Chemical Studies on Products Obtained from Verdohemochrome IXα Dimethyl Ester by Treatment with Ammonia under Air

Verdohemochrome IXα dimethyl ester [bis(pyridine)iron(II) 5-oxaprotoporphyrin IX dimethyl ester] gave 5-azaprotohemin IX dimethyl ester (2) and six tripyrrin derivatives upon treatment with ammonia under air, followed by methylation. The reaction of 2 with coned HCl in acetic acid in the presence of ferrous sulfate, followed by methylation gave demetallated product, 5-azaprotoporphyrin IX dimethyl ester (8), accompanied by products obtained by the hydration and reduction of both or one of the vinyl groups of 8. 8,12-Bis[2-(methoxycarbonyl)ethyl]-3,7,13-trimethyl-1-oxo-2-vinyltripyrrin-14-carbaldehyde, obtained as a major tripyrrin product by an oxidative degradation of 1, gave a pyrromethene derivative, 3,7-bis[2-(methoxycarbonyl)ethyl]-2,8-dimethyl-l-methoxy-5-pyrromethene-9-carbaldehyde by the reaction with Tl(OAc)3 under air. The structures of all products obtained in the present study were determined by spectral measurements.