Environmental behavior of the chiral acetamide pesticide metalaxyl: enantioselective degradation and chiral stability in soil

Racemic metalaxyl is currently being replaced in many countries by metalaxyl-M, the fungicide enantiomerically enriched with the biologically active R-enantiomer. This "chiral switch" is expected to reduce the amount of pesticide released into the environment as well as potential side-effects on nontarget organisms. Detailed knowledge of the environmental behavior of such chiral compounds should include information on the chiral stability (interconversion of enantiomers). In the present study, the degradation/ dissipation of metalaxyl and its primary carboxylic acid metabolite (MX-acid) in soil was investigated under laboratory conditions using enantioselective gas chromatography mass spectrometry (GC-MS). Racemic and the enantiopure R- and S-compounds were incubated in separate experiments. The degradation of metalaxyl was shown to be enantioselective with the fungicidally active R-enantiomer being faster degraded than the inactive S-enantiomer, resulting in residues enriched with S-metalaxyl when the racemic compound was incubated. The relatively high enantioselectivity suggests that degradation/dissipation was largely biological. The data indicated a conversion of 40-50% of metalaxyl to MX-acid, and the remaining metalaxyl being degraded via other pathways. The degradation of MX-acid was also enantioselective. Metalaxyl and MX-acid were both configurationally stable in soil, showing no interconversion of R- to S-enantiomers, and vice-versa. Furthermore, the conversion of metalaxyl to MX-acid proceeded with retention of configuration. Degradation followed approximate first-order kinetics but showed significant lag phases.     

Environmental behavior of the chiral triazole fungicide fenbuconazole and its chiral metabolites: enantioselective transformation and degradation in soils

Fenbuconazole is a widely used systemic agricultural fungicide of the triazole class with one chiral center. In the present study, the enantioselective degradation of fenbuconazole and its chiral metabolites, RH-9129 and RH-9130, in two soils under aerobic and anaerobic conditions were investigated using a chiral OD-RH column on a reversed-phase liquid chromatography-tandem mass spectrometry system. Under aerobic or anaerobic conditions, the results showed the occurrence of enantioselectivity with (-)-fenbuconazole preferentially degraded in both soils. Further enantioselective analysis of converted products showed that the concentrations of four RH-9129 and RH-9130 stereoisomers were different from each other under both aerobic and anaerobic conditions. The four stereoisomer concentrations followed the order (-)-RH-9129 > (+)-RH-9129 > (-)-RH-9130 > (+)-RH-9130 in Langfang alkaline soil. However, in the case of Changsha acidic soil, different RH-9129 and RH-9130 stereoisomer patterns were produced in the order (-)-RH-9129 > (+)-RH-9129 > (+)-RH-9130 > (-)-RH-9130. The (-)-RH-9129 stereoisomer had the highest concentration formed by transformation of fenbuconazole in both soils. The degradation of RH-9129 and RH-9130 in the two soils is also stereoselective under both aerobic and anaerobic conditions, the results indicating that the (+)-RH-9130 enantiomer degraded faster than the (-)-RH-9130 enantiomer and the (+)-RH-9129 enantiomer degraded faster than the (-)-RH-9129 enantiomer. In addition, the (-)-RH-9129 isomer exhibited the slowest degradation rate in both soils. This study provides the first experimental evidence of stereoselective degradation and transformation of fenbuconazole as well as its chiral metabolites in the environment.     

Concentrations and chiral signatures of polychlorinated biphenyls in outdoor and indoor air and soil in a major U.K. conurbation

Concentrations and chiral signatures of polychlorinated biphenyls (PCBs) were measured in outdoor air (using polyurethane foam (PUF)--disk passive samplers) and surface soil samples taken at approximately monthly intervals over 1 year at 10 locations on a rural-urban transect across the West Midlands of the U.K. In both air and soil, concentrations clearly decrease with increasing distance from the city center, supporting the existence of an urban "pulse", that indicate the West Midlands conurbation to be a source of PCBs to the wider environment. Concentrations of PCBs in outdoor air samples in this study are well below those reported previously for indoor air in the West Midlands. This, combined with comparison of chiral signatures in outdoor air and soil with those in samples of indoor air taken in the West Midlands, suggest strongly that the principal contemporary source of PCBs in this conurbation is ventilation of indoor air and not volatilization from soil. Future reductions in PCB concentrations in outdoor air and ultimately human exposure appear best achieved by action to remove remaining sources of PCBs from existing structures.     

