Structure and absolute configuration of new diterpenes from Lavandula multifida.

Four new diterpenes (1-4) have been isolated from the aerial parts of Lavandula multifida, together with the known compound glutinosin (5). The structures of these compounds were identified on the basis of extensive NMR studies as 15,16-dihydroxy-7,11-dioxopimar-8(9)-ene (1), 15S,16-dihyroxy-7-oxopimar-8(9)-ene (2), 15,16,17-trihydroxy-7-oxopimar-8(9)-ene (3), and 15,16,17-trihydroxypimar-8(9)-ene (4). The absolute configuration of the 15,16-diol moiety in 1-5 was determined observing the circular dichroism induced after addition of dimolybdenum tetracetate in DMSO solution.