclopropane-1,2-dicarboxylates, selective monosaponification and subsequent Curtius reaction leads to certain cis-1-alkyl- and 1-aryl-2-aminocyclopropanecarboxylic esters. These β-aminocyclopropanecarboxylate derivatives (β-ACCs) can be seen as useful building blocks for β-peptides.     

Spectroscopic studies on the inclusion complex formation between 7-iodo-8-hyroxyquinoline-5-sulfonic acid and β-cyclodextrin

Formation of an inclusion complex between 7-iodo-8-hyroxyquinoline-5-sulfonic acid (IHQS) and β-cyclodextrin is studied by spectrophotometry and ¹H NMR techniques. Spectral changes in the emission spectra upon the addition of β-cyclodextrin to IHQS in aqueous media were too small to allow for the determination of the binding constant. On the other hand; absorption spectra show a pronounced changes upon the addition of β-cyclodextrin that allowed for the determination of the binding constant. Absorption measurements show 1:1 inclusion of IHQS in the β-cyclodextrin cavity with an association constant of 135 ± 25 M^?1. ¹H-NMR studies are used to confirm the inclusion and to provide information about the geometry of IHQS inclusion in the cavity of β-cyclodextrin.     

Ultrasound-assisted rapid synthesis of β-cyanoepoxides using hypervalent iodine reagents

An elegant approach for the rapid synthesis of β-cyanoepoxides 3 by the epoxidation of β-cyanostyrenes 1 with PIDA 2a is described. The epoxidation of β-cyanostyrenes 1 was performed with 1.2 equiv. of PIDA 2a in MeCN-H₂O (1:1) at room temperature in ultrasonic bath. The epoxidation reactions were completed in short reaction time and β-cyanoepoxides 3 were isolated in 69–94% yields.     

Synthesis of polyfunctional β-Ketosulfides and their reactions with m-chloroperbenzoic acid and chlorine dioxide

The reaction of bromoacetophenone with various thiols furnished β-ketosulfides: 2-(1-methyl-1H-imidazol-2-ylsulfanyl)-1-phenylethanone, 2-(1H-imidazol-2-ylsulfanyl)-1-phenylethanone, 2-(2-hydroxyethylsulfanyl)-1-phenylethanone. β-Ketosulfoxides were obtained by the oxidation of β-ketosulfi des with m-chloroperbenzoic acid and chlorine dioxide.     

A study of the reaction of sulfur with organic compounds

The reaction of sulfur with isomeric exo-polychloro derivatives of iso- and n-propylbenzenes containing from 4 to 6 chlorine atoms in the side chain at 200°–300° C has been studied. The reaction of sulfur with α, β, β, β′-tetrachloro- and α, β, β, β′, β′-pentachlorocumenes leads to the formation of the previously unknown thianaphtheno-[2, 3-d]-1, 2-dithiole-3-thione (yield 48%) and thionaphtheno[2,3-d]-3-chloro-1, 2-dithiolium chloride (yield 65%), respectively. The sulfuration reaction of the isomeric exo-tetrachloro-and exo-pentachloro-n-propylbenzenes leads to the formation of 4-chloro-5-phenyl-1, 2-dithiole-3-thione (yield 5–35%). The exo-hexachloro derivatives of iso- and n-bromobenzenes, on being heated with sulfur, form only resinous sulfuration products.     

Synthèse de β-imidazolylcétones

The synthesis of β-imidazolylketones 1 and 2 is described. The compounds 1 are prepared by reaction of Mannich bases with the imidazole. Treatment of the imidazole with haloketones or α-ethylenic ketones or the reaction β-kétol with N,N'-thinoyldiimidazole lead to β-imidazolylketones 2 .