Chaperon, A.; Bertschy, H.; Franz-Schrumpf, A.-L.; Hugelet, B.; Neels, A.; Stoeckli-Evans, H.; Neier, R. The Synthesis of a Pyrazol Analogon of Porphobilinogen With the Help of the Mukaiyama Aldol Reaction. Chimia 2003, 57, 601.