Polymeric cinchona alkaloids for the catalytic asymmetric dihydroxylation of olefins

Three cinchona alkaloid copolymers (PMMA‐BQTP, PMA‐BQTP, PAN‐BQTP) have been synthesized by copolymerization. Their structure was characterized by FTIR, GPC, and element analysis. The catalytic activity of these copolymers in asymmetric dihydroxylation (AD) of olefins by OsO₄ was studied. The products enantiomeric excesses (ee) and the conversion of the substrate in the dihydroxylation reactions were determined using HPLC. The effect of time, temperature, and recycle times on the reaction was also discussed. The results showed that the copolymers catalyzed the dihydroxylation of the olefins to get diols in high optical yield. However, their catalytic efficiency was largely depended on the nature of olefins. The polymeric cinchona alkaloid can be simply recovered at the end of the reaction by centrifugation and then reused without radical change of activity or enantioselectivity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Photocurable biodegradable polyesters from poly(L‐lactide) diols

α,ω‐Dihydoxy‐terminated poly(L ‐lactide)s (PLLA diols) with various molecular weights (1000, 2000 and 3000 g mol^?1) were prepared by the ring‐opening polymerization of L ‐lactide using 1,6‐hexanediol as an initiator. These were subsequently chain‐extended with the diacyl chloride of 4,4′‐(adipoyldioxy)dicinnamic acid (CAC) to obtain high‐molecular‐weight photocurable polyesters (CAC/PLLAs). The resulting polyesters were characterized by gel permeation chromatography, Fourier‐transform infrared, ultraviolet–visible and proton nuclear magnetic resonance spectroscopies, differential scanning calorimetry and thermogravimetry. These photoreactive polyesters were irradiated with a high‐pressure mercury lamp (λ > 280 nm) for 30–180 min to produce the crosslinked polyesters. The gel fraction yield increased with photocuring time, and exceeded 80 % after 180 min. The photocuring process disturbed the crystallization of the CAC/PLLA films, while it enhanced their thermal stabilities. With increasing photocuring time, both the tensile strength and modulus increased markedly. The best mechanical properties (tensile strength = 41 MPa; tensile modulus = 1550 MPa) were obtained for a CAC/PLLA‐3000 film photocured for 180 min. The tensile modulus of this photocured film was larger than that of pure PLLA. The hydrolytic degradation rates of the CAC/PLLA films in a phosphate buffer solution (pH, 7.2) of proteinaze‐k at 37 °C were much slower than those of pure PLLA films. Copyright © 2004 Society of Chemical Industry     

Enantioselective Biooxidation of Racemic trans‐Cyclic Vicinal Diols: One‐Pot Synthesis of Both Enantiopure (S,S)‐Cyclic Vicinal Diols and (R)‐α‐Hydroxy Ketones

Highly regio‐ and enantioselective alcohol dehydrogenases BDHA (2,3‐butanediol dehydrogenase from Bacillus subtilis BGSC1A1), CDDHPm (cyclic diol dehydrogenase from Pseudomonas medocina TA5), and CDDHRh (cyclic diol dehydrogenase from Rhodococcus sp. Moj‐3449) were discovered for the oxidation of racemic trans‐cyclic vicinal diols. Recombinant Escherichia coli expressing BDHA was engineered as an efficient whole‐cell biocatalyst for the oxidation of (±)‐1,2‐cyclopentanediol, 1,2‐cyclohexanediol, 1,2‐cycloheptane‐diol, and 1,2‐cyclooctanediol, respectively, to give the corresponding (R)‐α‐hydroxy ketones in >99% ee and (S,S)‐cyclic diols in >99% ee at 50% conversion in one pot. Escherichia coli (BDHA‐LDH) co‐expressing lactate dehydrogenase (LDH) for intracellular regeneration of NAD⁺ catalyzed the regio‐ and enantioselective oxidation of (±)‐1,2‐dihydroxy‐1,2,3,4‐tetrahydronaphthalene to produce the corresponding (R)‐α‐hydroxy ketone in >99% ee and (S,S)‐cyclic diol in 96% ee at 49% conversion. Preparative biotransformations were also demonstrated. Thus, a novel and useful method for the one‐pot synthesis of both vicinal diols and α‐hydroxy ketones in high ee was developed via highly regio‐ and enantioselective oxidations of the racemic vicinal diols.

