Himachalanes, Longifolanes and Longipinanes

Along with longifolane- and longipinane-types sesquiterpenes, (-h)-a-himachalene (436), (—)-P-himachalene (437) and (-h)-y-himachalene (438) have been isolated from Scapania undulata (2, 223). All himachalanes isolated are antipodal to those obtained from higher plants. 

Huneck and Klein (160) reported isolation and characterization of the essential oil obtained from seven Jungermanniales species and one Metzgeriales species. From Scapania undulata, (—)-longifolene (439) and (—)-longiborneol (443) were isolated and their structures established by comparison of their spectral data with those of authentic samples. This represented first isolation of terpenoids from the Hepaticae and of sesquiterpenoids antipodal to those found in higher plants. The presence of longifolene (439) and isolongifolene (440) in Scapania species was revealed by GC-MS analysis (314). 

Chart 20. Himachalanes, longifolanes, longipinanes, and sativanes found in the Hepaticae 

The relative stereochemistry of (449) was established by studying the H-NMR spectrum in the presence of shift reagents which revealed large and nearly equal shifts for the two bridgehead protons. The conformational preference of the cyclohexane ring for the half-chair was based on the facile dehydration and detailed analysis of H-NMR spectrum (2). 

The structure of acetoxymarsupellone (447) was elucidated by comparison of the H-NMR and C-NMR spectra with those of the cometabolites (446, 448). The absolute stereochemistry of the longipinanes found in the Hepaticae are antipodal to those found in higher plants. 

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