Diterpene Analysis with Emphasis on Clerodanes

Early work on Compositae diterpenes focused on Solidago and the normal-labdane, solidagenone (Figure 33 [pp. 513–514]; Structure 158) (9, 16, 17). Later, ent-clerodanes (kolavanes) were found to co-occur with the labdanes (364, 365). The first identified novel clerodane, solidagonic acid (Figure 33; Structure 500), was shown by chemical interconversion (364, 365; Figure 33) to share the orientivity of the major chiral centers, C-5, C-8, C-9, and C10, with the co-occurring clerodanes of known stereochemistry, kolavenic acid (495) and kolavenol (Figure 33; Structure 475).