Identification of bioactive compounds in Shaoyao‐Gancao decoction using β2‐adrenoceptor affinity chromatography

Shaoyao‐Gancao decoction, a Chinese herbal formula, is composed of Paeoniae Radix alba and Glycyrrhiza Radix et rhizoma . It has been widely used to treat muscle spasms and asthma. However, little is known about the bioactive components of Shaoyao‐Gancao decoction. In the present study, the bioactive compounds in water‐extract of Shaoyao‐Gancao decoction were separated by the immobilized β₂‐adrenoceptor affinity column and identified using quadrupole time‐of‐flight mass spectrometry. The affinity constants of the separated compounds that bind to β₂‐adrenoceptor were determined by frontal analysis. Compound bioactivity was tested in a rat tracheal smooth muscle relaxation assay. We identified the bioactive compounds in the water extract of Shaoyao‐Gancao decoction that bound to the β₂‐adrenoceptor as paeoniflorin and liquiritin. Paeoniflorin and liquiritin had only one binding site on the immobilized β₂‐adrenoceptor, and the affinity constants were (2.16 ± 0.10) × 10⁴ M⁻¹ and (2.95 ± 0.15) × 10⁴ M⁻¹, respectively. Both compounds induced a concentration‐dependent relaxation of tracheal smooth muscle following K⁺‐stimulated contraction, and the relaxation effects were abrogated by the β₂‐adrenoceptor antagonist, ICI 118551. Therefore, paeoniflorin and liquiritin are bioactive compounds in Shaoyao‐Gancao decoction and the β₂‐adrenoceptor affinity chromatography is a useful tool for identifying potential β₂‐adrenoceptor ligands in natural products used in traditional Chinese medicine.     

3β‐(Stearyloxy)olean‐12‐ene from Austroplenckia populnea: Structure Elucidation by 2D‐NMR and Quantitative 13C‐NMR Spectroscopy

3β‐(Stearyloxy)olean‐12‐ene was isolated from a hexane extract of Austroplenckia populnea Reiss (Celastraceae) leaves. The structure was solved by means of quantitative ¹³C‐NMR, HMBC, HMQC, COSY, NOESY, and NOE difference spectra. The mass spectrum showed an [M+1]⁺ ion peak at m/z 693, and the molecular formula C₄₈H₈₄O₂ was confirmed by combustion analysis.     

Identification of isomeric 5‐hydroxytryptophan‐ and oxindolylalanine‐containing peptides by mass spectrometry

Cells continuously produce reactive oxidative species that can modify all cellular components. In proteins, for example, cysteine, methionine, tryptophan (Trp), and tyrosine residues are particularly prone to oxidation. Here, we report two new approaches to distinguish two isomeric oxidation products of Trp residues, i.e. 5‐hydroxytryptophan (5‐HTP) and oxindolylalanine (Oia) residues, in peptides. First, 2‐nitrobenzenesulfenyl chloride, known to derivatize Trp residues in position 2 of the indole ring, was used to label 5‐HTP residues. The mass shift of 152.98 m/z units allowed identifying 5‐HTP‐ besides Trp‐containing peptides by mass spectrometry, whereas Oia residues were not labeled. Second, fragmentation of the Oia‐ and 5‐HTP‐derived immonium ions at m/z 175.08 produced ions characteristic for each residue that allowed their identification even in the presence of y₁ ions at m/z 175.12 derived from peptides with C‐terminal arginine residues. The pseudo MS³ spectra acquired on a quadrupole time‐of‐flight hybrid mass spectrometer displayed two signals at m/z 130.05 and m/z 132.05 characteristic for Oia‐containing peptides and a group of six signals (m/z 103.04, 120.04, 130.04, 133.03, 146.04, and 148.04) for 5‐HTP‐cointaining peptides. In both cases, the relative signal intensities appeared to be independent of the sequence providing a specific fingerprint of each oxidative modification. Copyright © 2012 John Wiley & Sons, Ltd.     

