Constituents of commercial Labdanum oil

Commercial Labdanum oil contains more than 300 constituents. 186 compounds (154 from the neutral part, 32 from the acidic part), representing about 95% of the oil, were identified mainly by their NMR spectra. Typical for the Labdanum oil in the C15 to C20 region are aromadendrane (23%), cadinane (9%) and labdane (7%) derivatives, mostly oxidized. The main constituents in this region are ledene (92, 9.3%), allo‐aromadendrene (86, 1.5%), 1,5‐cis‐aromadendr‐9‐ene (91, 1.4%), viridiflorol (112, 4.3%), 1,2‐dehydroviridiflorol (104, 1.4%), ledol (116, 1.3%), palustrol (105, 1.2%), the new cubeban‐11‐ol (113, 4.1%), copaborneol (117, 1.8%), and ambrox® (137, 1.4%). The following new natural compounds were isolated: 1. C9→C14 compounds: 2,2,5‐trimethyloxepan‐4‐one (30), cis‐p‐menth‐4(8)‐en‐2‐ol (40), (2E,4E)‐6‐hydroxy‐2,6‐dimethylhepta‐2,4‐dienal (59), cis‐5‐hydroxymentha‐1(6),8‐dien‐2‐one (71), 7‐acetyl‐2,2,6‐trimethylbicyclo[4.2.0]octane (72), 4,4,7a‐trimethyl‐1,4,5,6,7,7a‐hexahydro‐2H‐inden‐2‐one (83), 6‐acetyl‐5,8,8‐trimethylbicyclo[3.2.1]octan‐2,3‐dione (119), 1,1,5,6‐tetramethyl‐1,2‐dihydro‐ (89) and 1,1,5,6‐tetramethyl‐1,2,3,4‐tetrahydronaphthalene (95). 2. Sesquiterpenes: cubeb‐11‐ene (82), 1,2‐dehydroglobulol (106), 1‐epi‐3,4‐dehydroviridiflorol (110), 3,4‐dehydroglobulol (118), muurola‐4,10(14)‐dien‐1‐ol (120), 5‐epi‐ (130) and 1,10‐seco‐aromadendran‐1,10‐dione (132), 5,11‐epoxycadin‐1(10)‐en‐9‐ol (136), 10‐hydroxycalamenene‐8,9‐epoxide (140) as well as 9(10→1)‐abeo‐9‐hydroxy‐aromadendran‐10‐one (131) named by us as 9‐hydroxy‐ladanifer‐10‐one, possessing a new skeleton. 3. Labdane derivatives: 7‐ (145), 8‐ (143) and 8(17)‐15‐nor‐labdene (142). 4. From the acidic part: 3‐isobutenyl‐5‐methyl‐5‐vinylbutyrolactone (M21), dimethyl (Z)‐2‐n‐hexyl‐3‐methylbutendioate (M24) and the two epimers of methyl 1,5,5‐trimethylbicyclo[4.1.0] heptan‐7‐carboxylate (M16, M,17). © 1998 John Wiley & Sons, Ltd.