Antimitotic diterpenoids from Erythropodium caribaeorum: isolation artifacts and putative biosynthetic intermediates

Two new natural products, caribaeorane (12) and 15-hydroxycaribaeorane (11), have been identified in Erythropodium caribaeorum extracts by isolation of their C-4 methylketals 10 and 9. It has been demonstrated that eleutherobin (1) is an isolation artifact. A proposal for the late stages of the biosynthetic pathway to the E. caribaeorum antimitotic diterpenoids is presented.