     

脂肪族聚碳酸酯的研究进展

综述了通过环氧化物与CO2共聚法、脂肪族环状碳酸酯开环聚合法及脂肪族二元醇与碳酸二烃基酯聚合法合成脂肪族聚碳酸酯(APCs)的研究进展,特别是对各种反应体系所采用催化剂的突破性研究成果进行了介绍,并对反应机理进行了分析。讨论了APCs的结构与其生物降解性及热分解性等性能的关系;结合APCs的性质介绍了它在医用材料、陶瓷及橡胶工业等领域的应用。比较了合成APCs的不同途径的特点,并对APCs材料的合成方法及其应用的发展趋势进行了展望。     

显色剂ABBPDT与汞的显色反应及其应用

在pH为11.5的Na2B4O7-NaOH缓冲溶液中,OP表面活性剂存在下,1-偶氮苯-3-(5-溴-2-吡啶)-三氮烯(ABBPDT)与汞发生显色反应,生成2∶1型红色配合物。配合物的最大吸收峰520nm,表观摩尔吸光系数为1.81×105L/(mol·cm)。用拟定方法测定废水中的微量汞,Hg2+质量浓度在0￣480μg/L符合比尔定律,结果满意。     

Insights into the Molecular Recognition Process in Organocatalytic Chemoselective Monoacylation of 1,5‐Pentanediol

Monoacylation of long‐chain linear diols often encounters difficulties associated with unavoidable overacylation affording the diacylate. However, several C₁‐ and C₂‐symmetrical pyrrolidinopyridine (PPY) catalysts were found to effectively promote the chemoselective monoacylation of 1,5‐pentanediol. The effects of catalyst structure on the performance for the monoacylation were investigated. The amide carbonyl group(s) in the pyrrolidine ring in both C₁‐ and C₂‐symmetrical catalysts was(were) suggested to play the key role in selective monoacylation. On the other hand, the indolyl NH group in the amide side chain of the catalysts was found to be critically important for further increasing the chemoselectivity of monoacylation only when the catalyst has a C₂‐symmetrical structure. The effects of the catalyst structure on the chemoselective monoacylation were elucidated by DFT calculations, and the origin of the precise molecular recognition for 1,5‐pentanediol by the catalysts and transition state (TS) stabilization effects by these functionalities were disclosed.

     

1—（6—硝基—2—苯并噻唑）—3—（4—硝基苯）—三氮烯与镉的显色反应研究

研究表明,新显色剂1-(6-硝基-2-苯并噻唑)-3-(4-硝基苯)-三氮烯与镉反应,可生成稳定的橙黄色络合物,分别在444nm和530nm波长处有一正一负两个吸收峰,建立以530nm为参比波长,444nm为测定波长的双峰双波长测定法,表观摩尔吸光系数达2.82×105,镉含量在0～280μg/L符合比尔定律,测定了实验室废水和人发中的镉含量,结果满意.     

三氮烯试剂析相光度法测定痕量铜的研究

研究了三氮烯试剂 -铜 -OP乳化剂析相富集体系在Na2 B4O7-NaOH( pH10.2 )介质中 ,于 90± 1℃加热胶束溶液 ,保持 45min ,络合物即被OP乳化剂完全富集。富集液在 5 2 0nm处测定吸光度 ,铜含量在 0～ 3 0 μg/5 0mL范围内服从比尔定律 ,该法与一般光度法相比 ,灵敏度高 ,选择性好。用于铝合金样中铜的测定 ,结果满意。     

1-(间硝基苯基)-3-(2-氨基噻唑)三氮烯与钯(Ⅱ)的显色反应及其分析应用

研究了一个新的三氮烯类试剂：１－（间硝基苯基）３－（２－氨基噻唑）三氮烯（ｍ－ＮＰＡＴＴ）,在Ｔｗｅｅｎ８０存在下与钯（Ⅱ）显色反应。结果表明,在ＰＨ８．０－１０．０范围内,钯（Ⅱ）与ｍ－ＮＰＡＴＴ形成１：２的稳定络合物,其表观摩尔吸光系数在４７５ｎｍ处为６．８２＊１０＾４。钯量在０．１０－１０．０μｇ／１０ｍＬ范围内符合比尔定律。对３０多种共存离子进行试验,除Ｃｕ＾２＋,Ａｇ＾２＋,Ｃｄ＾２＋,Ｈｇ＾２＋稍有干扰外,其余离子均不干扰测定,用该方法测定了催化剂中钯的含量,结果满意。