Labdanolic acid

Labdanum resin (from the Cistaceae family) contains diterpenoid compounds with a labdane-type structure, namely laurifolic, cistenolic and labdanolic acids [100 103]. 

Clerodanes.—In a study of South African Macowania species, a cis-clerodane acid (28) and labdanolic acid were obtained from M. glandulosa. Deoxymarrubialac-tone (29) has been isolated from Chaiturus marrubiastrum. Linarienone (30) is another ds-fused clerodane which has been obtained from the roots of Linaria japonica (Scrophulariaceae) and correlated with linaridial. The bacchotricuneatins A (31) and B (32) are two new diterpenoid lactones which were isolated from Baccharis tricuneata (Astereae) and whose structures were determined by a combination of spectra and X-ray analysis. 

From the plant Agathis robusta a group of labdane isomers at C-13 have been isolated and related to 13-e/n-manool after interconvertion using lithium in diaminoethane [110]. The Hymenaea species, i.e H. ablongifolia and H. parvifolia, have been studied and enantiopinifolic acid as well as guamaic acid have been isolated, while enantio-13-ep/-labdanolic acid has been isolated from Trachylobium verrucosum [111]. 

It should be mentioned that authors [72] synthesised the acetoxy aldehyde (53) from labdanolic acid (6) in 5 steps in an overall 50 %... 

To convert labdanolic acid (8.27) to the naphthofuran (8.10), it is necessary to shorten the side chain and then cyclise the residue onto the alcohol to form the furan ring. In this synthesis, Bolster and de Groot carried out the chain shortening in two steps.816 Firstly, after protection of the ring hydroxyl group by conversion to the acetate, the terminal acidic carbon atom was removed by photo-decarboxylation in the presence of iodine and iodobenzene diacetate. This gave the iodinated material (8.29). Treatment of (8.29) with potassium tert-butoxide... 

The Clerodane Series.—Some further contributions have been made to the chemo-taxonomy of Cistus species. Whereas C. labdaniferus contains mainly labdanes such as labdane-8a,I5,l9-triol, C. monspeliensis contains a group of clerodane diterpenoids whose structures are summarized in (17), together with labdanolic acid and labdane-8a,15-diol. 

Isopilopic acid, A28 Labdanolic acid, T36 -longifolic acid, T28... 

Labdanum gum and concrete contain volatile oil, paraffins, and resins. The resins consist of acidic constituents (e.g., labdanolic acid, 6-oxo-cativic acid, cinnamic acids, anisic acid, arachic acid, behenic acid butyric, malo-nic, and oxalic acids) and neutral labdane compounds (e.g., labdane-8a,15-diol, labdane 8a,15,19a-triol, 15-nor-8-labdanol, labd- 8(17)-en-15-ol, and 15-hydroxy-7-lab-... 

Castro, J.M., Salido, S., Altarejos, J., Nogueras, M., Sinchez, A. Synthesis of Ambrox from labdanolic acid. Tetrahedron. 52 (29), 5941-5949, 2002. 

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