Facile Synthesis and First Antifungal Exploration of Tetracyclic Meroterpenoids: (+)-Aureol, (−)-Pelorol, and Its Analogs

As an important bioactive molecular backbone, drimane meroterpenoids have drawn a great deal of attention from both pharmacologists and chemists. Inspired by the prevalidated success of conformational restriction in the discovery of novel pharmaceutical leads, two distinct tetracyclic drimane meroterpenoids, (−)-pelorol and (+)-aureol, were synthesized from the inexpensive starting material (−)-sclareol through 10 and 8 steps with 5.6% and 5.4% overall yield, respectively. The mild conditions, operational facility, and scalability enabled the expedient synthesis and biological exploration of not only natural products themselves but also their mimics. The first agrochemical exploration showed (−)-pelorol and (+)-aureol possessed good antifungal activity against Rhizoctonia solani, with EC₅₀ values of 7.7 and 6.9 μM, respectively. This revealed that tetracyclic drimane meroterpenoids are valuable models for antifungal lead discovery.