title: Asymmetric synthesis of neolignans (-)-epi-conocarpan and (+)-conocarpan via Rh(II)-catalyzed C-H insertion process and revision of the absolute configuration of (-)-epi-conocarpan.
abstract: Catalytic asymmetric synthesis of neolignan natural products (-)-epi-conocarpan and (+)-conocarpan has been achieved by exploiting an enantio- and diastereoselective intramolecular C-H insertion reaction to construct a cis-2-aryl-2,3-dihydrobenzofuran ring system as a key step. The C-H insertion reaction of 5-bromoaryldiazoacetate catalyzed by Rh(2)(S-PTTEA)(4), a new dirhodium(II) carboxylate complex that incorporates N-phthaloyl-(S)-triethylalaninate as chiral bridging ligands, provided 2-aryl-5-bromo-3-methoxycarbonyl-2,3-dihydrobenzofuran with exceptionally high diastereoselectivity (cis/trans = 97:3) and high enantioselectivity for the cis isomer (84% ee).
authors.affiliation: Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Natori
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Tsutsui
authors.forename: Naoki
authors.initials: N
authors.lastname: Sato
authors.forename: Seiichi
authors.initials: S
authors.lastname: Nakamura
authors.forename: Hisanori
authors.initials: H
authors.lastname: Nambu
authors.forename: Motoo
authors.initials: M
authors.lastname: Shiro
authors.forename: Shunichi
authors.initials: S
authors.lastname: Hashimoto
mesh_terms: D001572:Benzofurans / Q000138:chemical synthesis*; D002384:Catalysis; D017705:Lignans / Q000138:chemical synthesis*; D015394:Molecular Structure; D012238:Rhodium; D013237:Stereoisomerism
chemical_list: D001572:Benzofurans; D017705:Lignans; C447284:conocarpan; D012238:Rhodium