Earl W. Baker

The preparation of mesoporphyrin IX and etioporphyrin III

Abstract Under mild alkaline conditions hemin can be catalytically hydrogenated to the iron complex of mesoporphyrin IX. Subsequent demetallation yields mesoporphyrin IX. In this way pure mesoporphyrin IX becomes readily accessible. In contrast, the mesoporphyrin produced from hemin by formic acid reduction has been shown by partition chromatography to be a mixture rather than a pure compound. Mesoporphyrin IX can be converted to pure etioporphyrin III in 20% yield by a seven-step reaction series including the Curtius rearrangement, Hofmann degradation, and catalytic hydrogenation.

Substituent effects in porphyrins and metalloporphyrins

Abstract Substituent effects on complex formation between variously substituted metallodeuteroporphyrins with filled t 20 orbitals and extraplanar ligand(s) can be correlated by Hammett free-energy plots. The slopes of these plots are positive and the correlation is high with substituent constants typical of resonance transmission of electronic effects. Conversely, correlation of the monoprotonation of substituted deuteroporphyrins requires σ m substituent constants, indicative of the inductive mode of transmission. Electron spin resonance spectra of the d 9 metalloporphyrins are in accord with the concept of the resonance mode of transmission and suggest that the porphyrins with strongly electron withdrawing groups produce a relatively low ligand field.

COLUMN PARTITION CHROMATOGRAPHY OF PORPHYRINS.

Abstract A number of porphyrins can be resolved by column partition chromatography using dimethyl sulfoxide on a silica support and cyclohexane as the mobile phase. This partition system was used as a criterion of success in the selection of new methods for the synthesis of porphyrins. The important factors which allow quantitative and reproducible evaluations of Rf values are noted, and differences in dielectric constant are recommended as a useful test for selection of other suitable chromatographic solvent pairs.