Sun Baoguo

Identification of volatile components in Chinese Sinkiang fermented camel milk using SAFE, SDE, and HS-SPME-GC/MS.

The volatile components of Chinese Sinkiang fermented camel milk were isolated by solvent assisted flavour evaporation (SAFE), simultaneous distillation extraction (SDE, dichloromethane and diethyl ether as solvent, respectively) and headspace solid-phase microextraction (HS-SPME, CAR/PDMS, PDMS/DVB and DVB/CAR/PDMS fibre extraction, respectively) and analysed by GC/MS. A total of 133 volatile components were identified under 6 different conditions, including 30 esters, 20 acids, 18 saturated alcohols, 15 unsaturated aliphatic alcohols, 8 saturated ketones, 9 saturated aldehydes, 8 unsaturated aliphatic aldehydes, 6 furans, 5 sulphur-containing compounds, 5 ethers, 5 lactones, 3 other compounds, and 1 unsaturated aliphatic ketone. Three pretreatment methods were compared, assisted by principal component analysis (PCA). The results indicated that the volatile components obtained using different methods varied greatly both in categories and in content, and therefore, a multi-pretreatment method should be adopted together with GC/MS. A total of 71 aroma-active compounds were detected by gas chromatography-olfactometry (GC-O), among which 66 aroma-active compounds were found by SDE (60, dichloromethane as solvent; 24, diethyl ether as solvent), 26 by SAFE.

Enantioselective synthesis of 2-hydroxy-5-methyl-3-hexanone

2-Hydroxy-5-methyl-3-hexanone was synthesised enantioselectively by Sharpless asymmetric dihydroxylation (Sharpless AD) or Shis asymmetric epoxidation (Shis AE) of 5-methyl-3-trimethylsiloxy-2-hexene. This was obtained in an E/Z ratio of 7.5/1 by deprotonation of 5-methyl-3-hexanone with NaHMDS in n-hexane followed by reaction with chlorotrimethylsilane. Optically active 2-hydroxy-5-methyl-3-hexanone was obtained in a 76.9% yield with a 75.6% ee when AD-mix-β was used as oxidant. Its absolute configuration was tentatively assigned to be R according to the AD face selection rule. AD-mix-α gave the product in a 69.2% yield only with a 15.7% ee. The major product had the same configuration as that obtained by AD-mix-β. Optically active 2-hydroxy-5-methyl-3-hexanone was obtained in a 54% yield with a 74.6% ee by Shis AE when a catalyst derived from D-fructose was used, while in a 50% yield with a 72.8% ee when a catalyst derived from L-fructose was used. The absolute configuration of the product obtained by a catalyst from D-fructose was deduced to be R whilst a catalyst from L-fructose gave the (S)-enantiomer by comparison of the retention time on a chiral column G-TA with the product obtained by AD-mix-β.

静态顶空-GC/MS技术分析浸膏中的溶剂残留

为研究浸膏类添加剂中的溶剂残留，采用静态顶空进样结合气质联用仪对5种浸膏（枸杞浸膏、山楂浸膏、杭白菊浸膏、茉莉浸膏、桂花浸膏）共15个样品中的27种残留溶剂进行了定性定量分析。静态顶空条件为60℃平衡15 min，进样体积为0.40 mL，利用NIST谱库和标准品定性，外标法定量。结果表明：①该方法对12种溶剂定量的线性范围良好，线性相关系数均大于0.99，回收率在78.60%～120.80%之间，相对标准偏差为11.50%～16.94%。②枸杞浸膏、山楂浸膏、杭白菊浸膏和桂花浸膏（GH1）中的主要残留溶剂为乙醇；桂花浸膏（GH2、GH3）和茉莉浸膏中的主要残留溶剂为甲基环戊烷、正己烷、异己烷和环己烷。

Epoxidation of β-pinene to 2,10-epoxypinane by Oxone

This paper describes a highly effective catalytic method for epoxidation of β-pinene to 2,10-epoxypinane using potassium peroxomonosulfate (Oxone) as oxidant and acetone as catalyst. Structure of 2,10-epoxypinane was characterized by data of infrared spectrum, GC-MS spectrum and 1H NMR spectrum. The procedure consists simply in stirring the substrate, NaHCO3 and acetone, at 0°C, with dropwise addition of an aqueous solution of Oxone. Optimization of the conditions identified (1) the mole ratio of Oxone to β-pinene 0.8:1, (2) reaction temperature 40°C, (3) pH 7.0–7.5, and (4) reaction time 2.5h. The yield of 2,10-epoxypinane can reach 85.4% and the system exhibits good chemical selectivity and few byproducts.