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-arylalkoxypurines. 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 . = 0.4, 0.6, 1.4, 1.4 and 2.2 [im, respectively). The i?-stereoisomer o f 2-chloro-6-(lpheny-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 Cellulomonas sp. PNP was detected. 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-ethoxypurines (KiuBy 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

Interactions of 2,6-substituted purines with purine nucleoside phosphorylase from Helicobacter pylori in solution and in the crystal, and the effects of these compounds on cell cultures of this bacterium

“…The synthesis of known compounds 6-benzyloxy-2-chloropurine ( 6BnO-2Cl-Pu, MW 260.68 g/mol), 6-benzylthio-2-chloropurine ( 6BnS-2Cl-Pu , MW 276.74 g/mol), and 6-benzylthiopurine ( 6BnS-Pu , MW 242.3 g/mol) 22 , 26 is described in the Supplemental Materials .…”

“…Therefore, in this study, we decided to check the influence of inhibitors of PNP from H. pylori on the growth rates of this bacterium in cell culture, and obtain a high-resolution three-dimensional structure of the enzyme-inhibitor complexes to characterise details of the enzyme-ligand interactions. As PNP from H. pylori is similar to the E. coli PNP 19–21 we decided in the first attempt to check some known inhibitors of the latter enzyme, namely, 2,6-substituted purines 22 .…”

Hoogsteen vs. Watson–Crick Base Pairing: Incorporation of 2‐Substituted Adenine‐ and 7‐Deazaadenine 2′‐Deoxy‐β‐D‐ribonucleosides into Oligonucleotides

“…Next, a series of 2-(trifluoromethyl)-2'-deoxyadenosines, 19 -21, were prepared (Scheme 3). For this purpose, the chromophore 16 [46] was glycosylated with the halogenose 17 [47] using NaH in MeCN. The resulting protected nucleoside 18 was obtained in 53% yield.…”

“…We now synthesized the corresponding oligomer 5'-d(2-T) 6 (46) in which the modified base lacks the N(7)-atom. Temperature-dependent UV measurements revealed no complex formation, a finding which implies that the parent oligomer, 48 · 48, represents most likely a Hoogsteen duplex.…”

“…Therefore, we synthesized next a series of oligonucleotides in which single dA residues are replaced by 2-methoxy-2'-deoxyadenosine (1b), a nucleoside which should force the 6 (46) 3840 3845…”