| Sumario: | The total synthesis of meso-monoaryl protoporphyrins (1) and (2) using a MacDonald type [2+2] condensation is described. In this method a bisformyl dipyrrylmethane is treated with a biscarboxydipyrrylmethane. Attempts to obtain the δ-meso-monoaryl protoporphyrin (7) by the a,c-biladiene method failed as it could not be prepared starting from its tripyrrene precursor. The synthesis of the latter compound is described. Molecular modeling studies allowed us to find the most favorable conformations for compounds (1) and (2). In both porphyrins, the exocyclic phenyl group adopts a noncoplanar disposition relative to the plane of the macrocycle. In porphyrin (2) the macrocycle is nearly planar while nonplanar saddle conformation was obtained for porphyrin (1).
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