Antibacterial diterpenoids from Fabiana densa var. ramulosa.

A biologically monitored fractionation of the resinous exudate of Fabiana densa Remy var. ramulosa Wedd. led to the isolation of the two new diterpenes: ent-beyer-15-en-18-O-succinate and ent-beyer-15-en-18-O-oxalate as the unique compounds responsible for the observed antibacterial activity of this extract. Their structures were determined by 1D and 2D NMR spectroscopy.