Sequence and phosphorylation level determination of two donkey β‐caseins by mass spectrometry

Two coeluting components, with experimentally measured M_r values of 25529 and 24606 Da, were identified by reversed‐phase high‐performance liquid chromatography (RP‐HPLC) and mass spectrometric analysis in the dephosphorylated casein fraction of a milk sample collected from an individual donkey belonging to the Ragusano breed of the east of Sicily. By coupling enzymatic digestions, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) and RP‐HPLC/nano‐electrospray ionization tandem mass spectrometry (nESI‐MS/MS) analysis, the two proteins were identified as donkey β‐CNs and their sequences characterized completely, using the two known β‐CNs from mare as references. The two donkey β‐CNs, showing a mass difference of 923 Da, differ by the presence of the domain E²⁷SITHINK³⁴ in the full‐length component (M_r 25529 Da). In comparison with the mare's β‐CNs used as reference, they present nine amino acid substitutions: L→S³⁷, R→H⁵², S→N⁸¹, P→V⁸⁴, L→V⁹¹, R→Q²⁰³, P→L/I²⁰⁶, L→F²¹⁰ and A→P²¹⁹. Together, these substitutions account for the increase of 18 Da in the M_r of the donkey β‐CNs with respect to the counterparts from the mare. The molecular mass determination by ESI‐MS for the phosphorylated proteins showed that the full‐length component was composed of highly multi‐phosphorylated isoforms with five to seven phosphate groups. By analogy with the homologous mare's β‐CNs, the full‐length (226 amino acids) β‐CN was termed variant A, whereas the shorter (218 amino acids) β‐CN was termed variant A^Δ5. Copyright © 2009 John Wiley & Sons, Ltd.     

Development of a CE‐MS2 method for the enantiomeric separation of L/D‐carnitine: Application to the analysis of infant formulas

A new chiral analytical method based on CE‐MS is proposed for the identification and simultaneous quantification of D /L ‐carnitine in infant formulas. Previous derivatization of carnitine with FMOC enabled the optimization of the chiral separation using CE with UV detection. An optimization of electrospray‐MS parameters using a partial filling of the non‐volatile chiral selector (succinyl‐γ‐CD) was performed. A selective fragmentation using MS² experiments with an ion trap analyser was carried out to confirm the identity of D /L ‐carnitine according to the current legislation. Satisfactory results were obtained in terms of linearity, precision, and accuracy. Interestingly, the CE‐MS² method developed allowed a sensitivity enhancement with respect to UV detection of 100‐fold, obtaining an LOD of 100 ng/g for D ‐carnitine. The determination of L ‐carnitine and its enantiomeric purity in 14 infant formulas supplemented with carnitine was successfully achieved, sample preparation only requiring an ultrafiltration with centrifugal filter devices to retain the components with the highest molecular weights.     

Sequence determination of αs1‐casein isoforms from donkey by mass spectrometric methods

Four co‐eluting components, with experimentally measured M_r of 23 658, 23 786, 24 278 and 24 406 Da, were detected by reversed‐phase high‐performance liquid chromatography (RP‐HPLC) and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) analysis in the dephosphorylated casein fraction of a milk sample collected at middle lactation stage from an individual donkey belonging to the Ragusano breed. By coupling RP‐HPLC, two‐dimensional polyacrylamide gel electrophoresis (2D‐PAGE), enzymatic digestions, MALDI‐TOF MS and capillary RP‐HPLC/nano‐electrospray ionization tandem mass spectrometry (nESI‐MS/MS) analyses, the four components were identified as donkey's α_s1‐CNs and their sequences completely characterized, using the known mare's α_s1‐CN (GenBank Acc. No. AAK83668; M_r 23750.7 Da) as reference. The proteins with M_r of 23 786 and 23 658 Da differ in the presence of a glutamine residue at position 83 in the full‐length component and present the amino acid substitutions Q⁸→H and H¹¹⁵→Y with respect to the mare's α_s1‐CN. The other two components with M_r 24 406 and 24 278 Da, which also differ in the presence of a glutamine residue at position 88 in the full‐length component, show the insertion of the pentapeptide HTPRE between Leu³³ and the Glu³⁴. The two α_s1‐CNs bearing the pentapeptide insertion were named variants A (202 amino acids; M_r 24 406) and A₁ (201 amino acids; M_r 24 278), whereas the two α_s1‐CNs without the pentapeptide were named variants B (197 amino acids; M_r 23 786) and B₁ (196 amino acids; M_r 23 658). Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of block and end‐functionalized polyesters by triflimide‐catalyzed ring‐opening polymerization of ε‐caprolactone, 1,5‐dioxepan‐2‐one,and rac‐lactide

