Bioinspired Total Synthesis of 3- epi -Junipercedrol.

A bioinspired total synthesis of 3- epi -junipercedrol, which contains a strained tricyclo[5.2.2.0 3,7 ]undecane allo -cedrane framework and five stereocenters, was accomplished via an effective anionic semipinacol rearrangement of a tricyclic cedrane mesylate. The corresponding cedrane precursor was synthesized efficiently by employing the reductive oxy-Nazarov cyclization and an intramolecular aldol condensation as the key steps. This synthetic approach provided a further evidence for the biogenetic relationship between the typical cedrane and allo -cedrane sesquiterpenoids.