Solid State Structure of a Lithium Triorganostannate
Solid State Structure of a Lithium Triorganostannate
复制标题
三有机锡酸锂的固态结构
DOI：
10.1002/anie.198813811
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Fritz Töllner
中科院分区：
文献类型：
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作者：
M. Veith;Cornelius Ruloff;V. Huch;Fritz Töllner
在 1H-NMR 谱中可以清楚地区分（参见表 I），在（8d/9d）的情况下，核磁共振谱分配不再可能。所达到的选择性低于 1.5% ee，如通过比较释放的醇 (10d/ l l d ) 和参考化合物 (10d/ l ld)['21 由富集的 2-苯基丙二醇 12 (S : R = 3.3 : 1 2 54% ee) 制备的比旋光度所示。 250-MHz'H-NMR1I3l(1.1:1B 5.0%de)测定的(8~1·9~)比值也显着低于相应的甲醛非对映体(4~/5c)。通过此处提出的实验，可以表明通过甲醛结构可以进行具有可预测方向的不对称诱导（即使选择性随着链长的增加而略有降低）。如果从 1,10-不对称诱导的形式方面考虑反应，则实验上发现的 (4d/5d) 比率 2:1 (G 33% de) 是迄今为止我们已知的 1,10-不对称诱导的最高值。从基于立体电子效应的手性化合物 f3J 的自然相关系统的角度来看，左螺旋影响的反应方向基本上对应于 B 族缩醛基团（如 a-L-葡萄糖或 i3-D-葡萄糖的构型）诱导的反应方向。因此，α-D-葡萄糖（A 型的缩醛中心）与右旋甲醛螺旋也存在相关性。在潜在的生命起源条件下，在硅酸盐存在下，甲醛结构的实际出现，加上对映体纯螺旋的可预测特异性，使得光学活性多聚甲醛似乎在化学进化过程中的手性放大（永久）中发挥了作用。
clearly distinguishable in the 'H-NMR spectrum (see Table I), in the case of (8d/9d) a nuclear resonance spectroscopic assignment was no longer possible. The selectivity achieved was less than 1.5% ee, as shown by a comparison of the specific rotations of the liberated alcohols (10d/ l l d ) and the reference compound (10d/ l ld)['21 prepared from the enriched 2-phenylpropanediol 12 (S : R = 3.3 : 1 2 54% ee). The ratio of ( 8 ~ 1 9 ~ ) determined by 250-MHz 'H-NMR1I3l (1.1 : 1 B 5.0% de) was also significantly lower than that of the corresponding oxymethylene diastereomers ( 4 ~ / 5 c ) . l ' ~ ] With the experiments presented here it could be shown that an asymmetric induction with predictable direction (even with slightly decreasing selectivity with increasing chain length) is possible via an oxymethylene structure. If one considers the reaction from the formal aspect of a 1,nasymmetric induction then the ratio 2 : 1 ( G 33% de ) found experimentally for (4d/5d) is so far the highest value known to us for a 1,lO-asymmetric induction. From the point of view of a naturally related system of chiral compounds,f3J based on stereoelectronic effects, the direction of the reaction effected by a left helix corresponds fundamentally to that which is induced by an acetal group of the B family (configuration like a-L-glucose or i3-D-glucose). Consequently, there is also a correlation of a-D-glucose (acetalic center of the A-type) with a dextrorotatory oxymethylene helix. The actual occurrence of oxymethylene structures in the presence of silicates under potentially prebiotic conditions together with the predictable specificity of the enantiomerically pure helix make it seem possible that optically active paraformaldehyde has played a role in the amplification (perpetuity) of chirality in the course of chemical evolution.