The ring‐opening polymerization (ROP) of cyclic esters, such as ε‐caprolactone, 1,5‐dioxepan‐2‐one, and racemic lactide using the combination of 3‐phenyl‐1‐propanol as the initiator and triflimide (HNTf₂) as the catalyst at room temperature with the [monomer]₀/[initiator]₀ ratio of 50/1 was investigated. The polymerizations homogeneously proceeded to afford poly(ε‐caprolactone) (PCL), poly(1,5‐dioxepan‐2‐one) (PDXO), and polylactide (PLA) with controlled molecular weights and narrow polydispersity indices. The molecular weight determined from an ¹H NMR analysis (PCL, M_n,NMR = 5380; PDXO, M_n,NMR = 5820; PLA, M_n,NMR = 6490) showed good agreement with the calculated values. The ¹H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry analyses strongly indicated that the obtained compounds were the desired polyesters. The kinetic measurements confirmed the controlled/living nature for the HNTf₂‐catalyzed ROP of cyclic esters. A series of functional alcohols, such as propargyl alcohol, 6‐azido‐1‐hexanol, N‐(2‐hydroxyethyl)maleimide, 5‐hexen‐1‐ol, and 2‐hydroxyethyl methacrylate, successfully produced end‐functionalized polyesters. In addition, poly(ethylene glycol)‐block‐polyester, poly(δ‐valerolactone)‐block‐poly(ε‐caprolactone), and poly(ε‐caprolactone)‐block‐polylactide were synthesized using the HNTf₂‐catalyzed ROP. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2455–2463     

Identification of bioactive peptides in hypoallergenic infant milk formulas by capillary electrophoresis-mass spectrometry

In this study, we use capillary electrophoresis-mass spectrometry (CE-MS) for the identification of bioactive peptides in hypoallergenic infant milk formulas (IF), which are complex bovine milk protein hydrolysates. A sample clean-up pretreatment with a citrate buffer containing dithiothreitol and urea followed by solid-phase extraction (SPE) with different reversed-phase commercial cartridges was investigated to achieve optimum detection sensitivity in CE-MS. SPE with C18, StrataX and Oasis HLB cartridges allowed detection of the largest number of low molecular mass components, but combination of C18 and StrataX results was enough to achieve an excellent coverage of the studied IF. The monoisotopic molecular mass values of the low molecular mass components obtained by capillary electrophoresis ion-trap mass spectrometry (CE-IT-MS) allowed the tentative identification of nine bioactive sequences. Only the identification of five of them could be confirmed when accurate mass measurements were performed by capillary electrophoresis time-of-flight mass spectrometry (CE-TOF-MS), namely LKP, IPY, ALPM, PGPIHN and VAGTWY, which were reported to present angiotensin-converting enzyme (ACE) inhibitory and antimicrobial activity (only VAGTWY).     

An update for human blood plasma pretreatment for optimized recovery of low‐molecular‐mass peptides prior to CE–MS and SPE–CE–MS

Protein precipitation and centrifugal filtration are well‐established methods for concentrating and purifying peptides with a low relative molecular mass (M_r) from human blood plasma before proteomic and peptidomic studies using high‐performance separation techniques, but there is little information on peptide recoveries. Here, we evaluate acetonitrile precipitation followed by a range of centrifugal filtration conditions for the analysis of low M_r peptides in human blood plasma before CE–MS and SPE coupled online to CE–MS. Three opioid peptides were used as model compounds, that is, dynorphin A 1–7, endomorphin 1, and methionine enkephalin and 3, 10, and 30 K M_r cut‐off cellulose acetate filters (Amicon® Ultra‐0.5) and 10 K M_r cut‐off polyethersulfone filters (Vivaspin® 500) were studied. Unexpectedly, recoveries and repeatability were only optimum after passivating the 10 K M_r cut‐off cellulose acetate filters with PEG to avoid peptide adsorption on the inner walls of the plastic sample reservoir.     

