Absolute configuration of the (+)-calamenenes: crystal structure of 7-hydroxycalamenene

Abstract

The sesquiterpenes 7-hydroxycalamenene and (+)-calamenene isolated from Eremophila drummondii have been interrelated. The crystal structure and absolute configuration of the p-bromobenzoate of 7-hydroxycalamenene, C₂₂H₂₅BrO₂, has been determined; crystals are orthorhombic, space group P2₁2₁2₁, unit cell dimensions a= 9.471(5), b= 11.469(5), c= 18.253(7)Å, for Z= 4. These results show that both sesquiterpenes have the (1R,4R)-configurations and resolve the present confusion on this point.