Bacteriopurpurins: Synthesis from meso-Diacrylate Substituted Porphyrins

A new route to the synthesis of bacteriopurpurins from symmetrical and unsymmetrical meso-substituted diacrylate octaalkylporphyrins has been achieved using basic conditions. Reaction of 5,15-bis[β-(ethoxycarbonyl)vinyl]octaethylporphyrin or 5,15-bis[β-(ethoxycarbonyl)vinyl]etioporphyrin I, in toluene in the presence of DBU, produces the corresponding bacteriopurpurins, without formation of the corresponding iso-bacteriopurpurins. Bacteriopurpurin formation from the cyclization of the 5,10-bis[β-(ethoxycarbonyl)vinyl]porphyrins were found to be dependent on the initial cyclization process and the structure of the meso-acrylate purpurin formed. In the etioporphyrin series the cyclization process was shown to be highly specific, favoring cyclization of the acrylate groups toward a specific ethyl group on the porphyrin ring.