| | 1 | Author
| Agnieszka Bzowska3, Lucyna Magnowska3, Zygmunt Kazimierczukb | Requires cookie* | | | Title
| Synthesis of 6-Aryloxy-and 6-Arylalkoxy-2-chloropurines and Their Interactions with Purine Nucleoside Phosphorylase from Escherichia coli  | | | | Abstract
| The phase transfer method was applied to perform the nucleophilic substitution of 2,6-dichloropurines by modified arylalkyl alcohol or phenols. Since under these conditions only the 6-halogen is exchanged, this method gives 2-chloro-6-aryloxy-and 2-chloro-6-arylalkoxy-purines. 2-Chloro-6-benzylthiopurine was synthesized by alkylation of 2-chloro-6-thiopurine with benzyl bromide. The stereoisom ers of 2-chloro-6-(l-phenyl-l-ethoxy)purine were ob tained from R-and 5-enantiomers of sec.-phenylethylalcohol and 2,6-dichloropurine. A ll derivatives were tested for inhibition with purified hexameric E. coli purine nucleoside phosphorylase (PNP). For analogues showing IC50 < 10 ^.m, the type o f inhibition and inhibi tion constants were determined. In all cases the experimental data were best described by the mixed-type inhibition model and the uncompetitive inhibition constant, Kiu, was found to be several-fold lower than the competitive inhibition constant, Kic. This effect seems to be due to the 6-aryloxy-or 6-arylalkoxy substituent, because a natural PNP substrate adenine, as well as 2-chloroadenine, show mixed type inhibition with almost the same inhibition con stants Kiu and K1C . The most potent inhibition was observed for 6-benzylthio-2-chloro-, 6-benzyloxy-2-chloro-, 2-chloro-6-(2-phenyl-l-ethoxy), 2-chloro-6-(3-phenyl-l-propoxy)-and 2-chloro-6-ethoxypur-ines (Kiu = 0.4, 0.6, 1.4, 1.4 and 2.2 [im, respectively). The i?-stereoisomer o f 2-chloro-6-(l-pheny-l-ethoxy)purine has Kiu = 2.0 ^im, whereas inhibition o f its S counterpart is rather weak (IC50> 12 jim). More rigid (e.g. phenoxy-), non-planar (cyclohexyloxy-), or more bulky (2,4,6-trimethylphenoxy-) substituents at position 6 of the purine base gave less potent inhibi tors (IC50 = 26, 56 and >100 [im, respectively). The derivatives are selective inhibitors of hexameric "high-molecular mass" PNPs because no inhibitory activity vs. trimeric Cellulomo-nas sp. PNP was detected. By establishing the ligand-dependent stabilization pattern of the E. coli PNP it was shown that the new derivatives, similarly as the natural purine bases, are able to form a dead-end ternary complex with the enzyme and orthophosphate. It was also shown that the derivatives are substrates in the reverse synthetic direction catalyzed by E. coli PNP | | | |
Reference
| Z. Naturforsch. 54c, 1055—1067 (1999); received May 31/August 2 1999 | | | |
Published
| 1999 | | | |
Keywords
| 2-Chloropurines, Purine Nucleoside Phosphorylase, Inhibition, Escherichia coli, Phase Transfer Reactions | | | |
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| default:Reihe_C/54/ZNC-1999-54c-1055.pdf | | | | Identifier
| ZNC-1999-54c-1055 | | | | Volume
| 54 | |
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