[Thermodynamically controlled deracemization utilizing inclusion complexation].
Utilizing host-guest inclusion complexation in the solid state, alpha-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 alpha-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)-alpha-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.
Kaku
Hiroto
H
Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan. kaku@ph.bunri-u.ac.jp
D000470:Alkaloids / Q000138:chemical synthesis; D000818:Animals; D001952:Bridged-Ring Compounds / Q000138:chemical synthesis; D002625:Chemistry, Organic / Q000379:methods*; D001517:Coleoptera; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D013816:Thermodynamics; D008063:Thioctic Acid / Q000138:chemical synthesis
D000470:Alkaloids; D001952:Bridged-Ring Compounds; D007659:Ketones; C081529:epilachnene; D008063:Thioctic Acid