一种改进的由氨基酸酯制备手性氨基醇的新方法

采用NaBH4/CeCl3作为还原体系,在无水甲醇溶剂中,将氨基酸甲酯还原为相应的手性氨基醇。以L-苯丙氨酸甲酯还原制备L-苯丙氨醇的反应为研究对象,考察了催化剂用量、反应温度及时间诸因素对产品收率的影响。结果表明:在n(L-苯丙氨酸甲酯)∶n(CeCl3)=1∶2、反应温度30℃、反应时间2 h的优化条件下,L-苯丙氨醇收率为90.3%。本法有操作简便,收率高等优点,该反应为制备手性氨基醇提供了一种新的有用的合成方法。     

N-甲基-L-苯丙氨酸甲酯的合成

以L-苯丙氨酸为初始原料,先与甲醇成酯反应,再与苯甲醛反应形成希夫碱中间体,经过Pd/C催化氢化,再与多聚甲醛反应,最后经氢化还原与脱苄基得到光学纯N-甲基-L-苯丙氨酸甲酯,总收率为83.1%。该工艺反应条件温和,无需对氨基酸的侧链进行保护,收率高,适合工业化生产。     

L-苯丙氨酸甲酯化反应(Ⅱ)——L-苯丙氨酸甲酯化反应动力学

根据一般羧酸酯化反应的基元过程和广义酸催化理论 ,假定催化剂氢离子与酰基氧结合的过程为控制步骤 ,导出了一个 L-苯丙氨酸的甲酯化反应动力学方程 ,该方程预测值与实验结果吻合良好。     

L-4-硝基苯丙氨酸的合成研究

L-4-硝基苯丙氨酸为合成众多药物的中间体.采用釜式反应器,以混酸(浓硫酸与浓硝酸)为硝化试剂对L-苯丙氨酸进行硝化反应,制备得到了目标产物.在浓硫酸与浓硝酸的体积比为2:1,反应温度为0℃,反应时间为3 h的工艺条件下,该法制备L-4-硝基苯丙氨酸的收率达到65.2%.该法在反应过程中得到的副产物,经~1H-NMR和~(13)C-NMR鉴定了其结构,证明其为两分子间的缩合产物,据此推测了反应可能的机理.为了减少分子间的缩合反应,采用管式反应器对苯丙氨酸的硝化反应进行探索,并用正交实验法对反应条件进行了优化,结果表明,反应温度为50℃,反应时间为5 min,混酸中浓硫酸与浓硝酸体积比为2:1,收率可达80.9%.与釜式反应相比,管式反应器能够有效避免分子间缩合的副反应,并能加快反应速率,提高反应效率.     

L-苯丙氨酸参与的Amadori化合物的合成及其在卷烟中的应用

研究了L-苯丙氨酸参与的Amadori化合物的合成反应条件,及该产物对卷烟吸味的影响。结果表明,用乙醇、丙二醇作溶剂,D-木糖或D-果糖作反应物,反应物配比为1∶3所得的Amadori产物对烟草的作用效果较明显。利用裂解-气/质联用仪（PYROLYSIS-GC/MS）测定了L-苯丙氨酸与木糖反应生成的Amadori化合物在300℃下裂解产生的多种致香成分,证实了L-苯丙氨酸与还原糖生成的Amadori化合物能改善卷烟制品的抽吸效果。     

L-苯丙氨酸甲酯消旋反应改进

对L-苯丙氨酸甲酯消旋方法进行改进。研究了L-苯丙氨酸甲酯在不同催化剂、催化剂用量、反应时间下的消旋制备DL-苯丙氨酸甲酯过程。结果表明:当以水杨醛为催化剂、强酸性D072离子交换树脂为助催化剂、n(水杨醛)∶n(L-苯丙氨酸甲酯)=0.1回流反应时,消旋效果最好。     

