Palladium‐Catalyzed Highly Chemo‐, Regio‐ and Stereoselective Synthesis of Eight‐ to Ten‐Membered Lactones from Allenyl 3‐Oxoalkanoates and Organic Halides

A highly chemo‐, regio‐, and stereoselective synthesis of eight‐ to ten‐membered lactones via the coupling cyclization of readily available allenyl 3‐oxoalkanoates and organic halides through an anti‐π‐allylic palladium intermediate is reported. The yields ranged from moderate to good.     

QuEChERS-超高效液相色谱-串联质谱法快速测定饮料中13 种饱和内酯类合成香料

建立超高效液相色谱-串联质谱法快速测定饮料中13 种饱和内酯类合成香料的方法。采用QuEChERS前处理法,以乙腈提取,N-丙基乙二胺填料吸附剂直接净化,电喷雾离子源、多反应监测正离子模式扫描,外标法定量。13 种饱和内酯在0.025～0.50 μg/mL范围内质量浓度与峰面积呈良好的线性关系,仪器检出限为0.025 μg/mL,方法的检出限为0.10 mg/kg,定量限为0.40 mg/kg,添加量为0.10、0.20、0.40 mg/kg时13 种饱和内酯的平均回收率范围分别为88.5%～103%,相对标准偏差为3.8%～11%（n=10）。本方法可用于饮料中饱和内酯类化合物的快速定性、定量检测。     

Volatile lactones from streptomycetes arise via the antimycin biosynthetic pathway

The volatiles released by several streptomycetes were collected by using a closed-loop stripping apparatus (CLSA) and analysed by GC-MS. The obtained headspace extracts of various species contained blastmycinone, a known degradation product of the fungicidal antibiotic, antimycin A(3b), and several unknown derivatives. The suggested structures of these compounds, based on their mass spectra and GC retention indices, were confirmed by comparison to synthetic reference samples. Additional compounds found in the headspace extracts were butenolides formed from the blastmycinones by elimination of the carboxylic acid moiety. Analysis of a gene knockout mutant in the antimycin biosynthetic gene cluster demonstrated that all blastmycinones and butenolides are formed via the antimycin biosynthetic pathway. The structural variation of the blastmycinones identified here is much larger than within the known antimycins, thus suggesting that several antimycin derivatives remain to be discovered.     

Tuning of Regioselectivity in Inorganic Iodide‐Catalyzed Alkylation of 2‐Methoxyfurans via Electronic and Steric Effects

In the presence of inorganic iodide, the methoxy C O bond in 2‐methoxyfurans may be cleaved to afford the corresponding lactonic anion. Due to the presence of an electron‐withdrawing group at the 3‐position, the alkylation with normal organic iodides occurred at the 3‐position highly regioselectively. However, when electron‐deficient allylic iodides with an electron‐withdrawing group at the 2‐position were used the 5‐alkylation products were formed as the major products with sodium iodide as the catalyst. With magnesium iodide as the catalyst, the 5‐allylation occurred highly regioselectively. As a whole, the 3‐ vs. 5‐alkylation selectivity may be determined by the relative steric hindrance at the 3‐ and 5‐positions and the electronic effect of the allylic iodides. A rationale was proposed.     

固相萃取结合气相色谱-质谱技术定量白酒中的γ-内酯

γ-内酯是食品中的一类重要风味化合物,存在于水果、葡萄酒及白酒等多种食品中。该研究通过液液萃取及固相萃取(SPE)方法,结合气相色谱-质谱(GC-MS),分别定性、定量了白酒中的8种γ-内酯。该定量方法快速,选择性强,对白酒中各内酯均有较好的线性(R2≥0.9908,γ-十二内酯),检出限范围为0.22(γ-癸内酯)～4.30μg/L(γ-壬内酯),低于各内酯的阈值,对不同香型成品酒及原酒的重现性均较好(RSD<15%),可用于白酒中微量成分γ-内酯的快速分析测定。     

Inhibition of biofilm formation of Pseudomonas aeruginosa by an acylated homoserine lactones-containing culture extract

The objective of this study was to examine the effect of an acylated homoserine lactones-containing culture extract (AHL-CCE) on bacterial growth, enzyme activity and biofilm formation of Pseudomonas aeruginosa. Chicken breast muscle broth in which P. aeruginosa had been grown for 24 h at 20 °C was extracted with acidified ethyl acetate, the solvent was evaporated and the residue was dissolved in water and heated at 100 °C for 15 min. Thin-layer chromatography combined with Agrobacterium tumefaciens KYC55-based bioassays indicated the presence of C₄-, C₆-, C₈- and C₁₂-homoserine lactones in the extract. The addition of AHL-CCE to a culture of P. aeruginosa caused the bacteria to reach their highest count after 36 h whereas cultures without the extract required 72 h to reach their peak counts, but the maximum cell count was higher for the extract-free culture. No biofilm was detected when P. aeruginosa was cultured in chicken broth at 10 °C when the extract was present. Addition of extract reduced proteolysis of actin, troponin-T and tropomyosin by P. aeruginosa, but had no effect on lipase activity. Therefore, AHL-CCE can be used to reduce the bacterial growth time and inhibit biofilm formation; thus, benefiting food safety and quality.     

银杏萜内酯的化学成分及药理作用

银杏萜内酯由银杏叶中提取，经萃取、吸附和重结晶制成纯品，用化学和光谱方法鉴定，它的主要成分是银杏内酯A、B、C、M、J和白果内酯．这些化学成分具有抑制血小板活化因子-PAF和对心肌缺血、脑缺血缺氧的保护作用．     

Aroma of Canned Peach Halves Acidified with Clarified Lemon Juice

The aroma composition of canned peaches was studied during the 1st year of storage. Citric acid was substituted with 2 types of lemon juice: turbid and clarified. The volatiles were extracted using a distillation technique and quantified by gas chromatography‐mass spectrometry. A total of 35 aroma compounds were identified and quantified, with the major volatile components being lactones. The removal of monoterpenes, during the tangential flow filtration of the lemon juice, provided an acidifier with high scores in the sensory evaluation. In this study, a product perceived by the consumers as more “natural” was elaborated, and new industrial perspectives were opened for the lemon industry and agriculture.     

N‐Methyl‐Substituted Fluorescent DAG–Indololactone Isomers Exhibit Dramatic Differences in Membrane Interactions and Biological Activity

N‐methyl‐substituted diacylglycerol–indololactones (DAG–indololactones) are newly synthesized effectors of protein kinase C (PKC) isoforms and exhibit substantial selectivity between RasGRP3 and PKCα. We present a comprehensive analysis of membrane interactions and biological activities of several DAG–indololactones. Translocation and binding activity assays underline significant variations between the PKC translocation characteristics affected by the ligands as compared to their binding activities. In parallel, the fluorescent properties of the ligands were employed for analysis of their membrane association profiles. Specifically, we found that a slight change in the linkage to the indole ring resulted in significant differences in membrane binding and association of the DAG–indololactones with lipid bilayers. Our analysis shows that seemingly small structural modifications of the hydrophobic regions of these biomimetic PKC effectors contribute to pronounced modulation of membrane interactions of the ligands.