Diterpenoids from Lycopus europaeus and Nepeta septemcrenata:: Revised structures and new isopimarane derivatives

Seven isopimarane diterpenoids have been isolated from Nepeta septemcrenata (3) and Lycopus europaeus (4-9), both species belonging to the Labiatae family. Compound 3 had been reported as the sole diterpene constituent of N, septemcrenata, whereas the physical and spectroscopic data of 4 were identical to those of a compound previously isolated from L. europaeus to which structure 1 had been attributed. As a result of exhaustive spectroscopic studies and some chemical correlations between 3 and 4, we definitely conclude that structure 1 must be amended to 4. In addition. the structures of five new diterpenoids found in L. europaeus (5-9) were established by chemical and spectroscopic means, and a normal isopimarane absolute configuration for all the isolated compounds, except for 7, was supported by CD data, application of the Horeau's method and chemical correlations. (C) 1999 Elsevier Science Ltd. All rights reserved.