A General Synthesis of Pyrroles and Fused Pyrrole Systems from Ketones and Amino Acids

The lithium enolates of ketones react with BOC-α-amino aldehydes and BOC-α-amino ketones to afford aldol intermediates that cyclize under acidic conditions to yield pyrroles. The BOC-amino aldehydes and ketones are readily available from α-amino acids. The method allows incorporation of a wide variety of substituents at any of the five atoms of the pyrrole ring and is also suitable for the preparation of fused pyrrole systems.