Tandem GC/MS: A useful tool for studying end-capping reactions of oligo(styryl)lithium anions

Anionic living polymerization methods, using organometallic initiators such as butyllithium reagents, have proven useful for, inter alia, styrene polymerization and are amenable to subsequent functionalization of poly(styryl)lithium in the termination step. In this study, general methods for the selective preparation of small styrene oligomers and termination of the intermediate oligo(styryl)lithium anions were investigated. The crude reaction mixtures were analyzed directly by tandem gas chromatography/mass spectrometry (GC/MS). Of the carbon- and silicon-based electrophiles tested, chloro(chloroalkyl)silanes, Cl-SiR₂(CH₂)_nCl in particular, were shown by GC/MS to be regioselective end-capping reagents, thus allowing subsequent transformation to the primary amine. The combined GC/MS data allow not only an estimate of the degree of functionalization, but also the identification of by-products, thus providing insight into the end-capping process that otherwise might be difficult to access. © 1995 John Wiley & Sons, Inc.     

Convenient and High-Yielding Preparations of Mono(5-carboxy-2-ethylpentyl) Phthalate and its Ring-Deuterated Isomer – The “Third” Major Metabolite of Bis(2-ethylhexyl) Phthalate

Summary. The synthesis of an oxidative major metabolite of bis(2-ethylhexyl) phthalate is described. The target molecule and its ring-deuterated isomer were obtained via acylation of the appropriate -hydroxy benzyl ester or the corresponding carboxylate with phthalic anhydride or phthalic anhydride-d₄. All transformation steps proceed with high yields.     

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.     

High performance liquid chromatographic separation of dipeptide and tripeptide enantiomers using a chiral crown ether stationary phase

A chiral stationary phase (CSP) based on (-)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was evaluated for the direct resolution of the enantiomers of dipeptides and tripeptides. The type and concentration of the acid and the methanol content were optimized with regard to retention time and resolution using Ala-Phe as model peptide. A mobile phase consisting of 10 mM sulfuric acid in 70% aqueous methanol was applied to the separation of a set of 16 structurally diverse dipeptides and tripeptides. Generally, the configuration of the amino acid at the N-terminus determined the enantiomer elution order. With a few exceptions the LL- and LD-enantiomers interacted stronger with the CSP compared to the corresponding DD- or DL-enantiomers. The experimental conditions also allowed the simultaneous separation of all four stereoisomers of Ala-Phe. Addition of ammonium sulfate generally reduced retention times and enantiomer resolution. Addition of triethylamine as modifier led to an overall increase of the retention times while the resolution did not show a general trend, increasing in the case of Ala-Ala but decreasing in the case of Ala-Phe.     

双2-乙酰基二茂铁合汞的合成及其晶体结构

标题化合物(C24H22Fe2HgO2)3是由2 氯汞基 1 乙酰基二茂铁与乙二胺反应得到的,其结构通过单晶X 射线衍射法确定。其晶体属三斜晶系,P 1空间群,Mr=1964 12,a=10 193(2),b=11 504(2),c=14 413(3) ,α=92 21(3),β=104 12(3),γ=102 67(3)°,V=1591 55(5) 3,Z=1,Dc=2 049mg/cm3,μ=8 583mm-1,F(000)=942,最终偏离因子为R=0 0859,wR=0 2617。该晶体中同时含有meso型及dl型分子,各分子中Hg原子的配位情况不一样。meso分子中的两个二茂铁是相互平行的,而另两分子dl型的二茂铁是相互垂直的。Hg原子以桥联形式连接两个二茂铁部分。meso型与dl型分子通过Hg O弱配位作用相连。     

Synthesis of 6（E）—Geranylgeraniol—19—oic Acid

Facile synthesis of 6(E)-geranylgeraniol-19-oic acid 1,a naturally occurring alicyclic diterpene acid, by a Horner-Wadsworth-Emmons olefination of two readily available fragments 2 and 3,is described.     

Studies on Interactions of Antibiotics with Serum Albumin by Surface Plasmon Resonance Biosensor

Introduction Humanserumalbumin(HSA)isawell known transportproteinforavarietyofmoleculesandions[1].Thebindingofadrugtoserumalbuminhasimportant pharmacokineticconsequencesbecauseitinfluences distribution,excretionandpharmacologicaleffectsof thedruginthebody…     

2,5-二甲基-4-羟基-3(2H)呋喃酮的合成

以乙酰丙酮(1)为原料，经电解氧化偶联，Paal-Knorr闭环，Baeyer-Villiger氧化，水解等步骤，合成了一种重要的杂环香料，2,5-二甲基-4-羟基-3(2H)呋喃酮(6)。     

[Cu(H2O)(phen)2](CIO4)2的晶体结构

标题化合物晶体属三斜晶系;空间群为P₁;晶胞参数:a=8.182(2)Å,b=10.389(2)Å,c=16.261(5)Å,α=99.38(2)°,β=89.97(2)°,γ=113.18(2)°;Z=2,两个phen上的四个N原子和一个配位水中的O原子围绕中心体Cu原子形成一个畸变的三角双锥构型,配位水与阴离子ClO₄^-中的O原子形成氢键。