Derivatization of carboxylic acids with 9-bromomethylacridine using micellar phase-transfer catalysis

Summary Micellar phase-transfer catalysis (MPTC) offers the opportunity to derivatize carboxylic acids directly in an aqueous matrix without prior extraction of the acids into a suitable aprotic solvent. The currently developed MPTC system consists of a non-ionic surfactant, Arkopal N-130, an ion-pair agent, tetrakis-(decyl)-ammonium bromide, and a novel fluorescence reagent, 9-bromomethylacridine. The MPTC system can be applied to the derivatization of many types of carboxylic acids. The reaction rate is affected by the lipophilicity of the acid and by the presence of other functional groups. For lipophilic carboxylic acids the reaction is complete within 5 min at 60°C and pH 7.0.     

Stereochemistry of ketone olefination with methyl trimethylsilylacetate

High (Z)-stereoselectivity of olefination of methyl α-phenylthioalkyl and methyl α-phenylthioalkenyl ketones with methyl trimethylsilylacetate decreases in the case of ketones containing a higher alkyl-substituent in place of the methyl group. Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 1020–1021, April, 2005.     

利用差异衍生同步分析醛糖和酮糖

建立了一种可同时对醛、酮糖进行精确定性和定量分析的方法。以肌醇作为内标，用80％乙醇超声提取，利用醋酸酐和HMDS＋TMCS（1：3）进行差异衍生，在EI源下用SIM模式进行GC／MS分析。结果表明：11种标准单糖在1—4mg／L范围内线性良好；仪器检出限：醛糖在8．15—22．4μg／L之间；酮糖为2．32μg／L和3．47μg/L；高、中、低3个量的平均回收率在73．0％-95．7％，相对标准偏差在3．1％-10．0％。对枸杞游离单糖进行测定，各单糖含量分别在0．26—368．6mg／g。该方法弥补了以前单糖分析中的缺陷，对既含有醛糖又含有酮糖的样品可同时进行精确的定性定量分析。     

Migration behavior and enantioseparation of hydrobenzoin and structurally related compounds in capillary zone electrophoresis with a dual cyclodextrin system consisting of heptakis-(2,3-dihydroxy-6-O-sulfo)-beta-cyclodextrin and beta-cyclodextrin

Migration behavior and enantioseparation of racemic hydrobenzoin and structurally related compounds, including benzoin and benzoin methyl ether, in CZE with a dual CD system consisting of heptakis-(2,3-dihydroxy-6-O-sulfo)-beta-CD (SI-S-beta-CD) and beta-CD as chiral selectors in the presence and absence of borate complexation at pH 9.0 were investigated. The results indicate that enantioseparation of hydrobenzoin is mainly governed by CD complexation of hydrobenzoin-borate complexes with SI-S-beta-CD when SI-S-beta-CD concentration is relatively high. Whereas CD complexation of hydrobenzoin-borate complexes with beta-CD plays a significant role in enantioseparation when SI-S-beta-CD concentration is comparatively low. The (S,S)-enantiomer of the hydrobenzoin-borate complex was found to interact more strongly than the corresponding (R,R)-enantiomer with both SI-S-beta-CD and beta-CD. These two types of CD show the same chiral recognition pattern, but they exhibit opposite effects on the mobility of the enantiomers of hydrobenzoin-borate complexes. Enantiomer migration reversal of hydrobenzoin occurred in the presence of borate complexation when varying the concentration of beta-CD, while keeping SI-S-beta-CD at a relatively low concentration. Binding constants of the enantiomers of benzoin-related compounds to beta-CD and those of hydrobenzoin-borate complexes to SI-beta-CD were evaluated; the mobility contributions of all complex species to the effective mobility of the enantiomers of hydrobenzoin as a function of beta-CD concentration in a borate buffer were analyzed. In addition, comparative studies on the enantioseparation of benzoin-related compounds with SI-S-beta-CD and with randomly sulfate-substituted beta-CD were made.     

