Santalanes

The bisabolyl cation (P10.1) is the key intermediate in the biosynthesis of the bergamotane, a- and (3-santalane families of terpenes. The biogenetic reactions involved in converting (P10.1) to the final products, are all enzyme mediated, but their chemistry follows the basic principles of carbocation mechanisms. Draw mechanisms to account for the formation of a-bergamotene (P10.2), a-santalene (P10.3) and (3-santalene (P10.4) from the cation (P10.1) and propose a structure for the intermediate (X) (Figure P10). 

Bisabolane, Bergamotane, Campherane, Santalane, and Related Tricyclic Sesquiterpenoids... 

An additional bond from C-2 to C-4 of campherenane formally leads to tricyclic a-santalane, the basic skeleton of some constituents found in sandalwood oil (oil of santal) with a woody, sweet, balsamic odor, used in perfumery and as a urinary antiinfective obtained from dried heartwood of the tree Santalum album (San-talaceae) grown in east India. Examples include (+)-( -a-santalol with a slight woody odor similar to cedar wood oil and (+)-(Ej-a-santalal, with a strong woody odor. 

Cleavage of the C-3-C-4 bond of farnesane and connection of new bonds from C-2 to C-4, C-3 to C-7 and C-1 to C-4 lead to bicyclic p-santalane, which is another basic skeleton of substances found in sandalwood. Examples are (-)-p-santalene and (-)-( -p-santalol with a pleasant woody, slightly urinary odor used in perfumes and detergents... 

Of the other skeletal types shown in Fig. 8.1.10 bergamotane type (161) has not, apparently, yet been isolated from woody tissues. Santalane type is represented by sesquiterpenoids from Indian sandalwood oil, which is obtained by steam distillation of wood of Santalum album. Important constituents are a- and )ff-san-talene (182,183), and the derived allylic alcohols 184,185 which constitute almost 90% of the essential oil (71, 98, 238, 242). It may be noted that a-santalene was the first sesquiterpene for which the correct structure was proposed (344). 

According to Semmler cedrenol stands in the same relation towards cedrene as the two primary alcohols of the santalol series towards the sesquiterpenes, Cig 4, the santalanes and as myrtenol and the ginger-grass alcohol stand towards pinene and limonene. The primary CHjOH group in the cedrenol molecule occupies the same position which is occupied by the GH, group in cedrene and in solid cedrol. Hence the relation of cedrene towards cedrol and cedrenol is as follows... 

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