N-Substituted Hydroxyureas as Urease Inhibitors.

Abstract

Persons infected with Helicobacter pylori are exposed to a high risk for stomach cancer. As eradication therapy, a combination of antibiotics and a proton inhibitor has been adopted. However, this therapy is unsatisfactory due to the induction of drug-resistance. Thus, the urease activity of H. pylori may be an attractive target for drug design of an anti-H. pylori agent. Hydroxyurea (1), an antineoplastic agent, 1) has been known to inhibit various ureases from microorganisms and vegetables, including H. pylori 2,3) and jack bean. 4)In the present work, we have searched for a potent therapeutic drug through the derivatization of 1 to N-substituted hydroxyureas. Phenyl-or low alkyl-substituted hydroxyureas were first synthesized as shown in Table 1. Thus, aniline was converted to the isocyanate with triphosgene in the two-phase system of CH 2 Cl 2 and aq. Na 2 CO 3 , which was treated with O-benzylhydroxylamine to give N-(benzyloxy)-NЈ-phenylurea (5a). This compound was hydrogenated over 10% Pd-C to give the desired N-hydroxy-NЈ-phenylurea 5) (5). Further, N-ethyl-NЈ-hydroxyurea 6) (2), N-hydroxy-NЈ-propylurea 6) (3) and N-butyl-NЈ-hydroxyurea 7) (4) were prepared by treating the corresponding isocyanates with hydroxylamine hydrochloride in aq. NaOH solution, respectively, according to the procedure by Harmon, et al. 6)The inhibitory activities against jack bean urease were measured as explained in a separate paper 8) : the control solution was prepared by dissolving Phenol Red and blank solvent (H 2 O, EtOH, or dimethyl sulfoxide (DMSO)) in 0.1 M phosphate buffer (pH 7.7), whereas the sample solution was made by dissolving Phenol Red and a test sample in a blank solvent in 0.1 M phosphate buffer (pH 6.7). These control and sample solutions, after addition of the urease solution, were successively pre-incubated at 30°C for 30 min, and diluted 6-fold with the control buffer of pH 7.7 and the buffered urea solution of pH 6.7, respectively, according to the colorimetric timing method.9-11) The absorbance at 560 nm of the resulting control solution was adjusted to zero on the spectrophotometer, and the time interval for the absorbance of the sample solution to reach zero was measured at 560 nm. The percentage inhibition (%) of each sample was calculated based on the following equation. (17) 12) were synthesized using the procedure of Harmon, et al.,6) but with the addition * To whom correspondence should be addressed. Biotechnology, Faculty of Engineering, Kansai Univeristy; 3-3-35 Yamate-cho, Suita, Osaka 564-8680, Japan: and b Faculty of Pharmaceutical Sciences, Kinki University; 3-4-1 Kowakae, Higashiosaka, Osaka 577-8502, Japan. Received April 22, 2002; accepted June 10, 2002 In order to seek a urease inhibitor more potent than hydroxyurea (1), its alkyl-or phenyl-substituted derivatives were synthesized and evaluated for their effect on the jack bean urease. Of 16 compounds tested, m-methyl-(10) and m-methoxy-phenyl substituted hydroxyurea (13) showed the most potent inhibitory activities against the...

An Experimental and Computational Approach to Understanding the Reactions of Acyl Nitroso Compounds in [4 + 2] Cycloadditions

“…Compounds 1-12 have been reported elsewhere [31][32][33][34][35][36][37][38][39][40][41][42] using different procedures to those described here.…”

Synthesis, antibacterial and cytotoxic activity evaluation of hydroxyurea derivatives

“…Among them, only 2 reacted with hydrogen in the presence of palladium/carbon (Pd/C, 10 %), which resulted in 1-(N-hydroxycarbamoyl)benzotriazole (5) in quantitative yield. Uesato et al (16) reported the use of benzyloxyisocyanate as a useful building block in the synthesis of hydroxyurea derivatives, while Butula and Jadrijevi}-Mladar Taka~ (14) reported that 2, when heated over 100°C liberates benzyloxyisocyanate which is further trimerized to N,N',N''-tribenzyloxy-triazinone (10), and yields a minor product N,N',N''--tribenzyloxybiuret (11). In this work, we utilized 2 as a donor of benzyloxyisocyanate, which is very useful for the synthesis of hydroxyurea derivatives.…”

“…The corresponding hydroxyl derivatives, i.e., 1-(Nhydroxycarbamoyl)benzotriazole (5), N-hydroxybiuret (12) (20), 4-{[(hidroxy)carbamoyl]amino}benzoic acid (13), N-hydroxurea (14), N,N',N''-trihydroxybiuret (15) (20) and N,N',N''-trihydroxyisocyanuric acid (16) were obtained in quantitative yields. The synthetic routes and structures of isolated compounds are presented in Scheme 1, whereas their physicochemical data are summarized in Tables I and II. The synthesized set of compounds (Table I) represents different derivatives of hydroxyurea, which can be categorized into several subgroups, i.e., benzotriazole N-carbamoyl derivatives (2, 3, 4 and 5), cyclic-(10, 16 and 17) and acyclic hydroxyurea derivatives (7, 8, 9, 13 and 14), and biuret derivatives (6, 11, 12 and 15).…”

“…The white solid product was washed with HCl (pH 3) and water, recrystallized from ethyl acetate and hexane and dried over P 2 O 5 in vacuo. (5), N-hydroxybiuret (12), 4-(hydroxyaminocarbonyl)aminobenzoic acid (13), N-hydroxyurea (14), N,N',N''-trihydroxyisocyanuric acid (16) and N,N',N''-trihydroxibiuret (15) A mixture of 1-(N-benzyloxycarbamoyl)benzotriazole (2), N-benzyloxybiuret (6), 4-(benzyloxycabamoyl)aminobenzoic acid (7), N-benzyloxyurea (8), N,N',N''-tribenzyloxyisocyanuric acid (10) or N,N',N''-tribenzyloxybiuret (11) and 0.05 g palladium on carbon (Pd/C, 10%) in methanol (100 mL) was kept under hydrogen (r. t., normal pressure) for 1-10 hours. Pd/C was filtered off and methanol was evaporated.…”

“…The obtained products 5, 12, 13, 14, 16 and 15, respectively, were dried over P 2 O 5 in vacuum and were obtained in practically theoretical yields. (16) and its triacetyl ester (17) were prepared according to previously published procedures (6,14,15).…”