Photocyclization Reactions of Cyclohexa- and Cyclopenta-Fused Pyridinium Salts. Factors Governing Regioselectivity

The results of studies described in this report show that irradiation of 1,2-cyclopenta-fused
pyridinium perchlorate in aqueous base promotes a remarkably regioselective photocyclization
reaction that results in exclusive formation of a single tricyclic allylic alcohol. Moreover,
transformation of this photoproduct to a spirocyclic amido diester followed by enzymatic desymmetrization produces an enantiomerically pure monoalcohol. This chemistry comprises a highly
concise sequence for the preparation of what should become a useful synthon in synthetic organic
chemistry.