Biosynthesis of the natural porphyrins: experiments on the ring-closure steps and with the hydroxy-analogue of porphobilinogen

Experiments on the conversion of porphobilinogen PBG (1) into uro'gens support formation of the pyrrolenine (4) which, at least for production of uro'gen-I (9), is converted next into the hydroxymethylbilane (6); the status of the latter for uro'gen-III (10) formation and the nature of the interaction between deaminase and cosynthetase are also studied.