This cascade cyclization process is ideally suited for the total syntheses of sesquiterpenes (−)-4α,7α-aromadendranediol ( 92 ), (−)-4β,7α-aromadendranediol ( 93 ), and (−)-epiglobulol ( 94 ) from a single dienyne 84b by using a stereodivergent gold(I)-catalyzed reaction as the key step (Scheme 24 ). 115 In the absence of any external nucleophile, cyclopropyl gold(I) carbene intermediate 89 undergoes a 1,5-OBn migration followed by intramolecular cyclopropanation to form tricyclic compound 88b, which is the precursor of 93 and 94 .
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