Enantioselective Henry reaction catalyzed by C2-symmetric chiral diamine–copper(II) complex
作者:Sermadurai Selvakumar、Dhanasekaran Sivasankaran、Vinod K. Singh
DOI:10.1039/b904254g
日期:——
A copper(II) complex of C2-symmetric diamine has been proved to be an efficient catalyst for the enantioselective Henry reaction between nitroalkanes and various aldehydes to provide β-hydroxy nitroalkanes in high yields (up to 97%), moderate diastereoselectivities (up to 71:29) and excellent enantiomeric excesses (up to 96%). The chiral nitroaldol adduct obtained has been further converted into chiral
The quadratic matrix equation AX2+ BX + C = 0in n × nmatrices arises in applications and is of intrinsic interest as one of the simplest nonlinear matrix equations. We give a complete characterization of solutions in terms of the generalized Schur decomposition and describe and compare various numerical solution techniques. In particular, we give a thorough treatment of functional iteration methods based on Bernoulli’s method. Other methods considered include Newton’s method with exact line searches, symbolic solution and continued fractions. We show that functional iteration applied to the quadratic matrix equation can provide an efficient way to solve the associated quadratic eigenvalue problem (λ2A + λB + C)x = 0.
二次矩阵方程 \( AX^2 + BX + C = 0 \) 在 \( n \times n \) 矩阵中出现于应用中,并且作为最简单的非线性矩阵方程之一,具有内在的重要性。我们给出了基于广义施尔分解的解的完整特征,并描述和比较了各种数值解法。特别地,我们对基于伯努利方法的函数迭代法进行了深入的探讨。考虑的其他方法包括具有精确线性搜索的牛顿法、符号解法和连分数法。我们表明,应用于二次矩阵方程的函数迭代法可以有效地解决相关的二次特征值问题 \( (\lambda^2 A + \lambda B + C)x = 0 \)。
Novel Bicyclic Piperazine Derivatives of Triazolotriazine and Triazolopyrimidines as Highly Potent and Selective Adenosine A<sub>2</sub><sub>A</sub> Receptor Antagonists
作者:Hairuo Peng、Gnanasambandam Kumaravel、Gang Yao、Li Sha、Joy Wang、Herman Van Vlijmen、Tonika Bohnert、Carol Huang、Chi B. Vu、Carol L. Ensinger、Hexi Chang、Thomas M. Engber、Eric T. Whalley、Russell C. Petter
DOI:10.1021/jm0494321
日期:2004.12.1
A series of bicyclic piperazine derivatives of triazolotriazine and triazolopyrimidines was synthesized. Some of these analogues show high affinity and excellent selectivity for adenosine A(2a) receptor versus the adenosine A(1) receptor. Structure-activity-relationship (SAR) studies based on octahydropyrrolo[1,2-a]pyrazine and octahydropyrido[1,2-a]pyrazine with various capping groups are reported. Among these analogues, the most potent and selective A(2a) antagonist 26h has a K-i value of 0.2 nM and is 16500-fold selective with respect to the A(1) receptor. Among a number of compounds tested, compounds 21a and 21c exhibited significantly improved metabolic stability. Compounds 21a, 21c, and 18a showed good oral efficacy in rodent catalepsy models of Parkinson's disease.