Ent-Pimarane

Lastly, tedanol isolated from a Caribbean Tedania ignis collected in the mangroves of Sweeting Cay, Grand Bahama Island, is a brominated and sulfated diterpene with ent-pimarane skeleton. This original diterpene displays potent anti-inflammatory activity by inhibition of COX-2 (cyclooxygenase 2) expression thus, tedanol appears as a non-steroidal anti-inflammatory (Costantino et al, 2009b). 

Costantino, V, Fattorusso, E., Mangoni, A., Perinu, C., Cirino, G., De Gruttola, L., and Roviezzo, F. (2009b) Tedanol A potent antiinflammatory ent-pimarane diterpene from the Caribbean sponge Tedania ignis. Bioorg. Med. Chem., 17, 7542-7547. 

Pimarane diterpenes with an antipodal backbone have been isolated from Cleistanthus schlechteri. These included ent-3)8-hydroxypimara-8,l5-diene, ent-3)3,12 -dihydroxypimara-8,l 5-diene (16), and the corresponding C-12 ketone. The location of the carbonyl group at C-12 was inferred from bromination and dehydrobromination and from the multiplicity of the C—H resonance of the C-12 alcohol. Macarangonol (17) has been isolated from Macaranga tanarius. 

A group of diterpenes with the pimarane skeleton (1). In R, the methyl group at C-10 is cis to the ethyl group at C-13, whereas in the isopimaranes it is in the transposition. Both enantiomers of not only the R but also of the isopimaranes occur in nature. R are formed by a further cyclization of the labdane skeleton. Examples are annonalide, momilactones A and B (both growth inhibitors for plants ), leucophleol and ent-8(14),15-pimaradiene. In the past the R were also known as sandaracopimaranes. 

The most common pimarane-type acids are pimaric, isopimaric and sandaracopimaric acids (Fig. 4.3). Compared with the abietic counterparts, not only is the basic skeleton diffa-ent but, more importantly, the double bond system is now not conjugated, a fact which reduces significantly the possible chemical exploitation of these compounds. 

Thermarol (525), a new -pimarane-type diol, has been isolated from Jungermannia species, together with the previously known ent-pimara-8(14),15-dien-19-ol (524) and -pimara-8(14),15-dien 19-oic acid (526) 249), Diol (525) was acetylated to give a monoacetate, which on dehydration afforded a tricyclic diene identical with -pimara-8(9),15-dien-19-yl acetate prepared by isomerization of the acetate of (524) with formic acid. Position and stereochemistry that the tertiary hydroxyl group of (525) was at C-8 and a was deduced by comparing of the C-NMR spectra of (524—526) and the pyridine-induced solvent shifts of C-18 and C-20 methyl signals in the H-NMR spectra of (525) and (526). 

Figure 15. Proposed biogenetic routes for tricyclic e /-pimarane, e /-abietane, erythroxane, cleistanthane and isocleistanthane diterpene skeletons derived from ent-labdane precursors.

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