合成路线1

Michael addition of acrylonitrile to the enamine resultant from cyclohexanone (I) and pyrrolidine, followed by alkylation with ethyl bromoacetate, leads to the cyano ester (II). Subsequent Wittig reaction of (II) with methoxymethylene triphenylphosphorane affords the enol ether (III). The ester group of (III) is then reduced to alcohol (IV) using L-selectride. Further intramolecular cyclization of (IV) under acidic conditions gives rise to the bicyclic compound (V). Lithiation of p-bromostyrene (VI) with tert-butyllithium, followed by addition to nitrile (V) produces the ketone adduct (VII). Photooxygenation of (VII), followed by cyclization in the presence of trimethylsilyl triflate, furnishes the fused trioxane derivative (VIII). Finally, oxidative cleavage of the vinyl group of (VIII) with potassium permanganate yields the target carboxylic acid.