title: Synthesis of cyclobakuchiols A, B, and C by using conformation-controlled stereoselective reactions.
abstract: Cyclohexanone with the pMeOC6H4 and CH2=C(Me) substituents at the C3 and C4-positions was prepared from (+)-β-pinene and converted to the allylic picolinate by a Masamune-Wittig reaction followed by reduction and esterification. Allylic substitution of this picolinate with Me2CuMgBr·MgBr2 in the presence of ZnI2 proceeded with γ regio- and stereoselectively to afford the quaternary carbon center on the cyclohexane ring with the CH2=CH and Me groups in axial and equatorial positions, respectively. This product was converted to cyclobakuchiol A by demethylation and to cyclobakuchiol C by epoxidation of the CH2=C(Me) group. For the synthesis of cyclobakuchiol B, the enantiomer of the above cyclohexanone derived from (-)-β-pinene was converted to the cyclohexane-carboxylate, and the derived enolate was subjected to the reaction with CH2=CHSOPh followed by sulfoxide elimination to afford the intermediate with the quaternary carbon center with MeOC(=O) and CH2=CH groups in axial and equatorial positions. The MeOC(=O) group was transformed to the Me group to complete the synthesis of cyclobakuchiol B.
authors.affiliation: Department of Bioengineering, Tokyo Institute of Technology, B52, Nagatsuta-cho 4259, Midori-ku, Yokohama 226-8501 (Japan), Fax: (+81) 45-924-5789.
authors.forename: Hidehisa
authors.initials: H
authors.lastname: Kawashima
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kaneko
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sakai
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kobayashi
mesh_terms: D000893:Anti-Inflammatory Agents / Q000138:chemical synthesis* / Q000737:chemistry; D000081008:Bicyclic Monoterpenes; D001643:Bridged Bicyclo Compounds / Q000737:chemistry; D003510:Cyclohexanes / Q000138:chemical synthesis* / Q000737:chemistry; D003512:Cyclohexanones / Q000737:chemistry; D004852:Epoxy Compounds / Q000737:chemistry; D004951:Esterification; D039821:Monoterpenes / Q000737:chemistry; D010636:Phenols / Q000138:chemical synthesis* / Q000737:chemistry; D029907:Psoralea / Q000737:chemistry / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D000893:Anti-Inflammatory Agents; D000081008:Bicyclic Monoterpenes; D001643:Bridged Bicyclo Compounds; D003510:Cyclohexanes; D003512:Cyclohexanones; D004852:Epoxy Compounds; D039821:Monoterpenes; D010636:Phenols; C000590877:cyclobakuchiol A; C000590878:cyclobakuchiol B; C000590879:cyclobakuchiol C; C010789:beta-pinene; C036468:cyclohexanone
keywords: allylic substitution; asymmetric synthesis; copper; magnesium; synthesis design