Novel Chlorins with a δ‐Lactone Ring Fused at Ring D.

Abstract Reaction of purpurins ( 1a,b ) with DDQ resulted in oxidative ring closure at ring D to give novel δ-lactones ( 2a,b ), mild treatment of which with TFA/methanol gave chlorins ( 3a,b ) possessing a hydroxy group at C-18. Prolonged treatment of ( 3a,b ) with TFA resulted in their dehydration and the formation of porphyrins ( 4a,b ). © 1997 Elsevier Science Ltd.