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

1)具有非手性二羟苯基发色团的手性酰胺的圆二色性在所检测的所有二羟苯基酰胺中，在约240 nm处均观察到双色CD曲线。在衍生物的构象分析中，观察到激子手性的符号与两个2-萘基的螺旋感密切相关（正/顺时针；负/逆时针）。半经验分子轨道计算（AM1）表明存在分子内氢键。经n -甲基化后，对映酰胺的CD光谱呈以225 nm为中心的分裂曲线。此外，计算得到的n -甲基酰胺中二萘基体系的电跃迁矩之间的螺旋感觉与从它们的激子手性中得到的结果很好地吻合，这表明它可能用于确定绝对构型。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性和构象分析。在近240 nm处，所有手性中心位于羟基p位的伯醇衍生的2,2′-联萘酯均观察到诱导双色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，顺时针或逆时针方向最稳定的2-萘酸基团的两个纵向跃迁矩之间的螺旋意义与它们的激子手性所期望的不同。因此，利用时间依赖密度泛函理论（TD-DFT）对底物官能团与2-萘酸酯官能团之间具有强或中等相互作用的两种酯进行CD计算和构象分析。结果表明，TD-DFT对测定二萘酯的绝对构型具有较强的有效性。

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.