Characterization of N‐methylated amino acids by GC‐MS after ethyl chloroformate derivatization

Methylation is an essential metabolic process in the biological systems, and it is significant for several biological reactions in living organisms. Methylated compounds are known to be involved in most of the bodily functions, and some of them serve as biomarkers. Theoretically, all α‐amino acids can be methylated, and it is possible to encounter them in most animal/plant samples. But the analytical data, especially the mass spectral data, are available only for a few of the methylated amino acids. Thus, it is essential to generate mass spectral data and to develop mass spectrometry methods for the identification of all possible methylated amino acids for future metabolomic studies. In this study, all N‐methyl and N,N‐dimethyl amino acids were synthesized by the methylation of α‐amino acids and characterized by a GC‐MS method. The methylated amino acids were derivatized with ethyl chloroformate and analyzed by GC‐MS under EI and methane/CI conditions. The EI mass spectra of ethyl chloroformate derivatives of N‐methyl ( 1–18 ) and N,N‐dimethyl amino acids ( 19–35 ) showed abundant [M‐COOC₂H₅]⁺ ions. The fragment ions due to loss of C₂H₄, CO₂, (CO₂ + C₂H₄) from [M‐COOC₂H₅]⁺ were of structure indicative for 1–18 . The EI spectra of 19–35 showed less number of fragment ions when compared with those of 1–18 . The side chain group (R) caused specific fragment ions characteristic to its structure. The methane/CI spectra of the studied compounds showed [M + H]⁺ ions to substantiate their molecular weights. The detected EI fragment ions were characteristic of the structure that made easy identification of the studied compounds, including isomeric/isobaric compounds. Fragmentation patterns of the studied compounds ( 1–35 ) were confirmed by high‐resolution mass spectra data and further substantiated by the data obtained from ¹³C₂‐labeled glycines and N‐ethoxycarbonyl methoxy esters. The method was applied to human plasma samples for the identification of amino acids and methylated amino acids. Copyright © 2016 John Wiley & Sons, Ltd.     

Bioactivity‐integrated ultra‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry for the identification of nuclear factor‐κB inhibitors and β2 adrenergic receptor agonists in Chinese medicinal preparation Chuanbeipipa dropping pills

A simple and dual‐target method based on ultra‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry combined with dual‐bioactive [nuclear factor‐κB (NF‐κB) and β₂‐adrenergic receptor] luciferase reporter assay systems was developed to rapidly characterize the chemical structure of various bioactive compounds of TCM preparations. Chuanbeipipa dropping pills, a traditional Chinese medicine preparation used for the clinical therapy of chronic obstructive lung disease and cough caused by bronchial catarrh, was analyzed with this method. Potential anti‐inflammatory and spasmolytic constituents were screened using NF‐κB and β₂‐adrenergic receptor activity luciferase reporter assay systems and simultaneously identified according to the time‐of‐flight mass spectrometry data. One β₂‐adrenergic receptor agonist (ephedrine) and two structural types of NF‐κB inhibitors (platycosides derivatives and ursolic acid derivatives) were characterized. Platycodin D3 and E were considered new NF‐κB inhibitors. Further cytokine and chemokine detection confirmed the anti‐inflammatory effects of the potential NF‐κB inhibitors. Compared with conventional fingerprints, activity‐integrated fingerprints that contain both chemical and bioactive details offer a more comprehensive understanding of the chemical makeup of plant materials. This strategy clearly demonstrated that multiple bioactivity‐integrated fingerprinting is a powerful tool for the improved screening and identification of potential multi‐target lead compounds in complex herbal medicines. Copyright © 2013 John Wiley & Sons, Ltd.     

Quantification of peptides using N‐terminal isotope coding and C‐terminal derivatization for sensitive analysis by micro liquid chromatography‐tandem mass spectrometry

Stable isotope‐coding coupled with mass spectrometry is a popular method for quantitative proteomics and peptide quantification. However, the efficiency of the derivatization reaction at a particular functional group, especially in complex structures, can affect accuracy. Here, we present a dual functional‐group derivatization of bioactive peptides followed by micro liquid chromatography‐tandem mass spectrometry (LC‐MS/MS). By separating the sensitivity‐enhancement and isotope‐coding derivatization reactions, suitable chemistries can be chosen. The peptide amino groups were reductively alkylated with acetaldehyde or acetaldehyde‐d₄ to afford N‐alkylated products with different masses. This process is simple, quick and high‐yield, and accurate comparative analysis can be achieved for the mass‐differentiated peptides. Then, the carboxyl groups were derivatized with 1‐(2‐pyrimidinyl)piperazine to increase MS/MS sensitivity. Angiotensins I–IV, bradykinin and neurotensin were analyzed after online solid phase extraction by micro LC‐MS/MS. In all instances, a greater than 17‐fold increase in sensitivity was achieved, compared with the analyses of the underivatized peptides. Furthermore, the values obtained from the present method were in agreement with the result from isotope dilution quantification using isotopically labeled angiotensin I [Asp‐Arg‐(Val‐d₈)‐Tyr‐Ile‐His‐Pro‐(Phe‐d₈)‐His‐Leu]. Copyright © 2016 John Wiley & Sons, Ltd.     

