Pimarane, structure

About 80% of the diterpene acids of the genus Finns have an abietane skeleton, with abietic acid (structure 3) as the predominant component. Other diterpene acids have a pimarane skeleton (structure 4). All compounds with the abietane skeleton are distinguished by the presence of an isopropyl group. 

In general, very little has been written about diterpenes from the Latin American Celastra-ceaeas these structures are not often found. Abietriene type diterpenes have been the general rule in the Celastraceae although the chemical study of the minor constituents of Orthosphenia mexicana and Rzedowskia tolantonguensis did enable pimarane type diterpenes to be isolated and chemically characterized [43,45] and the second of these species afforded a series of new diterpenes with an isopimarane skeleton, described for the first time in the Celastraceae. 

Another new pimarane diteipenoid salvipimarone (7P-hydroxy-3,ll-dioxo-pimara-8(14),15-dien) (55) was isolated from S. multicaulis Vahl.. The structure of salvipimarone was deduced fix>m ID and 2D NMR spectra. The compound was found to have the molecular formula C20H28O4 ijn/z 332.1991). The H NMR spectrum indicated its ethylenic side chain by signals at 5 5.79 (IH, dd, J=11... 

Figure 4.3 Structures of the most common pimarane-type resin acids.

Colophony is a complex mixture of resin acids (about 90%) and neutral substances, i.e. diterpene alcohols, aldehydes and hydrocarbons (about 10%). Its composition varies with the species from which it is obtained and also depends on the recovery processes and storage conditions. The acids are diterpenoid acids, of which the abietane- and pimarane-type structures are the most abundant (Fig. 1). Tail-oil rosin contains less abietane-type acids and more dehydroabietic acid than gum rosin does. This is due to oxidation-... 

When normal- and /-series structures co-occur it is usually as a mixture of normal-labdanes and some tri- or polycyclic wMabdane derivatives. Normal-series structures infrequently exist as tri- or polycyclics the most common of such structures, the normal-pimaranes (sandaracopimaranes), achieve prominence only within the small tribe Calenduleae. 

Figure 28. Structures of wMabdane (430, 447-449), e /-pimarane (976), ew/-abietane (614), ew/-helifiilvane (796-799), e /-trachylobane (791), en/-atisirane (783), enU stachane (764, 765, 767, 770, 771, 774) (Scheme A), and ewMcauranoid (Scheme B) diterpenes reported from Helichrysum (Inuleae).

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