Synthesis of Porphyrin‐Anthraquinone Conjugates as Photosensitizing Agents

Abstract

A series of 5,10,15,20‐tetraarylporphyrins covalently linked to anthraquinones belonging to the class of emodin were synthesized following two different pathways. The first method exploits the functionalization of the methyl group in position 6 of O‐protected emodins, which can be converted either into a carboxylic acid or into a bromo‐methyl derivative. The modified emodins were then bound through amido or ether bonds to one of the tetraarylporphyrins meso phenyl rings bearing an amino or hydroxyl group, respectively. An alternative synthesis exploits the mixed condensation of triacetoxy‐emodinaldehyde (or trimethoxy‐emodinaldehyde) with pyrrole in the presence of variable amounts of benzaldehyde, thus affording two similar 5‐emodin‐10,15,20‐triphenylporphyrins differing from one another in the emodin hydroxyl group protection. These compounds are characterized by direct conjugation of the emodin moiety to the tetrapyrrolic ring. Preliminary experiments were performed in vitro on the human colon adenocarcinoma cell line HCT116 to evaluate the photocytotoxicity of the new compounds.

Keywords:

• Emodin
• HCT116
• hybrids
• porphyrin
• synthesis

Acknowledgment

Financial support by Indena S.p.a. for a postdoctoral fellowship (S. A.) is gratefully acknowledged.