BIOSYNTHESIS OF PORPHYRINS AND RELATED MACROCYCLES .7. SYNTHESIS OF SPECIFICALLY LABELED [1)UROPORPHYRIN-III-C-14] AND OF [10,14-C-13(2)]-UROPORPHYRIN-III - CONVERSION OF LATTER INTO [10,14-C-13(2)]PROTOPORPHYRIN-IX - BIOSYNTHETIC SIGNIFICANCE OF ITS C-13 NUCLEAR MAGNETIC-RESONANCE SPECTRUM

Uroporphyrin-III was synthesized by a route which allows [2,11-13C2]porphobilinogen to be elaborated to give [10,14-13C2]uroporphyrin-III. This, after reduction to the corresponding porphyrinogen was transformed enzymically into [10,14-13C2]protoporphyrin-IX. The 13C NMR signal from postion 10 (.beta.-meso-carbon) of the methyl esters of both porphyrins appears as a 5.5 Hz doublet. This demonstration of long-range coupling is of decisive importance for related research on the nature of the rearrangement process by which the natural type III porphyrins are biosynthesized. A new procedure was developed for pyrromethane formation, based on catalysis by tin(IV) chloride, which appears to be of general value.