ABSTRACT
The subject has already been introduced in a descriptive way in section 1.2.4. Haematoporphyrin (2) has two secondary benzylic-type alcohol functions at C-31 and C-81. Diastereoisomerism arises as a result of these two positions; and because of their benzylic reactivity it is one of the most difficult of the naturally-derived
2 Haematoporphyrin (P = -CH2CH 2CO2H)
porphyrins to get pure. (Schwartz found that various commercial samples contained up to 15 components). Haematoporphyrin is readily available in crude form from slaughterhouse blood (or from haemoglobin from that source). Treatment with mineral acid (H2SO4 or HBr-HOAc) followed by hydrolytic work-up removes the protein and the iron to generate haematoporphyrin (generally isolated as its dihydrochloride) in one operation. The procedure was first described by Scherer in 1841: although he did not characterise the product, he did show that it was ironfree, and was thus the first to demonstrate that the red colour of haemoglobin was not primarily due to the iron which it contained. Haematoporphyrin was first properly described in 1867 by Thudichum (who called it “cruentine”): however, the name which has stuck, and which has led to the series name (Greek: porphuros = purple) was provided by Hoppe-Seyler in 1871.
