熱力学的な平衡条件下での包接分子認識現象を利用したデラセミ化法の開発

抄録

  Utilizing host-guest inclusion complexation in the solid state, α-monosubstituted ketones were deracemized using optically active host compounds such as (−)-trans-2,3-bis(hydroxydiphenylmethyl)-1,4-dioxaspiro[5.4]decene (1a) under alkali conditions. This new method afforded optically active α-monosubstituted ketones in excellent yields with high enantiomeric excesses. For example, (±)-2-benzylcyclohexanone (2a) and (±)-3-benzylhexan-2-one (3c) were converted to the R-isomer (74% ee) and the S-isomer (96% ee), respectively, in quantitative yields. An x-ray crystallographic study elucidated the structure of the inclusion complex of 1a and (R)-2a. The study showed that the host molecules 1a ingeniously includes the guest molecule (R)-2a via hydrogen bonding and van der Waals interactions. As an application of deracemization, coenzyme (R)-α-lipoic acid and (R)-(−)-epilachnene, the antipode of an defensive droplets from the Mexican bean beetle, Epilachna varivestis, were synthesized in short steps with>99% ee and 87% ee, respectively.