Byline: SABAHAT SARDAR, TASHFEEN AKHTAR, SHAHID HAMEED AND KHALID MOHAMMED KHAN
Summary: Synthesis of pyrazolone, its derivatives is of particular interest in heterocyclic chemistry due to their pharmaceutical importance. In the present study arylsulfonyl (1a-f , 2a-f) , carboxamide (3a-e) derivatives of 3-methyl-1H-pyrazol-5(4H)-one were synthesized. The reaction of pyrazolone with arylsulfonyl chlorides resulted in mono (1a-f) , disubstituted (2a-f) arylsulfonyl derivatives of 3-methyl-1H-pyrazol-5(4H)-one. On the other h,, the pyrazolone on treatment with different isocyanates yielded respective carboxamides (3a-e). The synthesized compounds were screened for urease inhibition, antibacterial, antioxidant assays, exhibit promising urease inhibition. Compound 1e was observed to be most active urease inhibitor in the series with 91.9 % inhibition. However, the antioxidant, antibacterial activities of all the compounds were non-significant at non-toxic concentration.
Keywords: Pyrazolone derivatives, Carboxamides, Urease inhibition, Antibacterial, Antioxidant.
Pyrazolone moiety is an appealing template for medicinal chemistry as it has been a part of many drugs . Pyrazolone derivatives have been the interest of research owing to diverse applications such as antioxidant, antimicrobial, cytotoxic, anticancer, antiviral, anticonvulsant, antibacterial , molluscicidal activities [2-7]. They also exhibit antitumor, antihypoglycemic, antifungal, analgesic, antipyretic , anti-inflammatory activities  besides being used as dyes as well [9-11]. Pyrazolones have also been employed in the synthesis of other heterocycles , in the separation of lanthanides , dyes preparation . They gave a great impetus to the research for potential pharmacological drugs carrying pyrazolone substituents. The pyrazolone nucleus exhibits structural feature to be a potential urease inhibitor, which is not an explored area of the pyrazolone chemistry.
The urease is a nickel-dependent metalloenzyme that catalyzes the hydrolysis of urea into an ammonium ion, carbamate which spontaneously breaks down to form ammonia , carbon dioxide . The inhibitors of urease have been extensively studied because of their potential use in diseases such as Helicobacter pylori-induced peptic ulcer , urinary lithiasis, pyelonephritis , hepatic coma . Urease has been reported to be responsible for the development of acute pyelonephritis by participating in urolithiasis , is also involved in infection-induced arthritis . In order to control the urease activity, urease inhibitors have also been used along with fertilizers to control the rate of urea-hydrolysis in soil .
Heterocycles exhibiting urease inhibition have also been synthesized , reported by our group in the past few years [19-23]. We herein report some new pyrazolone derivatives, synthesized to explore their potential urease inhibition properties.
Results , Discussion
The reaction sequences employed for the synthesis of target pyrazolone derivatives is illustrated in Scheme-1. All the synthesized compounds were characterized using modern spectroscopic techniques, screened for their antibacterial, antioxidant , urease inhibition assays.
Arylsulfonyl derivatives of 3-methyl-1H- pyrazol-5(4H)-one were synthesized by the reaction of pyrazolone with various arylsulfonyl chlorides in the presence of triethylamine . On TLC two products were observed, which were separated by silica gel column chromatography , identified as mono- , disubstituted pyrazolones. The synthesis was later optimized by 1:1 , 1:2 molar equivalents of pyrazolone , arylsulfonyl chloride to afford mono- (1a-f) , disubstituted (2a-f)...