Synthesis of R-(−)-Imperanene from the Natural Lignan Hydroxymatairesinol

Abstract
A convenient and high yielding method for the synthesis of R-(−)-imperanene, starting from the readily available natural lignan hydroxymatairesinol from Norway spruce, was developed. Hydroxymatairesinol was degraded in strongly basic aqueous conditions to (E)-4-(4-hydroxy-3-methoxyphenyl)-2-(4-hydroxy-3-methoxyphenylmethyl)but-3-enoic acid, which was esterified and then reduced by LiAlH4 to afford R-(−)-imperanene. The configuration at the crucial stereocenter was preserved in the synthesis, and the obtained product was identified by optical rotation measurements and chiral HPLC analyses as the R-(−)-enantiomer (ee 86−92%).