Polymethylene‐block‐polystyrene copolymers: A new synthetic approach using a combination of polyhomologation and reversible addition‐fragmentation chain‐transfer polymerization and their microfibers and microspheres fabricated through electrospinning process

Well‐defined polymethylene‐block‐polystyrene (PM‐b‐PS) diblock copolymers were synthesized via a combination of polyhomologation of ylides and reversible addition‐fragmentation chain‐transfer (RAFT) polymerization of styrene. Trithiocarbonate‐terminated polymethylenes (PM‐TTCB) (M_n = 1400 g mol^?1; M_w/M_n = 1.09 and M_n = 2100 g mol^?1; M_w/M_n = 1.20) were obtained via an esterification of S?1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐acetate) trithiocarbonate with hydroxyl‐terminated polymethylene synthesized via polyhomologation of ylides followed by oxidation. Then, a series of PM‐b‐PS (M_n = 5500–34,000 g mol^?1; M_w/M_n = 1.12–1.25) diblock copolymers were obtained by RAFT polymerization of styrene using PM‐TTCB as a macromolecular chain‐transfer agent. The chain structures of all the polymers were characterized by proton nuclear magnetic resonance (¹H NMR), gel permeation chromatography, and Fourier transform infrared spectroscopy. The thiocarbonylthio end‐group of PM‐b‐PS was transformed into thiol group by aminolysis and confirmed by UV–vis spectroscopy. In addition, microfibers and microspheres of such diblock copolymers were fabricated by electrospinning process and observed by scanning electron microscopy (SEM). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2892–2899     

Determination of block size in poly(ethylene oxide)‐b‐polystyrene block copolymers by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

Characterization of block size in poly(ethylene oxide)‐b‐poly(styrene) (PEO‐b‐PS) block copolymers could be achieved by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) after scission of the macromolecules into their constituent blocks. The performed hydrolytic cleavage was demonstrated to specifically occur on the targeted ester function in the junction group, yielding two homopolymers consisting of the constitutive initial blocks. This approach allows the use of well‐established MALDI protocols for a complete copolymer characterization while circumventing difficulties inherent to amphiphilic macromolecule ionization. Although the labile end‐group in PS homopolymer was modified by the MALDI process, PS block size could be determined from MS data since polymer chains were shown to remain intact during ionization. This methodology has been validated for a PEO‐b‐PS sample series, with two PEO of number average molecular weight (M_n) of 2000 and 5000 g mol^?1 and M_n(PS) ranging from 4000 to 21,000 g mol^?1. Weight average molecular weight (M_w), and thus polydispersity index, could also be reached for each segment and were consistent with values obtained by size exclusion chromatography. This approach is particularly valuable in the case of amphiphilic copolymers for which M_n values as determined by liquid state nuclear magnetic resonance might be affected by micelle formation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3380–3390, 2009     

Systematic characterization of the covalent interactions between (−)‐epigallocatechin gallate and peptides under physiological conditions by mass spectrometry

(?)‐Epigallocatechin gallate (EGCG) is a major bioactive component in leaves of green tea, and has been widely investigated for its anti‐tumor activity. The interaction between EGCG and the key peptides or proteins (e.g. glutathione, enzymes) in vivo is thought to be involved in the toxicity and anti‐cancer mechanism of EGCG. However, the true anti‐tumor mechanism of EGCG is not clear, and few studies have focused on the reactivity of EGCG toward peptides or proteins under physiological conditions (pH 7.4, 37°C). In this work, the covalent interactions between EGCG and model peptides containing one or more nucleophilic residues (i.e. Arg, Cys, Met, and α‐NH₂ of the N‐terminus of peptides) under physiological condition were fully characterized using mass spectrometry. It was found that EGCG can react with the thiol groups of peptides to form adducts under physiological conditions (pH 7.4, 37°C), even in the absence of the peroxidase/hydrogen peroxide system. Besides the thiol groups of peptides, it is firstly reported that EGCG also reacts with α‐NH₂ of the N‐terminus or arginine residues of model peptides to form Schiff base adducts, and the methionine residues of model peptides can be easily oxidized by hydrogen peroxide (H₂O₂) generated during the process of EGCG auto‐oxidation to form methionine sulfoxide products. The preference for the reaction of nucleophlic residues of peptides with EGCG was determined to have the following order: Cys > α‐NH₂ of the N‐terminus > Arg. The neutral loss ions of [M+H–170]⁺ and [M+H‐138]⁺ were detected in all tandem mass spectra of the EGCG adducts of peptides, which indicates that these two neutral loss ions can be considered as the characteristic neutral loss ions of peptides modified by EGCG. Results of the present research provide insights into the toxicology and anti‐tumor mechanism of EGCG in vivo. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of three‐armed poly(trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L‐proline)‐block‐poly(ε‐caprolactone) copolymers

