The synthesis of a number of 3,4-fused cycloalkanopyrroles bearing substituents on the cycloalkane ring was accomplished by 1,3-dipolar cycloaddition. The yield of the cyclization appeared to depend on the base-sensitivity of the Michael acceptor, but the method is applicable across a broad range of cyclic ?,?-unsaturated ketone esters. Functional group transformations can be undertaken following pyrrole synthesis to increase the diversity of cycloalkanopyrroles accessible by this method. One pyrrole thus made is an diester of a conformational constrained analogue of porphobilinogen, the precursor of the natural tetrapyrroles.
Department of Chemistry
University of Cambridge