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  • Synthesis, characterization and biological activity of ring-substituted 6-benzylamino-9-tetrahydropyran-2-yl and 9-tetrahydrofuran-2-ylpurine derivatives.

Synthesis, characterization and biological activity of ring-substituted 6-benzylamino-9-tetrahydropyran-2-yl and 9-tetrahydrofuran-2-ylpurine derivatives.

Bioorganic & medicinal chemistry (2009-02-24)
Lucie Szücová, Lukás Spíchal, Karel Dolezal, Marek Zatloukal, Jarmila Greplová, Petr Galuszka, Vladimír Krystof, Jirí Voller, Igor Popa, Frank J Massino, Jan-Elo Jørgensen, Miroslav Strnad
ABSTRACT

In an attempt to improve specific biological functions of cytokinins routinely used in plant micropropagation, 33 6-benzylamino-9-tetrahydropyran-2-ylpurine (THPP) and 9-tetrahydrofuran-2-ylpurine (THFP) derivatives, with variously positioned hydroxy and methoxy functional groups on the benzyl ring, were prepared. The new derivatives were prepared by condensation of 6-chloropurine with 3,4-dihydro-2H-pyran or 2,3-dihydrofuran and then by the condensation of these intermediates with the corresponding benzylamines. The prepared compounds were characterized by elemental analyses, TLC, HPLC, melting point determinations, CI+ MS and (1)H NMR spectroscopy. The cytokinin activity of all the prepared derivatives was assessed in three classical cytokinin bioassays (tobacco callus, wheat leaf senescence and Amaranthus bioassay). The derivatives 6-(3-hydroxybenzylamino)-9-tetrahydropyran-2-ylpurine (3) and 6-(3-hydroxybenzylamino)-9-tetrahydrofuran-2-ylpurine (23) were selected, because of the high affinity of their parent compound meta-topolin (mT, 6-(3-hydroxybenzylamino)purine) to cytokinin receptors, as model compounds for studying their perception by the receptors CRE1/AHK4 and AHK3 in a bacterial assay. Both receptors perceived these two derivatives less well than they perceived the parent compound. Subsequently, the susceptibility of several new derivatives to enzyme degradation by cytokinin oxidase/dehydrogenase was studied. Substitution of tetrahydropyran-2-yl (THP) at the N(9) position decreased the turnover rates of all new derivatives to some extent. To provide a practical perspective, the cytotoxicity of the prepared compounds against human diploid fibroblasts (BJ) and the human cancer cell lines K-562 and MCF-7 was also assayed in vitro. The prepared compounds showed none or marginal cytotoxicity compared to the corresponding N(9)-ribosides. Finally, the pH stability of the two model compounds was assessed in acidic and neutral water solutions (pH 3-7) by high-performance liquid chromatography (HPLC).

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
4-Methoxybenzylamine, 98%
Sigma-Aldrich
6-Benzylaminopurine, suitable for plant cell culture
Sigma-Aldrich
6-Benzylaminopurine solution, 1 mg/mL, suitable for plant cell culture
Sigma-Aldrich
6-Benzylaminopurine, ReagentPlus®, ≥99.0% (HPLC)
Sigma-Aldrich
trans-Zeatin hydrochloride, suitable for plant cell culture, ≥97%
Sigma-Aldrich
Zeatin, BioReagent, suitable for plant cell culture, powder
Sigma-Aldrich
trans-Zeatin, BioReagent, suitable for plant cell culture, ≥97%
Sigma-Aldrich
6-(γ,γ-Dimethylallylamino)purine, BioReagent, suitable for plant cell culture, ≥98.5%
Sigma-Aldrich
6-(γ,γ-Dimethylallylamino)purine, BioReagent, suitable for plant cell culture, 1 mg/mL