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Szmzmary A new, general, stepwise porphyrin synthesis in which tripyrrenes (2) and 1 ', 8'-dimethyl-a,c-biladienes (9) are crystalline and fully characterised intermediates is exemplified in the first total synthesis of isocoproporphyrin tetramethyl ester (1).

Syntheses of 7‐(3‐ethoxycarbonylpropyl)‐2,3,5‐triethyl‐1,4,6,8‐tetramethylporphyrin (8) (via the MacDonald dipyrrylmethane route) and 2‐(2‐chloroethyl)‐4‐ethyl‐6‐methoxycarbonyl‐7‐(3‐methoxy‐carbonylpropyl)‐1,3,5,8‐tetramethylporphyrin (22) (via the tripyrrene route) are described. The corresponding pyrrolidides of these compounds were cyclized in high yield to furnish the spiro imines (20 and 30 respectively), but attempts to hydrolyze these imines to the appropriate spiroketochlorins were largely unsuccessful. A small amount of the spiroketochlorin 9 (from 8) was obtained, and this was successfully hydrogenated to give the dihydro derivative 21. The major problem in imine hydrolysis was observed to be reversion to the parent porphyrin through simple bond migration and spiro ring cleavage. A successful transformation of protoporphyrin‐IX dimethyl ester (31) into mesoporphyrin‐IX dimethyl ester (32) using di‐imide generated from dipotassium azodicarboxylate is described.

Die Pyrrole (I) und (II) kondensieren in Essigsäure in Gegenwart von p‐Toluolsulfonsäure als Katalysator zu dem Pyrromethan (IIIa), das durch Hydrierung über Palladiumkohle zur Carbonsäure (IIIb) debenzyliert wird.