Opening of forbinexocycle by weak O-nucleophiles. Study and optimisation of free chlorine e6 synthesis methods

The article considers issues concerning the reaction of exocycle opening in phorbin molecules (on the example of methylpheophorbide a) under the O nucleophiles - water and alcohols action. According to the author, under certain conditions relatively weak nucleophiles as water and alcohols can cause the opening of the exocycle in the molecule of methylpheophorbide a with the formation of chlorine derivatives e6. The study of this reaction, in addition, reveals new synthetic methods to obtain chlorine e6 esters of different degrees of substitution, and eventually - free chlorine e6 in the form of triacids. Free chlorine is a valuable photosensitiser for photodynamic therapy (PDT), and a starting compound for the preparation of other photosensitizers. The article also discusses possible synthetic approaches to obtain free chlorine e6.