Synthesis of an optically active dipyrrinone sulfide and sulfoxide

Optically active dipyrrinone sulfide 2 and its sulfoxide 1 have been synthe sized as potential precursors to tetrapyrrole analogs of bilirubin with sul foxide groups replacing the natural carboxylic acids. Dipyrrinones 1 and 2 show weak exciton coupling in their circular dichroism spectra, with Delta epsilon(427)(max) -0.44, Delta epsilon(398)(max) +0.50 from 1, and Delta ep silon(442)(max) -0.67, Delta epsilon(404)(max) +1.20 from 2, but no evidenc e for inter- or intramolecular hydrogen bonding between the dipyrrinone NHs and the sulfoxide group of 1. (C) 1999 Elsevier Science Ltd. All rights re served.