Absolute Configurational Assignment of Acyclic Hydroxy Carboxylic Acids: A New Strategy in Exciton-Coupled Circular Dichroism
摘要:
A new strategy in exciton-coupled circular dichroism (ECCD) is described for the configurational assignment of alpha-hydroxy carboxylic acids. Using 9-anthryldiazomethane (4), carboxyl groups can be selectively derivatized with a chromophore suitable for exciton coupling. In combination with the 2-naphthoate chromophore linked to the alpha-hydroxy group, the absolute stereochemistry of alpha-hydroxy carboxylic acids can be easily deduced from a single CD measurement. The usefulness of the new method is demonstrated with a series of alpha-hydroxy acids with different side chains. The developed microscale method is also useful for chiral amino acids and natural products containing carboxyl groups or similar structural units.
Diazo Preparation via Dehydrogenation of Hydrazones with “Activated” DMSO
摘要:
We report that "activated" dimethyl sulfoxide efficiently dehydrogenates hydrazones to the respective diazo species at -78 degrees C. Under optimized conditions, triethylamine hydrochloride is removed quantitatively by vacuum filtration to provide solutions of diazo compounds. Stable diazo species can be isolated in high yield, or alternatively, the direct treatment of these solutions with carboxylic acids provides esters.
The lipase-catalyzed acetylation of a broad spectrum of racemic 2-hydroxy acids 1 to their 2-acetoxy acids 2 was shown to proceed with high enantioselectivity. Thus, the microbial lipases, in particular from Candidaantarctica and Burkholderiaspecies, are convenient biocatalysts for the synthesis of optically active 2-hydroxy acids in excellent enantioselectivity (ee values up to > 99%). The absolute
A new exciton-coupled circular dichroism method for assigning the absolute configuration in acyclic α- and β-hydroxy carboxylic acids
作者:Olaf Gimple、Peter Schreier、Hans-Ulrich Humpf
DOI:10.1016/s0957-4166(96)00490-9
日期:1997.1
new exciton-coupled circular dichroism (ECCD) method is described for the configurational assignment of α- and β-hydroxy carboxylic acids. Using the chromophoric combination 2-naphthoate/9-methylanthryl group, the absolute stereochemistry of α- and β-hydroxy carboxylic acids can be deduced easily from a single CD measurement. The developed microscale method is also useful for chiral amino acids and natural
New Applications of the CD Exciton Chirality Method. Stereochemical Assignment of Organic Compounds Containing Carboxylic Acid Groups
作者:Anne Fischbeck、Nana Bartke、Hans-Ulrich Humpf
DOI:10.1007/s00706-004-0277-4
日期:2005.3
CDexcitonchiralitymethods are described for the stereochemical assignment of organic compounds containing carboxylic acid groups. Using the chromophoric combination 2-naphthoate or 2-anthroate and 9-anthrylmethyl group the absolute stereochemistry of α- and β-hydroxy carboxylic acids can be deduced from a single CD measurement. Furthermore, as demonstrated with cyclic and acylic dicarboxylic acids
A High-Yielding and Convenient Synthesis of Rotaxane Based On an Ester Forming Capping Methodology
作者:Yuji Tokunaga、Suzuka Kakuchi、Koichiro Akasaka、Naoki Nishikawa、Youji Shimomura、Kimio Isa、Toshihiro Seo
DOI:10.1246/cl.2002.810
日期:2002.8
An efficient method for preparation of rotaxanes, involving hydrogen bonding guided self-assembly and diaryldiazoalkanes ester forming end-capping of pseudorotaxanes, is described. The end-capping reactions proceed under mild conditions and furnish the expected rotaxanes in excellent yields.
tridecanoic acid from myristic acid reached 17%. An 18O-labeled oxidant study suggested that CYP152N1 catalysed the overoxidation of α-hydroxymyristic acid to form α-ketomyristic acid, which in turn was spontaneously decomposed by H2O2 to yield tridecanoic acid. Crystal structure analysis of CYP152N1 revealed its high similarity to other CYP152 family enzymes, such as CYP152A1 and CYP152B1. MD simulations of
属于CYP152家族的细胞色素P450过氧化酶使用H 2 O 2催化脂肪酸的氧化。CYP152N1从隔离微小杆菌属菌。AT1b在生理H 2 O 2浓度下专门催化肉豆蔻酸的α-选择性羟基化。但是,通过增加H 2 O 2(1-10 mM)的浓度,由肉豆蔻酸产生了一系列短链烷基脂肪酸,例如十三烷酸。由肉豆蔻酸得到的十三烷酸的收率达到17%。一个18O标记的氧化剂研究表明CYP152N1催化α-羟基肉豆蔻酸的过氧化反应形成α-酮麦芽酸,然后H 2 O 2自发分解生成十三烷酸。CYP152N1的晶体结构分析显示,它与其他CYP152家族酶(例如CYP152A1和CYP152B1)具有高度相似性。CYP152N1中容纳的α-羟基肉豆蔻酸的MD模拟提出了α-羟基肉豆蔻酸可能用于脱羧反应的预氧化构象。