Über Phäoporphyrine

Chlorophyll.

“…As this might occur in three ways, theory predicts twenty-four isomeric pyrroporphyrins and the same number of rhodoporphyrins, since it was highly probable, through the transition from rhodoporphyrin to pyrroporphyrin with splitting off of carbon dioxide, that in place of the free methine group in pyrroporphyrin a nuclear carboxyl group was present in rhodoporphyrin. The synthesis of certain pyrro-and rhodo-porphyrins completely confirmed this assumption (46,6,5,47).…”

“…Cautious reduction with hydriodic acid and glacial acetic acid proved fruitful in results here; application of this method to pheophorbide and to chlorin e yielded fundamentally different results. The pheophorbides gave pheoporphyrins; chlorin e gave chloroporphyrins (3,4,31,32,33,34,10). Spectroscopically, essential differences between the two classes were manifest.…”

Recent Progress in Determining the Chemical Structure of Chlorophyll.

“…Fischer found a mild reagent for the degradation of chlorophyll in glacial acetic acid solutions of hydrogen iodide at 50°C. By such treatment, many chlorophyll derivatives are reduced to colourless leuco compounds, which re-oxidize in air to porphyrins (47,18,65,48); these, however, unlike the chlorophyll porphyrins previously described, retain the full carbon skeleton of the original compound. In this manner the pheophorbides give rise to pheoporphyrins, while chlorin e gives rise to a different series, the chloroporphyrins.…”

“…The chlorins also differ in chemical activity. Chlorin p6 and its dihydro compound revert spontaneously to pheopurpurin 18 and its dihydro compound, respectively, while pseudochlorin p6 only gives pheopurpurin 18 on heating, and the dihydro compound is completely stable. Fischer's explanation is that the carboxyl groups in the normal series are adjacent to each other, and thus anhydride formation is possible (formulas XXX).…”

Propentdyopents [5-(2-oxo-2H-pyrrol-5-ylmethylene)pyrrol-2(5H)-ones] and related compounds. Part 1. On the structure of the propentdyopent–alkanol adducts

“…(ii) at the meso-bridge [bin (15)] to give the meso-derivative (17) or tautomer; and (iii) at the valley position [c in (IS)] to give the adduct (18) or a tautomer. and (18) proved to be more difficult. However the available evidence clearly favoured (18).…”