A series of novel types of three‐armed poly(trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline)‐block‐poly(ε‐caprolactone) (PHpr‐b‐PCL) copolymers were successfully synthesized via melt block copolymerization of trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline (N‐CBz‐Hpr) and ε‐caprolactone (ε‐CL) with a trifunctional initiator trimethylolpropane (TMP) and stannous octoate (SnOct₂) as a catalyst. For the homopolycondensation of N‐CBz‐Hpr with TMP initiator and SnOct₂ catalyst, the number‐average molecular weight (M_n) of prepolymer increases from 530 to 3540 g mol^?1 with the molar ratio of monomer to initiator (3–30), and the molecular weight distribution (M_w/M_n) is between 1.25 to 1.32. These three‐armed prepolymer PHpr were subsequently block copolymerized with ε‐caprolactone (ε‐CL) in the presence of SnOct₂ as a catalyst. The M_n of the copolymer increased from 2240 to 18,840 g mol^?1 with the molar ratio (0–60) of ε‐CL to PHpr. These products were characterized by differential scanning calorimetry (DSC), ¹H NMR, and gel permeation chromatography. According to DSC, the glass‐transition temperature (T_g) of the three‐armed polymers depended on the molar ratio of monomer/initiator that were added. In vitro degradation of these copolymers was evaluated from weight‐loss measurements and the change of M_n and M_w/M_n. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1708–1717, 2005     

Boron‐functionalized poly(3‐hydroxybutyrate)s from hydroboration of poly(allyl‐β‐hydroxyalkanoate)s: Synthesis and insights into the microstructure

The controlled ring‐opening polymerization of racemic allyl‐β‐butyrolactone (rac‐BL^allyl) in toluene or in bulk, catalyzed by the discrete β‐diiminate zinc amido [(BDI^iPr)Zn(N(SiMe₃)₂)] ( 1 ) or {amino‐methoxy‐bis(phenolate)}yttrium amido [(ONOO^tBu)Y(N(SiHMe₂)₂)(THF)] ( 2 ) complexes, in association with an alcohol, gave poly(β‐hydroxyalkanoate)s (PHAs) with allylic side chains. These PHAs^allyl exhibit either a slightly isotactic‐enriched (P_m = 0.61) or highly syndiotactic‐enriched (P_r = 0.82) backbone structure, respectively, with high molar mass (M _n up to 21,100 g mol^?1) and narrow molar mass distribution values (1.05 < M _w/M _n < 1.28), as evidenced by detailed ¹³C NMR and size exclusion chromatography analyses. Postpolymerization rhodium‐catalyzed hydroboration of the resulting PHAs^allyl with pinacolborane quantitatively afforded the corresponding PHAs^boron. Introduction of boron into the pendant chains did not alter neither the structure of the polymer backbone nor the macromolecular features (M _n, M _w/M _n, and stereoregularity). However, differential scanning calorimetry analyses revealed a significant increase of the glass transition temperature on modifying the allyl for the boron function in these PHAs. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

End‐functionalization of polystyrene by malto‐oligosaccharide generating aggregation‐tunable polymeric reverse micelle

