Ferdinand Bohlmann

New germacranolides, guaianolides and rearranged Guaianolides from Lasiolaena santosii

Abstract The aerial parts of L. santosii afforded three new diterpenes, a phenylpropanol, three eudesmane derivatives, three germacranolides, seventeen guaianolides and four rearranged guaianolides of a, so far, unknown type. Furthermore, several known compounds were isolated. The structures of the new compounds, the separations of which caused difficulties, were elucidated by spectroscopic methods and by some chemical transformations. The chemotaxonomic situation is discussed briefly.

Neue kauren-derivate und melampolide aus Smallanthus uvedalia

Abstract The investigation of Smallanthus uvedalia afforded, in addition to known compounds, seven new kaurene derivatives and four melampolides. The structures were elucidated by spectroscopic methods. The chemotaxonomic situation is discussed briefly.

Modified eudesmanolides and other sesquiterpene lactones from Wunderlichia mirabilis and Actinoseris polymorpha

Abstract Re-investigation of Wunderlichia mirabilis afforded three new modified eudesmanolides of the same type isolated previously from an Onoseris species, and minute amounts of a germacranolide for which a structure only could be proposed. Actinoseris polymorpha also contained a new germacranolide, the angetate of desacetyllaurenobiolide. Structures were elucidated by spectroscopic methods and by some chemical transformations. The significance of these findings is discussed briefly.

Labdane derivatives from hemizonia species

Abstract The investigation of three Hemizonia species afforded in addition to known compounds seven new labdane derivatives, all derived from labd-13-en-15-ol. The absolute configuration of these diterpenes was determined by degradation of the triol by periodate cleavage, which afforded a known norditerpene ketone. From H. fitchii two new chromene esters and the cis-isomer of a known coumarate were isolated. H. congesta afforded in addition to labdane derivatives a hydroxycubebol.

New alicyclic diterpenes and ent-labdanes from gutierrezia solbrigii

Abstract The investigation of the aerial parts of Gutierrezia solbrigii afforded in addition to known compounds nine new ent-labdane derivatives, an aromatic ester and five alicyclic diterpenes. The structures were elucidated by highfield 1H NMR spectroscopy.

Clerodane derivatives fromDiplostephium

Abstract The aerial parts of D. floribundum afforded, in addition to known compounds, 10 new clerodane derivatives while D. ericoides gave 2β-hydroxyhardwickiic acid and widespread compounds. The structures were elucidated by high field NMR spectroscopy. The chemotaxonomic aspects are discussed briefly.

Biological Activity of Diterpenes

Various biological activities (Table 13 [pp. 489–490]) have been reported for plant diterpenes, principally from members of the Ericaceae, Euphorbiaceae, Lamiaceae, and Compositae. Each of the major diterpenoid classes from this last family will be discussed below in terms of its biological properties.

Compound Names, Structures, and Sources

The names (Table 1 [pp. 7–59]) and structures (Figure 1 [pp. 219–384]) of diterpenes reported from the Compositae are organized according to skeletal type following the sequence indicated in Figure 2 (p. 392). If a name was assigned to a structure at the time the compound was reported, that name was included in Table 1. Otherwise, the structure was given a name compatible with the names previously assigned to related compounds. If more than one name was applied in the literature to the same structure, usually the first-published name was included in Table 1, followed by additional names listed within brackets. The compound number listed with each name was used throughout this treatment when reference to the compound was made. Comments about a reported compound were also included in brackets on a line below the compound name. Usually these comments describe situations in which the name applied to the compound was incompatible with either the illustrated structure or the published spectroscopic data.

Diterpene Distribution: Compositae

Green plants possess (1) geranylgeraniol, the required precursor for both carotenoid and gibberellin biosynthesis, (2) the enzymatic machinery to cyclize geranylgeraniol (or its isomer) to ent-kaurene, and (3) the enzymes for the oxidation of ent-kaurene and other diterpene substrates (420). Normally, the steady-state concentration of the products of these pathways falls below the level of detectability of all but the most sensitive analytical instruments. By comparison, the compounds that are the focus of this review constitute an “abnormal” biosynthetic excess detectable in the form of resins. Often, general plant metabolism is isolated from these biologically active resins by the comparmentation of resin biosynthesis and storage within glandular trichomes.

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).