Kaurene-type diterpenoids

Fig. (27). Anti-HIV kaurene type diterpenoids from Tripterigium wilfordii...

The distribution of diterpenoids in five Rabdosia umbrosus varieties has been investigated from the chemotaxonomic point of view 96) R. umbrosa var. umbrosa, R. umbrosus var. hakusanensis, R. umbrosus var. latifolia, R. umbrosus var. excisinflexa, and R. umbrosus f. kameba were studied by reverse phase HPLC (97) and six of the known /-kaurene type diterpenoids, kamebakaurinin, isodomedin, umbrosinA, mebadonin, kamebakaurin, and kamebanin were recognized. Kamebanin was found in all... 

From the kaurane-type diterpenoids, ent-kaurenic acid, Fig. (13) and ent-kaurenol, Fig. (14) were reported from the roots of Baccharis ramoisissima Gardn. [391, Baccharis minutiflora Mart. [451 and Baccharis intermixta Gardn. [25],... 

Interconversions among Rabdosia diterpenoids have been frequently undertaken to establish the structures of new compounds, but were occasionally carried out as a matter of purely chemical interest. The following discussion is limited to interconversions between kaurene-type and 6,7-secokaurene-type diterpenes. The transformations are divided into biogenetic-type and retrobiogenetic-type chemical conversions. 

Oxidation patterns of ring D in Rabdosia diterpenoids derived from ent-16-kaurene are classified into 5 types shown in Table VI. Each class exhibits characteristic spectral data, from which the structural features of ring D are easily deduced. Table VI shows typical UV, IR, and NMR data for a typical example belonging to each class. 

From Jungermannia infusca, e f-kauren-15-one (498), ( 6R)-ent-kauran-15-one (501) and /-15a-hydroxykaurene (504) have been obtained. Structures were confirmed by comparison of properties with those of substances previously known only as the result of chemical transformations and not as natural products (213). Later work on the diterpenoids of J. infusca resulted in the isolation of two previously known kaurane-type ketoalcohols (499, 502) and their acetates (500, 503) (246), the latter being new natural products. 

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