Synthesis of Natural Oxygenated Monocarbocyclic Sesquiterpenoids from 6,7-Epoxygeranyl Acetate

Natural sesquiterpenes 5-(2′,5′-epoxy-2′,6′,6′-trimethyl)cyclohexyl-3-methyl-1-penten-3-ol (5), cis-3-[(E)-5′-hydroxy-3′-methyl-3′-pentenyl]-2,2-dimethyl-4-methylenecyclohexanol (elegansidiol) (6), 4-(5′-acetoxy-2′,6′,6′-trimethyl)cyclohex-2′-enyl-3-methyl-1-penten-3-ol (7) and 5-acetoxy-3-(3-hydroxy-3-methylpent-4-enyl)-2,4,4-trimethylcyclohex-2-enone (8) were prepared from 6,7-epoxygeranyl acetate (9), via (2′,5′-epoxy-2′,6′,6′-trimethyl)cyclohexylmethyl tosylate (10), for the first time. 5 is an intermediate in the synthesis of the sesquiterpene-coumarin ether (±)-farnesiferol C (1). The preparation of suitable intermediates for synthesising related natural farnesiferol B (3) and D (4) is also reported.