生物催化法制备手性酮基布洛芬的研究进展

酮基布洛芬是一种重要的消炎镇痛药,广泛应用于风湿、类风湿性关节炎、脊髓炎和痛风等疾病的治疗,成为处方量最大的药物之一.市售的酮基布洛芬以外消旋体为主,(S)-酮基布洛芬为其活性对映体,(R)-酮基布洛芬的存在会加重肝脏的代谢负担.目前手性酮基布洛芬主要通过化学合成法生产,与传统的化学法相比,生物催化法具有反应条件温和、对环境友好等优点,成为近年来研究的热点.生物催化法主要利用脂肪酶、酯酶和腈水合酶/酰胺酶双酶体系等催化制备手性酮基布洛芬.同时对生物催化法制备手性酮基布洛芬的研究进展进行了综述.     

Enantiomeric profiling of chiral drugs in wastewater and receiving waters

The aim of this paper is to discuss the enantiomer-specific fate of chiral drugs during wastewater treatment and in receiving waters. Several chiral drugs were studied: amphetamine-like drugs of abuse (amphetamine, methamphetamine, MDMA, MDA), ephedrines (ephedrine and pseudoephedrine), antidepressant venlafaxine, and beta-blocker atenolol. A monitoring program was undertaken in 7 WWTPs (utilizing mainly activated sludge and trickling filters technologies) and at 6 sampling points in receiving waters over the period of 9 months. The results revealed the enantiomer-specific fate of all studied drugs during both wastewater treatment and in the aqueous environment. The extent of stereoselectivity depended on several parameters including: type of chiral drug (high stereoselectivity was recorded for atenolol and MDMA), treatment technology used (activated sludge showed higher stereoselectivity than trickling filters), and season (higher stereoselectivity was observed in the aqueous environment over the spring/summer time).     

Volatilization of weathered chiral and achiral chlordane residues from soil

To mitigate the impact on the environment of persistent organic pollutants (POPs), we must understand thoroughly their environmental fate. Residues of many of these pollutants are still present in soil years after their legitimate uses were banned. In this report, the volatilization of one such persistent pollutant, chlordane, from a field where it was applied approximately 40 years ago, is examined in detail overthe course of several years. Ambient air samples were collected at three heights above the treated soil throughout the investigation. Air samples were also collected at several background sites in Connecticut for comparison. Analysis of these samples shows that chlordane volatilization from soil continues to occur long after initial application, at rates dependent on both temperature and cultivation of the soil. Comparison of relative concentrations and enantiomeric profiles for components of technical chlordane in atmospheric samples from a variety of sources suggests a regional, urban input of chlordane to the ambient air over Connecticut, possibly related to the widespread termiticidal use of chlordane in home foundation soils.     

The chiral principles contained in structure-sweetness relations

Two chiral principles have been developed. When applied concertedly, they lead to a third principle. The latter affords a solution to the chiral anomaly presented by the fact that, whilst the sweet receptor site is chiral, and the $\text{d}\text{-}\text{amino acids}$ are correspondingly sweet and the $\text{l}\text{-}\text{amino acids}$ are not, both enantiomeric forms of the sugars taste sweet.     

手性含氮饱和杂环醇的化学法与生物酶法合成

手性含氮饱和杂环醇是一类重要的有机化合物,是许多合成药物和天然活性物质的结构组成单元。综述了哌啶醇、奎宁醇及吡咯烷醇等手性醇的化学及生物酶法合成进展,重点介绍了生物酶法在制备手性哌啶醇、奎宁醇及吡咯烷醇中的应用。     

手性三唑类农药分离分析及立体选择性行为研究进展

手性三唑类杀菌剂一般含有1或2个手性中心,存在2～4个对映体,是目前用于病虫害防治使用最广泛的杀菌剂。现有大量实验表明,手性三唑类杀菌剂对映体具有选择性降解行为,且对映体毒性活性存在差异,为更准确地评估手性农药的风险,亟需针对手性单体进行研究,但手性农药对映体间因有相同的理化性质,难以用常规手段进行分离分析。因此,手性分离检测方法一直是领域研究的重点和热点,朝着快速、高效、精准的领域发展。本文通过对手性三唑类农药分离分析及立体选择性行为研究进展进行综述,旨在明确手性农药在环境及植株体内的立体选择性行为,为手性农药高效低风险的使用提供数据支撑。     

