Synthesis of the Dolabellane Diterpene Hydrocarbon (±)‐δ‐araneosene

Abstract The racemic form of the bicyclic diterpene hydrocarbon δ‐araneosene ( 4 ), endowed with the dolabellane skeleton, was prepared from geraniol in two different ways. The more efficient route involved 13 steps and proceeded with an overall yield of 3.6% (average: 77% per step). With this reference sample at hand, the hitherto elusive metabolite (−)‐ 4 , a likely biogenetic precursor of cycloaraneosene ((−)‐ 3 ) and sordaricin ((−)‐ 1 ), could finally be isolated in ≥ 99.5% purity from the neutral fractions of the mold Sordaria araneosa C AIN (Ascomycetes).