Recent reports from this laboratory have been concerned with the electrochemical electron transfer reactions of biologically important, or potentially important, thiopurines 1-5. Because of the possibility of developing electrochemical syntheses and the potential of interpreting some of the generally incompletely understood biological transformations, based upon these fundamental electrochemical studies as well as their inherent analytical utility, examination of other thiopurine systems is continuing.
Reported here is the mechanism of the electrochemical reduction of 2-thiopurine at both the dropping mercury electrode (DME) and the pyrolytic graphite electrode (PGE), and the electrochemical oxidation at PGE. There appears to have been no previous studies into the electrochemistry of 2-thiopurine, and in fact little work has been reported on the biological activity. However, da Silva and Camargo 6 indicate that 2-thiopurine may be moderately effective for treatment of mice infected with Toxoplasma 9ondii.
EXPERIMENTAL
Chemicals
2-Thiopurine was obtained from K and K Laboratories. Buffer solutions were prepared from analytical reagent grade chemicals. Argon (Linde) used for deoxygenating purposes was equilibrated with water; no other purification was necessary.
Apparatus
Apparatus for polarography, voltammetry, cyclic voltammetry, coulometry and macroscale electrolysis and spectral data acquisition are described elsewheret -5.
RESULTS AND DISCUSSION
Electrochemical reduction
Polaroyraphy at DME. 2-Thiopurine exhibits three polarographic waves between pH 1 and 9. The most positive of these waves (wave I) occurs between pH 1 and 9. At pH 1 wave II appears at a more negative potential than wave I; it disappears above about pH 4.7. The third wave (wave III) appears between about pH 5 and 9