Compositions and methods of making a photoactive agent

A process for preparing a chlorin e6 anhydride, or a pharmaceutically acceptable salt thereof, the process comprising:

• combining chlorin e6 with a carboxyl activating agent to obtain a mixture comprising a chlorin e6 anhydride having the following formula:
• or a pharmaceutically acceptable salt thereof;
• and
• purifying the chlorin e6 anhydride or pharmaceutically acceptable salt thereof.

A method for preparing mono-L aspartyl chlorin e6, or a pharmaceutically acceptable salt thereof, the method comprising:

• combining a Formula I intermediate:
• with an aspartate salt composition having a pH ranging from about 10 to about 12 in the presence of an organic solvent to form a reaction mixture;
• making the reaction mixture basic;
• and
• precipitating the mono-L aspartyl chlorin e6, or a pharmaceutically acceptable salt thereof, from the basic reaction mixture.

A process for preparing a mono-amino acid chlorin e6, or a pharmaceutically acceptable salt thereof, comprising:

• combining chlorin e6 with a carboxyl activating agent to obtain a mixture comprising a Formula I intermediate
• or a salt thereof;
• isolating the Formula I intermediate, or salt thereof;
• and
• combining the isolated Formula I intermediate, or salt thereof, with an amino acid-containing reagent, or ester or derivative thereof, to form the mono amino acid chlorin e6, or a pharmaceutically acceptable salt thereof.