This article describes that glucose, maltose, maltotriose, maltotetraose, maltopentaose, and maltohexaose ( a , b , c , d , e , and f , respectively) were introduced into the initiating chain‐end of polystyrene (PSt) through the 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO)‐mediated radical polymerization. A series of glycoconjuaged TEMPO‐adducts, 1a–f , was synthesized and used as the initiators for the polymerization of styrene (St) for 6 h at 120 °C to afford the end‐functionalized PSt's with the acetyl saccharides, 2a–f , in the yields of 37–43%. For 2a–f obtained by the polymerizations using the [St]/[ 1 ] of 125, 250, and 500, the number‐average molecular weights determined by size exclusion chromatography (SEC), M_n,SEC's, were 4800–6300, 8800–10,600, and 18,400–25,200, respectively, which fairly agreed with the predicted values. The end‐functionalized PSt's with saccharides, 3a–f , which were obtained from the deacetylation of 2a–f using sodium methoxide in dry THF, formed the polymeric reverse micelles consisting of a saccharide‐core and a PSt‐shell in chloroform and toluene. The static laser light scattering (SLS) measurements provided the average molar mass of the aggregates in toluene, M_w,SLS's, which ranged from 7.50 × 10⁴ to 1.77 × 10⁵ for 3a , from 1.90 × 10⁵ to 4.93 × 10⁵ for 3b , from 4.41 × 10⁵ to 7.21 × 10⁵ for 3c , from 5.85 × 10⁵ to 8.51 × 10⁵ for 3d , from 7.55 × 10⁵ to 8.53 × 10⁵ for 3e , and from 8.54 × 10⁵ to 9.26 × 10⁵ for 3f . The aggregation numbers, N_agg's, which were calculated from the M_w,SLS's, were from 7 to 24 for 3a , from 20 to 37 for 3b , from 34 to 89 for 3c , from 39 to 116 for 3d , from 41 to 145 for 3e , and from 31 to 146 for 3f . It was confirmed that the aggregation property, such as the M_w,SLS or N_agg values, was strongly related to the polymerization degrees of St (DP's) or the number of the glucose residues (n's) for 3a–f . © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4864–4879, 2006     

Easy synthesis and ring‐opening polymerization of 5‐Z‐amino‐δ‐valerolactone: New degradable amino‐functionalized (Co)polyesters

Novel 5‐Z‐amino‐δ‐valerolactone (5‐NHZ‐VL) was synthesized with an aim to prepare degradable polyesters and copolyesters having amino pendant groups. Following a straightforward and efficient synthetic pathway, 5‐NHZ‐VL was obtained in only two steps and up to 50% yield. The monomer was fully characterized by ¹H NMR, ¹³C NMR, ESI mass spectrometry, and HPLC. Various conventional conditions were tested for this lactone ring‐opening polymerization and led to the novel corresponding poly(5‐NHZ‐VL) (M_n = 7000 g/mol; PD = 1.2). Following this homopolymerization, 5‐NHZ‐VL was copolymerized with ε‐caprolactone to generate a family of copolyesters with an amino‐group content ranging from 10 to 80%. Finally, the polyelectrolyte poly(5‐NH₃⁺‐VL) was recovered by removal of the protecting group under acidic conditions, and integrity of the polyester backbone was confirmed by ¹H NMR. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Mononuclear Complexes of Platinum Group Metals Containing η6‐ and η5‐Cyclic Π‐Perimeter Hydrocarbon and Pyridylpyrazolyl Derivatives: Syntheses and Structural Studies

Piano‐stool‐shaped platinum group metal compounds, stable in the solid state and in solution, which are based on 2‐(5‐phenyl‐1H‐pyrazol‐3‐yl)pyridine ( L ) with the formulas [(η⁶‐arene)Ru( L )Cl]PF₆ {arene = C₆H₆ ( 1 ), p‐cymene ( 2 ), and C₆Me₆, ( 3 )}, [(η⁶‐C₅Me₅)M( L )Cl]PF₆ {M = Rh ( 4 ), Ir ( 5 )}, and [(η⁵‐C₅H₅)Ru(PPh₃)( L )]PF₆ ( 6 ), [(η⁵‐C₅H₅)Os(PPh₃)( L )]PF₆ ( 7 ), [(η⁵‐C₅Me₅)Ru(PPh₃)( L )]PF₆ ( 8 ), and [(η⁵‐C₉H₇)Ru(PPh₃)( L )]PF₆ ( 9 ) were prepared by a general method and characterized by NMR and IR spectroscopy and mass spectrometry. The molecular structures of compounds 4 and 5 were established by single‐crystal X‐ray diffraction. In each compound the metal is connected to N1 and N11 in a k² manner.