Scopadulane-type diterpenoids

Because of such a unique carbon skeleton and many-sided biological activities, the scopadulan-type diterpenoids were selected as attractive targets for chemical synthesis and their total syntheses were accomplished by Overman et at., Ziegler et at. and Tagat et at.. 

SDB and SDC, scopadulan-type diterpenoids, showed cytotoxicity, anti-HSV-1 activity and inhibitory effects on histamine-induced gastric acid secretion and PTH-stimulated bone resorption. 

Scopadulan-type diterpenoids were supposed to be biosymthesized through similar route to that of aphidicolin. However, a non-mevalonate pathway was considered to be involved in this biosynthetic pathway. 

Furthermore, possible biosynthetic pathway of scopadulan type and related tetracyclic diterpenoids in S. dulcis was proposed. 

Whole plants of Scoparia dulcis collected in Paraguay were extracted with 70% EtOH at boiling temperature. The extract was partitioned between CHC13 and H2O and the CHC13 soluble part was further fractionated by combination of column chromatography on silica gel and HPLC method using reversed phase ODS column. As a result, three types of diterpenoids were isolated, i.e., labdane-type scoparic acids A (SA, 1), B (SB, 2), and C (SC, 3), scopadulan-type scopadulcic acids A (SDA, 4) and B (SDB, 5), and aphidicolan-type scopadulin (SD, 6). On the other hand, scopadiol... 

SDX, 7, labdane-type) and scopadulciol (SDC, 8, scopadulan-type) were newly isolated from Formosan collection of this plant. It is interesting that all isolated diterpenoids possess a benzoyl group in the molecule as shown in Fig. (1). In addition, quantitative HPLC analyses of diterpenoids in individual plants collected in Paraguay, Taiwan, China, Indonesia and Thailand revealed that there are three chemotypes in this plant as to the major component, i.e., SDB type, SA type and SDX type [21,22]. 

BIOSYNTHESIS OF SCOPADULAN-TYPE AND RELATED TETRACYCLIC DITERPENOIDS... 

---