Novel Sesquiterpene Lactones from Callitris columellaris Heartwood

Abstract

Five new sesquiterpene lactones, callitrin (1) (an elemanolide), callitrisin (2) and dihydrocallitrisin (6) (eudesmanolides), and columellarin (4) and dihydrocolumellarin (5) (guaianolides) have been isolated from Callitris columellaris heartwood along with the germacranolide (3) which is a new natural product previously only known synthetically. These compounds are the first sesquiterpene lactones isolated from the Cupressaceae. Lactones (1), (2) and (6) all share a novel cis-fused lactone ring in which the C7-C11 bond is axial to a cyclohexane ring.