Cembrane Cembrene

The separation and collection of the violet zone (Rj 0.98) of fraction 1 led to the isolation of m- and p-camphorene (compound 4 and compound 5) and cembrane A as well. Thongh m- and p-camphorene are taxonomic marker substances of the species B. serrata, it is pointless to use them in TLC, because the corresponding violet spot on the chromatogram of B. carterii stands for verticilla-4(20),7,l 1-triene, the taxonomic marker substance of B. carterii and cembrene A, too. These violet snbstances shonld be reserved for GC investigations. 

Frankincense, also called olibanum, is a natural oleo gum resin that exudes from incisions in the bark of Boswellia trees [46, 47]. Diterpenes like incensole or isoincensole and their oxide or acetate derivatives (see Figure 10.3) are characteristic biomarkers of olibanum [48]. Although diterpenoid hydrocarbons possessing the cembrane skeleton have been isolated from a variety of terrestrial and marine organisms, their occurrence and particularly that of cembrenes A and C (see Figure 10.3) is supplementary proof of the presence of olibanum in a sample. Optimisation of the SPME conditions was done with the aim of trapping these low volatile diterpenes. 

Characteristic to some important cembrane diterpenoids, such as isocembrene, cembrene, cembrene C, and sarcophytol A, is a 1,3-diene unit in the macrocyclic skeleton. In continuation of our ongoing project on the total synthesis of cembrane-type diterpenoids, we intended to explore a novel macrocyclization method to... 

Thus, an efficient and convergent total synthesis of ( )-isocembrene has been accomplished in seven steps from the known geranylacetone through an intramolecular Stille cross-coupling reaction. The strategy is of great potential for the divergent synthesis of complex cembrane-type diterpenoids such as cembrene-C and sarcophytols. 

A similar cyclization generates the 14-membered skeleton of cembrane from which other polycyclic diterpenes are derived. 3,7,11,15-Cembratetraene, better known as cembrene A, emerges directly from geranylgeranylpyrophosphate (Fig. 2) involving the 1,14-cyclization of the resulting allylic cation... 

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