Ethyl 4-formylpyrrole-2-carboxylates were prepared from nitroacetaldehyde dimethyl acetal in 9–50% yields using the Barton–Zard reaction. These formylpyrroles were successfully transformed to cycloalkano-oligopyrroles. The conformation of cyclononatripyrroles in CDCl 3 was found to be a crown form based on the NMR analysis, while cyclododecatetrapyrroles were in two interconverting boat and chair conformations.
[Peterson, Mark L.; Corey, Susan D.; Font, Jose L.; Walker, Mark C.; Sikorski, James A. Bioorganic and Medicinal Chemistry Letters, 1996 , vol. 6, # 23 p. 2853 - 2858]
