Simplification of the induced circular dichroism method and its application to biologically active natural products

1)含有非手性苯乙基生色基团的手性酰胺的圆二色谱在240 nm附近观察到双标记的CD曲线。在对衍生物的构象分析中，观察到激子手性的标志与两个2-萘基的螺旋感觉(正/顺时针；负/逆时针)密切相关。半经验分子轨道计算(AM1)表明分子内存在氢键。N-甲基化后，反足酰胺类化合物的圆二色谱在225 nm处发生裂解。此外，N-甲基酰胺中联萘体系的电子跃迁矩之间的螺旋意义与从激子手性中得到的结果吻合得很好，这表明它可能应用于绝对构型的测定。2)在β位置上具有立体中心的伯醇衍生的2，2‘-联萘酯的诱导圆二色谱和构象分析中，在240nm处观察到了所有伯醇衍生的双标CD曲线。用分子力学方法对酯类进行了构象分析。在某些情况下，最稳定的顺时针或逆时针构象的2-萘酸酯基团的两个纵向跃迁力矩之间的螺旋感觉与从激子手性计算的结果不同。为此，采用含时密度泛函理论(TD-DFT)对底物官能团与2-萘甲酸酯的酯基之间具有强或中等相互作用的两个酯进行了CD计算和构象分析。结果表明，用TD-DFT方法测定联萘酯的绝对构型是非常有效的。

1) Circular dichroism in a chiral amide possessing an achiral bhaohthyl chromophoreThe bisignate CD curves were observed at around 240 nm in all binaphthyl amides examined. In a conformational analysis of the derivatives, a close correlation was observed between the signs of exciton chirality and the screw senses of the two 2-naphthoyl groups (positive/clockwise; negative/counterclockwise). A semi-empirical molecular orbital calculation (AM1) suggested an intramolecular hydrogen bonding. The CD spectra of the antipodal amides changed into split curves centered at 225 nm after N-methylation. Furthermore, the calculated screw senses between the electric transition moments of the binaphthyl system in N-methyl amides were in good accordance with those expected from their exciton chiralities, indicating a possible application for determination of absolute configuration.2) Induced circular dichroism and conformational analysis of 2.2'-binaphthyl esters derived from primary alcohols possessing a stereogenic center in the β-positionInduced bisignate CD curves were observed near 240 nm in all 2, 2'-binaphthyl esters derived from primary alcohols with a chiral center in the p-position of the hydroxyl group. Conformational analyses of the esters by molecular mechanics were performed. In some cases, the calculated screw sense between the two longitudinal transition moments of 2-naphthoate groups for the most stable conformer with clockwise or counterclockwise orientation was found to be different from that expected from their exciton chiralities. Therefore, CD calculations and conformational analyses of the two esters having strong or moderate interaction between the functional group of the substrate and the ester group of the 2-naphthoate were carried out by the time-dependent density functional theory (TD-DFT). The results suggested that the TD-DFT is strongly effective for determination of the absolute configuration of binaphthyl esters.