手性香料3-巯基己醇及其乙酸酯的不对称合成

研究了以(E)-2-已烯醛为起始原料,通过还原、Sharpless不对称环氧化、区域选择性还原、S_N2亲核取代等反应制备光学活性的3-巯基己醇和3-巯基己基乙酸酯的方法.(E)-2-己烯醛通过NaBH_4还原得到(E)-2-己烯醇,产率91%左右.(E)-2-己烯醇通过Sharpless不对称环氧化,得到光学活性2,3-环氧己醇,化学产率86%左右,产物e.e.值94%左右.2,3-环氧己醇用Red-Al进行区域选择性还原得到光学活性的1,3-己二醇,产率82%左右.1.3-已二醇的伯羟基转化为乙酸酯,3位羟基转化为甲磺酸酯,然后通过S_N2亲核取代反应,得到3-乙酰硫基己基乙酸酯,三步反应总产率61%左右.3-乙酰硫基己基乙酸酯在氢氧化钠的作用下将乙酰硫基水解,得到3-巯基己基乙酸酯,产率85%左右;3-乙酰硫基己基乙酸酯在过量氢氧化钠的作用下完全水解,得到3-巯基己醇,产率82%左右.最终产物3-巯基己醇和3-巯基己基乙酸酯e.e.值均在94.0%左右. 值94%左右.2,3-环氧己醇用Red-Al进行区域选择性还原得到光学活性的1,3-己二醇,产率82%左右.1.3-已二醇的伯羟基转化为乙 酯,3位羟基转化为甲磺酸酯,然后通过S_N2亲核取代反应,得到3-乙酰硫基己基乙酸酯,三步反应总产率61%左右.3-乙酰硫基己基乙酸酯在氢氧化钠的作用下将乙酰硫基水解,得到3-巯基己基乙酸酯,产率85%左右;3-乙酰硫基己基乙酸酯在过量氢氧化钠的作用下完全水解,得到3-巯基己醇,产率82%左右.最终产物3-巯基己醇和3-巯基己基乙酸酯e.e.值均在94.0%左右. 值94%左右.2,3-环氧己醇用Red-Al进行区域 择性还原得到光学活性的1,3-己二醇,产率82%左右.1.3-已二醇的伯羟基转化为乙 酯 3位羟基转化为甲磺酸酯,然后通过S_N2亲核取代反应,得到3-乙酰硫基己基乙酸酯,三步反应总产率61%左右.3-乙酰硫基己基乙酸酯在氢氧化钠的作用下将乙酰硫基水解,得到3-巯基己基乙酸酯,产率85%左右;3-乙酰硫基己基乙酸酯在过量氢氧化钠的作用下完全水解,得到3-巯基己醇,产率82%左右.最终产物3-巯基己醇和3-巯基己基乙酸酯e.e.值均在94.0%左右. 值94%左右.2,3-环氧己醇用Red-Al进行区域 择性还原得到光学活性的1,3-己二醇,产率82%左右.1.3-已二醇的伯羟基转化为乙 酯 3位羟基转化为甲磺酸酯,然后通过S_N2亲核取代反应,得到3-乙酰硫基己基乙酸酯,三步反应总产率61%左右.3-乙酰硫基己基乙酸酯在氢氧化钠的作用下将乙酰硫基水解,得到3-巯基己基乙酸酯,产率85%左右;3-乙酰硫基己基乙酸酯在过量氢氧化钠的作用下完全水解,得到3-巯基己醇,产率82%左右.最终产物3-巯基己醇和3-巯基己基乙酸酯e     

Biocatalytic production of chiral epichlorohydrin in organic solvents

Enantioselective hydrolysis of racemic epichlorohydrin was accomplished for the production of enantiopure epichlorohydrin using the whole cells of an isolated Aspergillus niger spps. To overcome the spontaneous chemical degradation of epichlorohydrin that occurs in aqueous buffer, organic solvents were employed in the reaction medium. The enantioselectivity was highly dependent on the solvent structure, water content of the medium, and the initial epichlorohydrin concentration. (S)-epichlorohydrin could be obtained from its racemates (60 mM) with an optical purity of 100% enantiomeric excess (ee) and 20% yield in cyclohexane supplemented with 2.0% (v/v) water.     

脂肪酶促手性拆分中立体选择性的调控因素

脂肪酶催化手性拆分是制备光学活性化合物的重要手段.文章总结了酶法拆分技术近年来的发展,重点探讨了反应溶剂,底物结构,酶的预处理.添加助剂等对酶催化活性及立体选择性的影响规律;以及相关的手性拆分的调控策略.论述了合理利用或调整上述相关因素可有效提高酶促拆分选择性及催化效率.     

Emission of chiral organochlorine pesticides from agricultural soils in the cornbelt region of the U.S

Several organochlorine pesticides are chiral molecules manufactured as racemic mixtures. Past research has shown that selective degradation of pesticide enantiomers by microorganisms occurs resulting in nonracemic signatures in soils. In this work, volatilization of chiral pesticides from soil was investigated to determine if enantioselective breakdown in soils could be used as a source signature to track releases of chiral pesticides to the atmosphere. Air samples were taken directly above agricultural soils at several sites, and enantiomeric signatures were found to be nonracemic following patterns found in the soil. A follow up study at one site showed that for most compounds concentration decreased with increasing height above the soil, while enantiomer fractions for chiral pesticides were similar to that found in the soil, signifying the soil as a source to the air. The enantiomer fractions of ambient air samples from rural nonagricultural areas in the region were also found to be nonracemic.     

