Hematoporphyrin and Protoporphyrin Analogues

It is believed that part of the chemical complexity of Photofrin is due to the instability of the benzylic secondary hydroxy group towards the strong reaction conditions used in its manufacturing process. - Thus, a large number of hematoporphyrin analogues have been synthesized by several research groups by introducing a variety of substituents at different positions of the macrocycle. -  

Hill et al. were the first to report an interesting approach to combine PDT with boron neutron capture therapy (BNCT) and later studied the selective tumor uptake of a boronated protoporphyrin 6 in mice bearing an implanted intracerebral glioma. TTiey found this compound to be selectively localized in tumor at ratios as high as 400 1 relative to normal brain, indicating that this compound may be used as a potential drug for PDT and boron neutron capture therapy (BNCT). Another approach to overcoming the problem of HpD s chemically complex nature was the use of pure porphyrins such as isohematoporphyrin 7 and 

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