Abietanes and Totaranes

Abietanes may formally be derived from pimaranes by migration of the methyl group C-17 from C-13 to C-15. In plants, however, they emerge from cyclization of geranylgeranyl diphosphate. Related parent diterpene hydrocarbons include 13,16-cycloabietanes, 17(15-16)-aZ)eo-abietanes in which the methyl group C-17 has shifted from C-15 to C-16, and totaranes. The latter formally arise from abietane when the isopropyl group migrates from C-13 to C-14. 

More than 200 diterpenes with an abietane skeleton are reported to exist naturally Numerous representatives oeeur in conifers. Selected examples include palustra-diene, also referred to as (-)-8,13-abietadiene, from the pine tree Pintds palustris, from the so-called berries of the sade tree Juniperus sabina (Cupressaceae) and other species of juniper trees, (-)-abietenol from the pine Pinus silvestris and the fir Abies sibirica, (-)-abietic aeid belonging to the resin acids of turpentine and wide-spread in conifers such as various pines Pinus), larch trees Larix) and firs Abies), as well as (+)-palustric acid from the balm and the roots of Pinus palustris, isolated from gum rosin. 

Other abietane derivatives with benzenoid ring C are among the active substances in some well-known medicinal herbs. The parent hydrocarbon (-)-8,l 1,13-abieta-triene occurs in the pine tree Pinus pallasiana (Pinaceae). (+)-Camosolic acid and the 20,7p-lactone (-olide) of its hydroxy-derivative referred to as camosol belong to the bitter substances of the oil of sage from Salvia camosa (Labiatae) and related species. (-)-Rosmanol, a 20,6p-lactone, is an antioxidant isolated from the leaves of rosemary Rosmarinus officinalis (Labiatae), which also contain camosol. 

More than 20 quinoid 13,16-cycloabietanes, named as eoleones A-Z, oeeur in the yellow glands in the leaves of Afriean Coleus speeies (Labiatae). Lanugone A isolated from Plectranthus lanuginosis (Labiatae) represents a quinoid n(lS)-abeo-abietane. Totaranes sueh as (-l-)-totarol and the derived biphenyl-type dimer (-t)-podototarine are found in the wood of Podocarpus totara (Cupressaeeae). 

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