title: Oxidative homocoupling of chiral 3-arylpropanoic acid derivatives. Application To asymmetric synthesis of lignans
abstract: The oxidative homocouplings of lithium enolates of (4S)-3-(3-arylpropanoyl)-4-isopropyl-2-oxazolidinones and (4R, 5S)-1-(3-arylpropanoyl)-3,4-dimethyl-5-phenyl-2-imidazolidinones gave the corresponding R,R-dimers stereoselectively with TiCl(4), PhI(OAc)(2), or CuCl(2) as an oxidant. The stereoselectivity can be explained by a radical coupling mechanism. Optically active dibenzylbutyrolactone lignans, such as (-)-hinokinin and (-)-dimethylmatairesinol, and dibenzylbutanediol lignans, such as (-)-dihydrocubebin and (-)-dimethylsecoisolariciresinol, were synthesized from the major R,R-dimers. The oxidative coupling of (4R, 5S)-1-(3-arylpropanoyl)-3,4-dimethyl-5-phenyl-2-imidazolidinones with LDA-I(2) gave R,S-dimers mainly, and this result can be explained by an S(N)2 mechanism.
authors.affiliation: Department of Biotechnology, Faculty of Engineering, Tottori University, Tottori 680-0945, Japan.
authors.initials: N
authors.lastname: Kise
authors.initials: T
authors.lastname: Ueda
authors.initials: K
authors.lastname: Kumada
authors.initials: Y
authors.lastname: Terao
authors.initials: N
authors.lastname: Ueda