N-(Chloroacetyl)- and N-(dichloroacetyl)-N-(xylyl)alanine esters: assignment of the absolute configurations and enantiodifferentiation by the dirhodium method
作者:Edison Díaz Gómez、Jorge Jios、Carlos O. Della Védova、Hugo D. March、Héctor E. Di Loreto、Gábor Tóth、Andras Simon、Dieter Albert、Stefan Moeller、Rudolf Wartchow、Helmut Duddeck
DOI:10.1016/j.tetasy.2005.06.008
日期:2005.7
derivatives) containing either stereogenic centres alone as in 1 and 3 or stereogenic centres plus chiral axes as in 2 and 4 were investigated. The latter have been examined in terms of the absolute configurations of the diastereomers in unresolvable mixtures, which were determined by evaluating NOE contacts in preferred conformations. Although these ligands are weak donors in Rh* adducts, it is easily
四氯化Ñ -acylalanine甲酯(甲霜灵®含有任一立体中心单独作为衍生物)1个3或立体中心加手性轴在2和4进行了研究。已根据不可拆分混合物中非对映异构体的绝对构型检查了后者,这是通过评估优选构型的NOE接触来确定的。尽管这些配体是Rh *加合物中较弱的供体,但很容易通过“ dir法”监测其对映体纯度。令人惊讶的是,只有一氯衍生物1和2在标准dirhodium方法条件下(包括一滴丙酮-d 6以增强Rh *的溶解度)在手性识别实验中获得令人满意的结果。二氯衍生物3和4失效。然而,他们在没有丙酮-d 6的情况下产生了显着的分散效果。结果表明,一氯衍生物1和2中优选的络合位点主要是酰胺羰基氧,而在二氯衍生物3和4的情况下该基团几乎不可用,因此酯基似乎是络合位点。