Guaianes and Pseudoguaianes

Iso-oc-gurjunene B (418), an isomerization product of a-gurjunene (33) (720), is the major sesquiterpene hydrocarbon of the essential oil of Pellia epiphylla (96, 309). a- and P-guaienes (415, 416) were detected in Pellia endiviifolia and Plagiochila species by GC-MS (26, 47). 

Two new guaianolides, 8a-acetoxyzaluzanin C (426) and 8a-acetoxy-zaluzanin D (427) have been isolated from the female thallus of Conocephalum conicum and sterile thallus of Wiesnerella denudata, together with the previously known zaluzanin C (424) and zaluzanin D (425) (25,40). 

Various guaianolides occur in higher plants, particularly in Compositae. This is the first isolation of guaianolides from the lower terrestrial plants. 

Epoxidation of (428) gave a monoepoxide, whose spectral and chromatographic properties were identical with those of the naturally occurring 3a,4P-epoxyporelladiolide (429). The stereochemistry of the epoxide was established by the coupling constant associated with H-3 (J=2) in the H-NMR spectrum. 

Desacetoxydehydromatricarin (422) and desacetoxymatricarin (423) have been detected in Frullania vethii (45). 

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The same kind of rearrangement has been utilized in an intramolecular sense to transform the much more readily available decalin system into the bicyclo[5.3.0]decanes of the guaiane and pseudoguaiane sesquiterpenes. Thus, the Heathcock group synthesized confertin, as shown in Scheme 46 [82]. 

New additions to the guaiane family include sclerosporin (609), sclerosporal (610), sclerosporene (611), the guaienes (612) and (613) [which co-occurs with precatabrone (614)], and the guaioxide (615). The unusual pseudoguaiane caespitenone (616) has been isolated from the liverwort Porella caespitans This compound co-occurs with (-i-)-aristolone (617) and (-)-a-eudesmol (618), which are enantiomeric to those found in higher plants. 

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