Stereochemical studies on porphyrin a: assignment of the absolute configuration of a model porphyrin by degradation

Abstract

The synthesis is described of a porphyrin alcohol (22) which has a structure very similar to that of porphyrin a(2). The model porphyrin was resolved by separation of its camphanate esters. Ozonolysis of the 2-nitrobenzoate of each enantiomer in tritiated form gave a derivative of 2-hydroxypentanedioic acid whose configuration was determined by dilution analysis. It is demonstrated that correlation of the stereochemistry of porphyrin a with that of the model (22) will be possible by means of the ¹H and ¹⁹F n.m.r. spectra of the corresponding esters with (–)-3,3,3-trifluoro-2-methoxy-2-phenylpropanoic acid.