Efficient and practical synthesis of (R)-2-methylpyrrolidine

An efficient, practical, and high yielding synthesis of (R)-2-methylpyrrolidine is described. The sequence allows for the scalable preparation of the target compound in just four synthetic steps and proceeds in 83% overall yield and >99% optical purity from readily available starting materials.     

Stereoselective preparation of a cyclopentane-based NK1 receptor antagonist bearing an unsymmetrically substituted sec-sec ether

A highly efficient synthesis of the potent and selective NK-1 receptor antagonist 1 is described. The key transformation involved the etherification reaction between cyclopentanol 12 and chiral imidate 30 which was catalyzed by HBF4 to initially give ether 14 as a 17:1 mixture of diastereomers and in 75% combined yield. The diastereoselectivity was upgraded to 109:1 by crystallization of the triethylamine solvate 44 which was isolated in 54% yield from 12. Mechanistic studies confirmed that the etherification reaction proceeds through an unprecedented S(N)2 reaction pathway under typical S(N)1 reaction conditions.     

一维热传导方程热源反问题基于最小二乘法的正则化方法

研究一维热传导方程热源反问题.给出基于最小二乘支持向量机（LS-SVM）求解的半解析表达式,此外还给出一种参数调节方法以及算法稳定性的证明.数值实验表明该方法具有较高的数值精度和稳定性.     

Asymmetric total synthesis of (+)-cannabisativine

The asymmetric total synthesis of natural (+)-cannabisativine 1 was completed in 19 steps and 7% overall yield. The key synthetic intermediate 29 was prepared with a high degree of stereocontrol in 12 steps starting from chiral 1-acylpyridinium salt 10. Addition of zinc enolate 11 to pyridinium salt 10 furnished dihydropyridone 12 containing two contiguous stereocenters of the correct absolute configuration. Luche reduction of ketone 16 afforded diol 17 in high yield (96%) and excellent diastereoselectivity. The Mukaiyama-Michael reaction of pyridones 27a/b with O-silyl ketene acetal 32 gave phenyl selenyl ketones 33a/b with complete stereoselectivity. Elimination of cis-beta-hydroxyselenides 34 and 35 effected the regiocontrolled preparation of tetrahydropyridine derivative 29. Several approaches to the macrocyclic ring closure of the 13-membered ring were investigated, ultimately leading to the completion of an asymmetric synthesis of the target compound with a high degree of stereocontrol.     

Transforming NMR data despite missing points.

Some NMR experiments produce data with several of the initial points missing. The inverse discrete Fourier transform (IDFT) assumes these points are present so the data cannot be so transformed without artifact-ridden results. This problem is often particularly severe when projection imaging with free-induction decays (FIDs). This paper compares recent methods for obtaining a projection from incomplete data and elaborates on their strengths and limitations. One method is to write the transform that would take the desired projection to the truncated data set, and then solve the matrix equation by singular value decomposition. A second replaces the missing data with zeros, so that an IDFT produces a projection with unwanted artifacts. Then one solves the matrix equation that takes the desired projection to the artifact-ridden projection. A third uses the same artifact-ridden projection, but fits the region outside the bandwidth of the sample with as many sinusoidal functions as there are missing data. The coefficients of these functions are estimates of the missing data, and the projection is obtained by transforming the completed FID or subtracting the extrapolation of the fitted curve from the region containing the object. We show that when all three methods are applicable, they theoretically produce the same result. They differ by ease of implementation and possibly by computational errors. They give a result similar to that of the previous method that iteratively corrects the FID and projection after repeated IDFTs and DFTs. We find that one can obtain a projection despite missing a substantial number of data.     

高剥离态Fe Ⅹ Ⅵ离子能级寿命测量

在原子能院串列加速器上,利用束箔方法,测量了能量为30 MeV Fe离子产生的高剥离态谱线跃迁结构的寿命值.在30 MeV时,Fe通过箔膜的电荷态分布在7+到17+,我们选择Fe XⅥ2p~6(~1S)4p—2p~6(~1S)5d(~2P_(3/2)~o—~2D_(3/2))的谱线,谱线波长124.696(?),能级寿命为79±4 ps.最后对实验误差进行了分析.     

Asymmetric Diels-Alder reactions of chiral cyclopropylidene imide dienophiles: preparation of gem-dimethyl- and spirocyclopropane norbornyl carboxylic acids

A highly efficient strategy has been developed for the rapid asymmetric synthesis of gem-dimethyl and spirocyclopropyl norbornyl carboxylic acids. The key transformation involved the unprecedented asymmetric Diels-Alder reaction of highly reactive beta,beta-cyclopropyl-alpha,beta-unstaturated N-acyloxazolidinones with cyclopentadiene affording the adducts in high yield and de.     

甲烷在石墨化热解碳黑和活性炭上的吸附

为研究影响碳基吸附剂吸附超临界温度气体的主要因素,选择石墨化热解碳黑BP280和Ajax活性炭,分析超临界温度高压甲烷在其上的吸附平衡。应用容积法,在压力0~20.5 MPa、温度253 K~313 K测定甲烷的吸附平衡数据,并由等量吸附线标绘和亨利定律常数确定等量吸附热。引入通用吸附等温方程,再由方程的Langmuir标绘确定最大吸附容量,进而通过方程的线性化计算吸附平衡态中甲烷分子的作用能。结果表明,甲烷在两种吸附剂上的最大吸附容量均随温度而变化,并都小于液态甲烷的密度;甲烷在碳黑和活性炭上的等量吸附热分别为11.9 kJ/mol~12.5 kJ/mol和17.5 kJ/mol~22.5 kJ/mol,体现了两种吸附剂不同的表面能量分布;甲烷分子间作用能随吸附量的变化特点反映了超临界温度甲烷以类似于压缩气体状态聚集的特点和吸附剂结构上的差异。碳基吸附剂的比表面积和微孔容积是影响其储存甲烷容量的重要因素。     

Addition of indolyl and pyrrolyl grignard reagents to 1-acylpyridinium salts

Certain indolyl and pyrrolyl Grignard reagents add to 1-acyl salts of 4-methoxy-3-(triisopropylsilyl)pyridine to give the corresponding 1-acyl-2-heteroaryl-2,3-dihydro-4-pyridones in good to high yield. When the 1-acyl group contained a chiral auxiliary, (+/-)-trans-2-(alpha-cumyl)cyclohexyloxy, addition of the indolyl Grignards resulted in a separable mixture of diastereomeric 2,3-dihydro-4-pyridones.