Seco-LABDANE

The structure of the epoxy-dialdehyde (15), from Afromomum daniellii (Zingiberaceae), was established by correlation with c -12-norambreinolide. The hydroxy-acid (16), salvic acid from Eupatorium salvia,and the ring B seco-labdane jhanic acid (17) from Eupatorium jhanii are two further diterpenoids from these species of the Compositae. The structure of the latter rests on interpretation of the H and C n.m.r. data. Gutierrezia lucida (Compositae) contains the 13-epimeric acids (18) related to agathic acid together with the butenolide (19). Some esters of 6-hydroxylabdane-17-carboxylic acids were detected in G. mandonii. The investigation of Cistus species has continued. The ent-labdane acetyl-laurifolic acid (20) is a component of Cistus laurifolius ... 

Warning, U., J. Yakupovic, D. Friedrich, V. Castro, and F. Bohlmann Further Seco-Labdanes from Hebeclinum macrophyllum. Phytochem., 26, 2335 (1987). 

Bohlmann, F., M. Wallmeyer, and J. Jakupovic A new seco-labdane derivative from Athrixia data. Phytochrem. 21, 1806 (1982). 

Four bicyclic type diterpenoids have been reported from Salvia species labdanes, neo-clerodanes and clerodanes, seco-clerodanes, rearranged clerodanes. 

Figure 1. Structures of Diterpenes 27. Nomial-Labdane-20,12-Lactone, 5,10-Seco-... 

Figure 7. Proposed route of biogenesis of the 5,10-seco-normal-labdanes, 225-230, from a common precursor (similar to 214) occurring in Nidorella hottentotica 155).

The two carbon skeletons of ent-labdane and spongiane (=aplysane) are known, and we suggest that the odier two were named with regard to die corresponding derivatives already published verrucosane and seco-... 

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