Aromadendranes and 2,3-Secoaromadendranes

Aromadendrane-type sesquiterpenoids are mainly distributed in Mylia, Plagiochila and Porella species belonging to the Jungermanniales. 2,3-Secoaromadendrane-type sesquiterpenoids have been isolated only from the Plagiochilaceae. A Mylia species contains a unique 1,10-secoaromadendrane-type sesquiterpene. 

Tridensenone (40), whose structure assignment was based on spectral data, is the major component of Bazzania tridens 334). Myliol (44), a tetracyclic sesquiterpene alcohol, was isolated from Mylia taylorii 83, 88, 89) the structure proposal was based on careful analysis of the H-NMR and C-NMR spectra 6, 83, 88, 89). Because UV absorptions at 220 nm (log s, 3.70) and 275 280 nm (2.43 — 2.44) in (44) were difficult to reconcile with the proposed structure, structure (44) was established by X-ray crystallographic analysis of the / -bromobenzoate (82) 239, 275). 

The absolute configuration of (61) was established by further chemical degradation. Ozonolysis of (61) produced a ketoacid (69), followed by methylation to give a methyl ester (70), C11H18O4, [a]o —25.1 , whose spectral data were identical with those of (+)-c/.y-l-methoxycarbonyl-2,2-dimethyl-3-(3-oxo-n-butyl) cyclopropane, prepared by degradation of (+)-car-2-ene (71) and (-l-)-bicyclogermacrene (228). Thus, the structure and 

1) O3 2) CH2N2 3) PhCOjH/CHCla 4) KOH/MeOH 5) PCC 6) Ph3P = CHCOMe/CHClj 7) Hj/PtOa/EtOH 8) NaBH4 9) (MeO), P Oj 

NMR spectra in the presence of Eu(FOD)3 shift reagent. Oxidation of the isomeric dihydromyliols by Sarett s reagent gave dihydromylione A (43) and dihydromylione B (83). The spectral data of natural dihydromylione were identical with those of dihydromylione A. Acid treatment of myliol (44) also yielded dihydromylione A (43). 

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