Concise Total Synthesis of Agarozizanol B via a Strained Photocascade Intermediate

The prezizane‐type sesquiterpene agarozizanol B was synthesized employing a photochemical cascade reaction as the key step. Starting from a readily available 1‐indanone with a tethered olefin, a strained tetracyclic skeleton was assembled which contained all carbon atoms of the sesquiterpene with the correct relative configuration. The conversion into the tricyclic prezizane skeleton was accomplished by a strategic cyclopropane bond cleavage. Prior to the cyclopropane ring opening an adaption of the oxidation state was required, which could be combined with a reductive resolution step. After removal of two functional groups, the natural product was obtained both in racemic form or, if resolved, as the (+)‐enantiomer which was shown to be identical to the natural product. Starting from a simple indanone derivative, diastereomerically pure intermediate 1 was formed in a photochemical cascade and served as precursor to agarozizanol B (2), either as racemate or as single enantiomer after a resolution step.