Enantioseparation of catechin and epicatechin in plant food by chiral capillary electrophoresis

The enantiomers of catechin and epicatechin were separated by chiral capillary electrophoresis using modified cyclodextrins as chiral selectors. Various conditions for the separation system were optimized, including the pH value and the concentration of the running buffer. A baseline separation of the catechin and epicatechin enantiomers could be achieved by using 0.1 mol l⁻¹ borate buffer (pH 8.5) with 12 mmol l⁻¹ (2-hydroxypropyl)-γ-cyclodextrin as chiral selector, a fused-silica capillary with 40 cm effective length (75 μm I.D.), +18 kV applied voltage, a temperature of 20 °C and direct UV detection at 280 nm. The method was applied to different plant food samples. (+)-Catechin and (−)-epicatechin could be verified as the most common flavan-3-ols. In the case of guaraná, however, we were able to identify all four enantiomers, both (+)- and (−)-catechin and (+)- and (−)-epicatechin, as naturally occurring compounds. This finding was verified by further isolation and purification of the flavan-3-ols and subsequent LC–MS analysis. This method allows for the identification of the authenticity of guaraná through the analysis of the catechin and epicatechin enantiomers, additionally to the conventional methods like HPLC.     

Effect of electrolyzed reduced water on chiral theanine and polyphenols in tea

Pure d/l-theanine enantiomers were synthesized separately, and SEM was used for their crystal-structure observation. The novel enantiomeric separating method by HPLC was established using the chiral selector of β-CD in the mobile phase. Green tea, white tea, oolong tea, black tea and Pu-erh tea were tested for theanine enantiomers by different degrees of fermentation. The significantly higher d-enantiomeric proportion of theanine was found in white tea than the others, which was probably due to its specific processing step of withering. The effect of electrolyzed reduced water (ERW) on enantiomeric theanine and polyphenols in tea was explored. There was no change of theanine, but rather a loss of ECG (epicatechin gallate) and an increasing amount of GA (gallic acid). ERW also reduced tea cream, which contains significant amount of polyphenols, indicating its potential application in the tea-beverage industry.     

消旋氧氟沙星抗体制备及其手性识别特性研究

采用活泼酯法（A）和直接EDC（1-乙基-3-（3-二甲氨丙基）碳二亚胺盐酸盐）法（D）,合成两种包被抗原（OFL-A-OVA和OFL-D-OVA）和两种免疫抗原（OFL-A-BSA和OFL-D-BSA）,然后分别用两种免疫抗原免疫小鼠获得与其对应的多克隆抗体,建立消旋氧氟沙星残留免疫检测方法。研究结果表明：紫外扫描图谱证明四种抗原均合成成功,OFL-A-BSA、OFL-D-BSA、OFL-A-OVA和OFL-D-OVA的偶联比分别为19.67、3.03、1.93和0.99。消旋氧氟沙星的间接竞争ELISA法的线性检测范围为16.35～444.10ng/mL,IC50为5.42ng/mL,最低检测限为6.23ng/mL。消旋氧氟沙星抗体与恩诺沙星、环丙沙星、加替沙星等其他同类药物的交叉反应率较低,表明消旋氧氟沙星抗体具有较高的特异性,且消旋氧氟沙星抗体对左旋氧氟沙星和右旋氧氟沙星的识别并非对等,对左旋的识别能力较大,左旋氧氟沙星对抗体的产生起主要作用。     

白酒中特征手性物质的SLE-GC-MS识别方法

运用固相支撑-液液萃取(solid-supported liquid-liquid extraction,SLE)技术和手性环糊精气相色谱柱建立了白酒中乳酸乙酯的2种对映体和2,3-丁二醇的3种对映体的分析方法,采用内标标准曲线定量。结果表明,乳酸乙酯、2,3-丁二醇在各自质量浓度范围内线性关系良好,在基质样品中的平均加标回收率在80%以上,相对标准偏差为1.34%~8.50%。该方法测得D-、L-乳酸乙酯和S-、R-、meso-2,3-丁二醇的检出限分别是64.32、47.74、62.70、59.08和26.58μg/L。利用所建立方法对酱香、浓香、清香3种香型的6种市售白酒样品进行分析,目标手性对映体在所选6个酒样中含量及比例不同,并首次在白酒中分离出S-2,3-丁二醇。该方法具有高效灵敏、精密度和准确度高、易操作等特点,适用于白酒中手性物质的检测,可为利用手性识别进行白酒质量监控、原产地溯源、品质鉴定提供新思路。