A general, convenient method for the preparation of 1,7-and 1,9-disubstituted xanthine derivatives (paraxanthine and isoparaxanthine analogs) was developed starting from 6-amino-2methoxypyrimidin-4-one. Alkylation with alkyl halides in acetone/potassium carbonate in the presence of a phase-transfer catalyst (PTC) yielded an equimolar mixture of N3-and O 4 -alkylated products, which could be separated by dry column chromatography. The N3-alkylated uracil derivatives were converted to the corresponding 1-alkyl-2-methoxypurin-6-ones by standard procedures. PTC alkylation yielded an equimolar mixture of 7-and 9alkylated isomers, which were again conveniently separated by dry column chromatography. The title compounds were obtained after acid hydrolysis of the 2-methoxy group in satisfactory yields.

In order to exclude possible interferences in the many indirect superoxide dismutase (SOD) activity measurements using the copper-putrescine-pyridine complex (Cu-PuPy) a pulse radiolytic study on this diSchiff base copper complex has been devised and sucessfully performed. The reaction kinetics and rate constants of pulse radiolytically generated superoxide in the presence of Cu-PuPy reveal pseudo first-order characteristics. The rate constant (k 2 = 6 + 1 • l0 s ~1 -! s -t) is comparable to that of an Fe-SOD and is approximately a factor of 3 lower than that of bovine Cu2Zn2-SOD. The superoxide dismutating activity of Cu-PuPy shows a more pronounced temperature dependence compared with that of Cu2Zn2-SOD. Arrhenius analyses yielded activation energies of 7.8 +_0.3 and 4.6 +_ 0.2 kcalmo1-1 for Cu-PuPy and Cu2Zn2-SOD, respectively. The rate constant of the reaction of superoxide and Cu-PuPy is highest at pH 5.0. The possible application of Cu-PuPy for new therapeutic strategies on all types of inflammatory diseases appears to be promising.

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In the course of an oxidative burst oxygen free radicals and hypothiocyanite (OSCN-), a transiently abundant derivative of thiocyanate (SCN-), are formed in the presence of activated polymorphonuclear leukocytes (PMNs). At the same time Cu(I)-thionein is present and the question arose whether or not thiocyanate and its oxidized form may transiently release highly Fenton active copper to improve the efficacy of the above mentioned oxidative burst. Thus, the reaction of yeast Cu-thionein with OSCN- was examined. Indeed, a release of copper from the Cu(I)-thiolate clusters of the protein was observed ex vivo. Both the chiroptic and luminescence emission signals of Cu-thionein essentially levelled off in the presence of a 15-fold molar excess of OSCN- expressed per equivalent of thionein-copper. The effective copper-releasing activity of this reagent was confirmed by equilibrium dialysis. The demetallized protein could be reconstituted under reductive conditions. SCN- did not affect the copper-thiolate bonding. It rather acts as a potent metabolic source for the transient copper release from Cu-thionein in the presence of activated PMNs.