Total Synthesis of (±)-Culmorin and (±)-Longiborneol: An Efficient Construction of Tricyclo[6.3.0.0<sup>3,9</sup>]undecan-10-one by Intramolecular Double Michael Addition
TMSCl-NEt(3)-ZnCl(2) caused the intramolecular double Michael addition to afford tricyclo[6.3.0.0(3, 9)]undecan-10-one 12 in high yields with perfect stereoselectivity. The methodology was further elaborated to achieve efficient totalsyntheses of (+/-)-culmorin (1) and (+/-)-longiborneol (2). The common precursor 13 of them was obtained from 14 in 94% yield as a single isomer by the treatment with LHMDS. After