Structures of three new diterpenoids from Ballota species
Abstract
Ballonigrin and ballonigrinone, isolated from B. rupestris, have been shown to be 15,16-epoxy-7-oxolabda-8(9),13(16),14-trien-19,6β-olide (1) and the corresponding 3-ketone (2). 7α-Acetoxymarrubiin (5) has been isolated from B. nigra.