Reversed-phase liquid chromatographic method for the analysis of aminoglycoside antibiotics using pre-column derivatization with phenylisocyanate

A pre-column derivatization liquid chromatographic method has been developed for the analysis of aminoglycoside antibiotics using phenylisocyanate as a derivatization reagent. Derivatives including kanamycin, neomycin and gentamicin were formed by reaction of the analytes with phenylisocyanate in the presence of triethylamine. Phenylisocyanato groups were attached to corresponding amino groups of aminoglycoside and their molecular mass was confirmed by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). The experimental conditions for derivatization and separation of aminoglycoside derivatives were optimized and validated. A simple liquid chromatographic method for the determination of aminoglycoside antibiotics was demonstrated.     

Triterpenoids from plants of the genus Tamarix

The taraxeran-14-ene-type triterpenoids methyl 3-β-al-D-fridoolean-14-en-28-oate (1), 3-α-[3″,4′-dihydroxytrans-cinnamoyl]-oxy-D-fridoolean-14-en-28-oic acid (2), and β-sitosterol (3) were isolated from the aerial part of plants from the genus Tamarix (T. laxa, T. elongata) (Tamaricaceae). The structures of the triterpenoids were proved using spectral data (IR, UV, PMR, ¹³C NMR, 2D NMR ¹H-¹H COSY, HMQC, HMBC, mass). Compound 1 is new and not previously described in the literature. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 271–273, May–June, 2006.     

Redox Polymerization of Methyl Methacrylate in the Fluorous Triphasic System

Fluorous-phase chemistry is currently a topic of considerable interest1-6. Since fluoroustriphasic reactions were first described by the Curran and co-workers7, this triphasicsystem has been widely used for detagging7,8 and phase-vanishing reactions9-11. …     

Graft copolymerization of methyl acrylate onto potato starch initiated by ceric ammonium nitrate

A study was made of the ceric ammonium nitrate (CAN) initiated graft copolymerization of methyl acrylate (MA) onto potato starch. The variables affecting the graft were investigated. The optimums have been obtained; they are the concentrations of MA, CAN, and nitric acid (HNO₃) (1.08, 5.0 × 10^?3, and 0.081 mol/L, respectively). The reaction temperature is ca. 50°C and the reaction time is 2 h. The molecular weight of grafted poly(methylacrylate) has been determined. On the basis of experimental results, the mechanism of grafting has been explored, a new kinetic equation of the graft copolymerization is established: R_p = Kk_d [STOH] [Ce⁴⁺] + Kk_pk_d/k_t[STOH][M], where K, k_d, k_p, and k_t are constants. The equation fits the results of experiments. © 1993 John Wiley & Sons, Inc.     

Investigation of the detection limit for the determination,by pyrolysis-capillary GC,of the thickness of ultra thin PMMA layers coated on to PET film

The determination of nanometer thick layers of poly(methyl methacrylate) coated on to the surface of poly(ethylene terephthalate) film has been investigated by high resolution pyrolysis gas chromatography without sample pretreatment or modification of the instrumentation used. A good linear relationship was observed between the quantity of the characteristic pyrolysate and the thickness of the poly(methyl methacrylate) layer; the detection limit was sufficient to enable the quantitation of poly(methyl methacrylate)-to-poly(ethylene terephthalate) film thickness ratios of 1:20000 in composite materials.     

Synthesis and Adsorption Property of Two Polymeric Adsorbents with Pendent Ether Bonds

Two polymeric adsorbents, poly(methyl p-vinylbenzvl ether) and oolv(ohenvl p-vinylbenzyl ether), were synthesized from chloromethylated polystyrene, Their adsorptionproperty for phenol in hexane solution was investigated. The results showed that the twoadsorbents adsorb phenol from hexane solution through hydrogen-bonding and π-π stacking interaction.