New abietane diterpenoids from the roots of Salvia przewalskii

In an antibiotic screening program for new drug leads, we discovered a seco-norabietane diterpenoid with an unprecedented carbon skeleton, salprzelactone (1), together with three new abietanoids (2–4) from the roots of Salvia przewalskii. Their structures were mainly elucidated by NMR and MS data. The structures of 1 and 4 were elucidated by comprehensive spectroscopic and a single-crystal X-ray crystallographic analysis with the absolute configuration determined by the CD approach coupled with theoretical CD spectra. Those compounds were evaluated for their antibacterial activities against six bacteria.