Porphyrin formation

The bromo substituent in l-bromo-19-meLhyl-l,l9-dideoxybiladienes- c is not essential for porphyrin formation. When 1-methylbiladiene-ac dihydrobromide or the 1,19-dimethyl-biladienc-ac are heated in refluxing methanol or dimethylformamide in the presence of cop-per(II) salts, the porphyrin copper complexes 13 are formed by oxidative cyclization. The free porphyrins can then be obtained by removal of the copper with acid. A wide range of porphyrins 13 can be prepared by this method. However, a restriction is the accessibility of the starting material with special substitution patterns. 

This strategy is not applicable for pentaphyrin, since the condensation reaction of a, -free oligopyrrole and a,a -diformyldipyrrole invariably results in porphyrin formation.276 The disproportionation problem can be avoided by using an a,a -diformyltripyrrole (52) and an a.a -free dipyrrole (53) (Scheme 107).277... 

Interfacial Metal Ion Complexatlon. Complexatlon of copper (II) ion by oil soluble ligands has been implicated in metallo-porphyrin formation in benzene in water MB s, but not apparently in the mineral oil in water system (vide supra). Therefore, an electrochemical study of the interaction of quinoline and copper ion was undertaken. 

Protection against sunlight and prevention of skin infections are essential. Sunscreen ointments may occasionally provide some benefit, but physical avoidance of UVA radiation is usually necessary. Hypertransfusion and activated charcoal to decrease the enterohepatic circulation of porphyrin, hydroxyurea, intravenous heme, and antioxidant preparations have also been used to suppress erythropoiesis and porphyrin formation or to ameliorate the effects of porphyrin accumulation but none has been shown to have a reliable, long-term effect. Hemolytic anemia may require repeated transfusion and infusion of deferoxamine to prevent iron overload. 

Lange, M. and D. Mansuy (1981). N-Substituted porphyrin formation from carbene iron-porphyrin complexes A possible pathway for cytochrome P-450 heme destruction. Tetrahedron Lett. 22, 2561-2564. 

Porphyrin formation from 13 occurs as the result of a repeated cationic domino process [23]. This also applies to the biosynthesis of haemin, chlorophyll and vitamin B12 from 5-amino-4-oxobutanoic acid via porphobilinogen (13 R = CH2CO2H, R =CH2CH2C02H, NH2 in place of NMe2) [24]. 

C. Fritsch, W. Stahl, K.W. Schulte, H. Sies, G. Goerz, P. Lehmann, T. Ruzicka (1998). Optimum porphyrin formation in skin tumors and psoriatic lesions after topical application of (5-aminolevulinic acid. J. Invest. Dermatol., 110, 673(A). 

D.M. Guldi, P. Hambright, D. Lexa, P. Neta, and J.-M. Saveant, One-Electron Reduction of Chromium(III) Porphyrins. Formation of Chromium(II) Porphyrins or Chromium(III) Porphyrin 7r-Radical Anions, J. Phys. Chem., 86 (1992) 4459. 

N-acetylated derivatives leads to the formation of Fe(II) porphyrins together with the acyloxy radical which undergoes decarboxylation to give ammonio-alkyl or amidoalkyl radicals. Large differences in the observed rates of Fe(II) porphyrin formation can be accounted for in terms of two factors, the binding affinity of the carboxyl to form a photoactive complex, and competitive reactions of acyloxy radicals following photolysis. 

G. Bringmarm and B. Franck, Tetrapyrrole biosynthesis 14 Extremely selective porphyrin formation by cyclisation of different oligopynoles," Liebigs Ann. Chem. 1272 (1982). 

Ultimately, all porphyrin syntheses start from pyrroles (which themselves need to be made), so that a special section with this title might appear pointless. However, this section really deals with those porphyrins where the number of chemical manipulations that the pyrrole has to go through prior to porphyrin formation, is minimal the porphyrin is synthesised directly from the final pyrrole. This means that such synthetic routes are usually confined to those porphyrins with a symmetrical arrangement of peripheral substituents, e.g., 5,10,15,20-meso-tetrakis(aryl)porph)rrin (e.g. TPP) and 2,3,7,8,12,13,17,18-octa-substituted porphyrins (e.g. OEP). 

Metal Porphyrin Formation.— The rate of formation of cationic porphyrin complexes of copper(ii) is dependent on the basicity of the ligand. Tetra-(4-A, iV, iV"-trimethylanilinium)porphyrin, H2TAP, reacts with a second-order rate constant of 6.2 s, almost thirty times faster than the corresponding... 

Efforts towards the preparation of porphyrin-functionalized polythiophenes have centered on complexes 38-41, in which thiophenes are tethered to porphyrin cores (Chart 5.9) [50], The syntheses employed either porphyrin formation using MacDonald-type conditions (38-40) or Wittig coupling to produce 41. No electronic properties of these materials have yet been reported. 

Lukton D, Mackie JE, Lee JS, Marks GS, Ortiz de Montellano PR (1988) 2,2-Dialkyl-l,2-dihydro-quinolines cytochrome P-450 catalyzed N-alkyl-porphyrin formation, ferrochelatase inhibition, and induction of 5-aminolevulinic acid synthase activity. Chem Res Toxicol 1 208-215... 

Lange M, Mansuy D (1981) N-substituted porphyrins formation from carbene iron-porphyrin complexes a possible pathway for cytochrome P450 heme destruction. Tet Lett 22 2561-2564... 

Studies of porphyrin production in rats treated with DDC by gastric tube (300 mg/kg) revealed a decrease in liver ATP of 50% within 2 hours, while porphyrins increased continuously between 2 and 6 hours. On the other hand, intravenous administration of high doses of ATP was found to decrease the porphyria [Gajdos and Gajdos-Torok, 4]. Studies on chick embryo liver cells suggested that the decrease in porphyrin formation may not have been due to a lowering of ALA-synthetase activity but rather to an effect on some intermediate steps of heme biosynthesis [128]. When ATP, NADPH, ascorbate, orpiperonyl butoxide was added to the culture medium, porphyrin formation was diminished but ALA-synthetase activity was not appreciably affected. 

Organoohemical Methods of Porphyrin Formation of Biological Interest 301... 

Early observation of the Fe(IV) porphyrin formation by the electrochemical oxidation was confirmed by Bruice et al and Groves et al. by employing monomeric Fe (TMP)OH as the starting species [115-117]. Kadish added Fe (TMP)OR as a precursor of Fe(IV) species [118]. In addition, Bruice also provided spectroscopic evidence for the formation of Fe (TMP) 7C-cation radical as a two-electron oxidation product [115]. 

Tabata, M. and H. Morita. 1997. Spectrophotometric determination of a nanomolar amount of ascorbic acid using its catalytic effect on copper(II) porphyrin formation. Talanta 44 151-157. 

This reaction is complicated and has many steps. The simpler condensation of one molecule of benzaldehyde and two of pyrrole to give the product shown below, a dipyrrylmethane, is illustrative of the first stage in porphyrin formation. Propose a step-by-step mechanism for this process. 

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