L-抗坏血酸硬脂酸酯的合成条件探索

文章对L-抗坏血酸硬脂酸酯的最佳合成条件进行探索。通过各种不同的实验条件得出最佳合成条件为：抗坏血酸比硬脂酸甲醣为1：1．3（摩尔比）,催化剂浓硫酸比（抗坏血酸＋硬脂酸甲酪）为1：0．10（摩尔比）,反应温度24℃,反应时闯24h。在此条件下可获得总产率为77％的抗坏血酸硬脂酸酯。考察了以硬脂酸甲酯和L-抗坏血酸为原料,通过酯交换法合成L-抗坏血酸硬脂酸酯的最佳合成条件。文章对L-抗坏血酸硬脂酸酯的最佳合成条件进行探索。通过各种不同的实验条件得出最佳合成条件为：抗坏血酸比硬脂酸甲酯为1：1.3（摩尔比）,催化剂浓硫酸比（抗坏血酸＋硬脂酸甲酯）为1：0．10（摩尔比）,反应温度24℃,反应时间24h。在此条件下可获得总产率为77％的抗坏血酸硬脂酸酯。考察了以硬脂酸甲酯和L-抗坏血酸为原料,通过酯交换法合成L-抗坏血酸硬脂酸酯的最佳合成条件。     

手性氨基醇的绿色催化工艺研究

以L-丙氨酸为原料,利用5%钌-铑/氧化铝双金属催化加氢还原得到L-丙氨醇,其催化加氢工艺优化得到当磷酸与丙氨酸的摩尔比为1.1、反应温度110℃、反应时间7h、反应压力4MPa时,L-丙氨酸的转化率为96%,得到L-丙氨醇的光学收率为99%.该方法也适用于L-苯丙氨酸、L-缬氨酸等氨基酸的催化加氢,光学收率均为97%以上.     

微波促L-苯丙氨酸消旋反应研究

介绍了微波促L-苯丙氨酸消旋反应是一种新的可适合于工业化的生产方法，具有对环境友好的优点。使用微波作为热源不仅可加速反应和节约能源，也可提高反应的收率和产品的纯度。本方法确定了在微波辐射下，以1．0mol／L氢氧化钠水溶液替代低级脂肪酸作为反应溶剂，用物质的量比为0．10的水杨醛为催化剂，L-苯丙氨酸可以快速消旋；在此务件下，消旋反应随微波辐射功率的提高而加快，在66％输出功率下反应已接近最大反应速率。从实验中得出微波促L-苯丙氨酸消旋的反应是一级不可逆反应。考察了此消旋反应的影响因素，同时讨论了微波作用下L-苯丙氨酸的消旋反应机理。     

HPLC法测定L-丙氨酸甲酯盐酸盐中L-丙氨酸含量

建立了HPLC法分离测定L-丙氨酸甲酯盐酸盐中L-丙氨酸含量。色谱条件为:Shim-packVP-ODS柱(150mm×4.6mm,5μm);流动相为甲醇-NaH2PO4水溶液,NaH2PO4溶液浓度为0.05mol·L-1、pH值为6.50(H3PO4调节),甲醇与NaH2PO4溶液体积比为1∶9;流速0.80mL·min-1;柱温为30℃;检测波长为210nm;进样量5μL。该方法的建立为L-丙氨酸甲酯盐酸盐的测定提供了新方法。     

Sapindaceae,cyanolipids, and bugs

Scentless plant bugs (Heteroptera: Rhopalidae) are so named because adults of the Serinethinae have vestigial metathoracic scent glands. Serinethines are seed predators of Sapindales, especially Sapindaceae that produce toxic cyanolipids. In two serinethine species whose ranges extend into the southern United States,Jadera haematoloma andJ. sanguinolenta, sequestration of host cyanolipids as glucosides renders these gregarious, aposematic insects unpalatable to a variety of predators. The blood glucoside profile and cyanogenesis ofJadera varies depending on the cyanolipid chemistry of hosts, and adults and larvae fed golden rain tree seeds (Koelreuteria paniculata) excrete the volatile lactone, 4-methyl-2(5H)-furanone, to which they are attracted.Jadera fed balloon vine seeds (Cardiospermum spp.) do not excrete the attractive lactone. Loss of the usual heteropteran defensive glands in serinethines may have coevolved with host specificity on toxic plants, and the orientation ofJadera to a volatile excretory product could be an adaptive response to save time.Mention of a commercial product does not consititute an endorsement by the USDA.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

2008～2009年世界塑料工业进展

收集了2008年7月～2009年6月世界塑料工业的相关资料,介绍了2008～2009年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况。按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、环氧树脂、不饱和聚酯树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍。     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.