Acidified nitrite mixtures react with octaethylporphyrin, mesoporphyrin dimethyl ester, and (less effectively) octaethylhaemin to give rneso-nitro-derivatives. Such products are also furnished by the reaction of sodium nitrite or nitric oxide with a preparation of the radical cation of zinc(ir) octaethylporphyrin. The radical cation also gives meso-substituted derivatives with chloride, thiocyanate, and benzoate ions.Nitrosylhaems are characterised from the reactions of nitric oxide with octaethylhaemin and protohaemin dimethyl ester. The pigment of cured meat, nitrosylprotohaem, has been fully characterised (as its dimethyl ester) for the first time. The reaction of excess of acidified nitrite with octaethylhaemin for a short period gives a product regarded as a mixture of mono-and di-nitrosyl derivatives, but in the presence of ascorbic acid nitrosyloctaethylhaem is formed cleanly. Under suitable conditions nitrosyihaems react with secondary amines to generate nitrosamines. The results are discussed in the context of the chemistry of meat curing processes.
112, 67;
Rubenine, a carboxy-indole alkaloid derived from tetrahydrodeoxycordifoline (6) with a unique N(b)-C-18 linkage, has been isolated from Adina rubescens and its structure established as (la).
A comparison of the photosensitizing ability of a variety of porphyrins for photohaemolysis gives the following order of activity: protoporphyrin greater than deuteroporphyrin, mesoporphyrin, haematoporphyrin dimethyl ester much greater than haematoporphyrin diacetate, haematoporphyrin greater than haematoporphyrin monoacetate, coproporphyrin III, haematoporphyrin derivative, coproporphyrin III tetramethyl ester greater than uroporphyrin I, meso-tetra-(N-methyl-4-pyridinium)porphyrin tetratoluene-p-sulphonate, meso-tetra-(p-carboxyphenyl)porphyrin, protoporphyrin dimethyl ester, meso-tetra-(p-hydroxy-sulphonylphenyl)porphyrin tetrasodium salt, uroporphyrin III, deuteroporphyrin-3,8-disulphonic acid and protohaemin. The results for the metal-free porphyrins are rationalized in terms of solubility and partition properties, and a model is proposed for the incorporation of amphipathic porphyrins into the membrane lipid bilayer. Experiments with erythrocytes from patients with erythropoeitic protoporphyria and with normal erythrocytes to which porphyrin was added in a deuterium oxide medium do not lead to an increase in the rate of photohaemolysis. A possible explanation for this somewhat surprising observation is outlined.
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