54154-46-0Relevant academic research and scientific papers
Synthesis of cyclobakuchiols A, B, and C by using conformation-controlled stereoselective reactions
Kawashima, Hidehisa,Kaneko, Yuki,Sakai, Masahiro,Kobayashi, Yuichi
, p. 272 - 278 (2014)
Cyclohexanone with the pMeOC6H4 and CH 2/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. Control is key! Synthesis of cyclobakuchiols A and C was stereoselectively accomplished by conformation-controlled substitution of allylic picolinate with Me2CuMgBr×MgBr2/ZnI 2. On the other hand, cyclobakuchiol B was synthesized by stereoselective addition of the cyclohexanecarboxylate enolate to CH 2/CHSOPh (see scheme). Copyright
