Synthesis and biological evaluation of modified purine homo-N-nucleosides containing pyrazole or 2-pyrazoline moiety.

9-Substituted (pyrazol-5-yl)methyl- or (2-pyrazolin-5-yl)methyl-9H-purines were synthesized from 9-allyl-6-chloro-9H-purine through the 1,3-dipolar cycloaddition reaction with nitrile imines, prepared in situ from the corresponding hydrazone and NBS/Et3N under MW or from hydrazinoylchloride and Et3N under reflux. The coupling of new 6-chloropurines with amines in H2O under microwaves resulted quantitatively to modified pyrazol-5-yl- or 2-pyrazolin-5-yl adenine homo-N-nucleosides. The new compounds were tested in vitro for their ability to: (i) interact with 1,1-diphenyl-2-picryl-hydrazyl (DPPH), (ii) inhibit lipid peroxidation, (iii) inhibit the activity of soybean lipoxygenase, (iv) inhibit in vitro thrombin and for (v) their antiproliferative and cytotoxic activity. Pyrazolines were found to be more potent in vitro. Compound 7a exhibited satisfactory combined antioxidant and anti-lipid peroxidation activity, inhibition of lipoxygenase (89%) and thrombin inhibitory ability, whereas compound 7b exhibited high lipoxygenase inhibitory activity in combination to significant anti-thrombin activity. No compound exhibited a significant cytotoxic activity, while all showed moderate antiproliferative activity.

Synthesis of modified homo-N-nucleosides from the reactions of mesityl nitrile oxide with 9-allylpurines and their influence on lipid peroxidation and thrombin inhibition.

9-(3-Mesityl-4,5-dihydroisoxazol-5-yl) homo-N-nucleosides were prepared from the 1,3-dipolar cycloaddition reactions of mesityl nitrile oxide with 9-allyl derivatives of 6-chloropurine, 6-piperidinylpurine, 6-morpholinylpurine, 6-pyrrolidinylpurine, and 6-N,N-dibenzoyladenine. The new compounds were tested in vitro for their ability: (i) to interact with 1,1-diphenyl-2-picryl-hydrazyl (DPPH) stable free radical, (ii) to inhibit lipid peroxidation, (iii) to scavenge the superoxide anion, (iv) to inhibit the activity of soybean lipoxygenase, and (v) to inhibit in vitro thrombin. Most of them found to be potent thrombin inhibitors and to inhibit in vitro lipid peroxidation. The majority of the compounds showed significant lipoxygenase inhibitory activity.