Constituents of commercial Labdanum oil

Abstract

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.