Generation of (+)-Prezizanol, (+)-Prezizaene, and the ent-β-Isopipitzol Framework via Cationic Rearrangement of Khusiol and Related Compounds

Treatment of the tosylate of khusiol with lithium carbonate in aqueous 1,4-dioxane affords, via a Wagner-Meerwein rearrangement, (+)-prezizanol. POCl₃/pyridine-mediated dehydration of (+)-prezizanol then gives (+)-prezizaene. More direct and efficient routes to this last compound were achieved by treating either khusiol or its C8 epimer with POCl₃/pyridine. Under related conditions, a cyclic sulfate is converted, by a high yielding process, into an alcohol that embodies the decahydro-1,7-methanonaphthalene framework.