Murai S, Soutome T, Yoshida N, Osawa S, Harada N
Institute for Chemical Reaction Science, Tohoku University, Sendai, Japan.
Enantiomer. 2000;5(2):197-202.
2,6-Dimethylspiro[3.3]heptane-2,6-dicarboxylic acid (2), an analog of the Fecht acid (1), was enantioresolved by the method of (1S,2R,4R)-(-)-2,10-camphorsultam yielding enantiopure acid (+)-2, the S absolute configuration of which was unambiguously determined by X-ray crystallography of camphorsultam amide derivative (R)-(-)-12b and chemical correlation. To determine the absolute configuration of chiral spiro[3.3]heptane compounds by the circular dichroism (CD) exciton chirality method, acid (+)-2 was converted to (+)-2,6-bis(phenylacetylenyl)-2,6-dimethylspiro[3.3]heptane (3) and (+)-2,6-bis(4-methoxyphenylacetylenyl)-2,6-dimethylspiro[3.3]heptane (4). The CD spectra of (+)-3 and (+)-4 exhibit intense exciton split Cotton effects of positive chirality, from which their S absolute configurations were confirmed.
2,6 - 二甲基螺[3.3]庚烷 - 2,6 - 二甲酸（2），作为费希特酸（1）的类似物，通过(1S,2R,4R)-(-)-2,10 - 樟脑磺内酰胺法进行对映体拆分，得到对映体纯的酸(+)-2，其S绝对构型通过樟脑磺内酰胺酰胺衍生物(R)-(-)-12b的X射线晶体学和化学关联明确确定。为了通过圆二色性（CD）激子手性方法确定手性螺[3.3]庚烷化合物的绝对构型，将酸(+)-2转化为(+)-2,6 - 双（苯乙炔基）-2,6 - 二甲基螺[3.3]庚烷（3）和(+)-2,6 - 双（4 - 甲氧基苯乙炔基）-2,6 - 二甲基螺[3.3]庚烷（4）。(+)-3和(+)-4的CD光谱显示出强烈的正手性激子分裂科顿效应，由此确认了它们的S绝对构型。
