Stephens Philip J, Pan Jian-Jung, Devlin Frank J, Urbanová Marie, Hájícek Josef
Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA.
J Org Chem. 2007 Mar 30;72(7):2508-24. doi: 10.1021/jo062567p. Epub 2007 Mar 6.
The development of density functional theory (DFT) methods for the calculation of vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and transparent spectral region optical rotation (OR) has revolutionized the determination of the absolute configurations (ACs) of chiral molecules using these chiroptical properties. We report the first concerted application of DFT calculations of VCD, ECD, and OR to the determination of the AC of a natural product whose AC was previously undetermined. The natural product is the alkaloid schizozygine, isolated from Schizozygia caffaeoides. Comparison of DFT calculations of the VCD, ECD, and OR of schizozygine to experimental data leads, for each chiroptical technique, to the AC 2R,7S,20S,21S for the naturally occurring (+)-schizozygine. Three other alkaloids, schizogaline, schizogamine, and 6,7-dehydro-19beta-hydroxyschizozygine, have also been isolated from S. caffaeoides and shown to have structures closely related to schizozygine. Assuming a common biosynthetic pathway, their ACs are defined by that of schizozygine.
用于计算振动圆二色性（VCD）、电子圆二色性（ECD）和透明光谱区域旋光性（OR）的密度泛函理论（DFT）方法的发展，彻底改变了利用这些手性光学性质来确定手性分子绝对构型（AC）的方式。我们报道了首次将VCD、ECD和OR的DFT计算协同应用于一种天然产物绝对构型的测定，该天然产物的绝对构型此前尚未确定。该天然产物是从咖啡裂果茶（Schizozygia caffaeoides）中分离得到的生物碱裂果碱。将裂果碱的VCD、ECD和OR的DFT计算结果与实验数据进行比较，对于每种手性光学技术而言，天然存在的（+）-裂果碱的绝对构型均为2R,7S,20S,21S。另外三种生物碱，裂果加林、裂果胺和6,7-脱氢-19β-羟基裂果碱，也已从咖啡裂果茶中分离出来，并显示出与裂果碱结构密切相关。假设存在共同的生物合成途径，它们的绝对构型由裂果碱的绝对构型确定。
