- Non-peptidic inhibitors of human neutrophil elastase: The design and synthesis of sulfonanilide-containing inhibitors
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A novel series of pivaloyloxy benzene derivatives has been identified as potent and selective human neutrophil elastase (HNE) inhibitors. Convergent syntheses were developed in order to identify the inhibitors which are intravenously effective in an animal model. A compound of particular interest is the sulfonanilide-containing analogues. Structure-activity relationships are discussed. Structural requirements for metabolic stabilization are also discussed.
- Imaki, Katsuhiro,Okada, Takanori,Nakayama, Yoshisuke,Nagao, Yuuki,Kobayashi, Kaoru,Sakai, Yasuhiro,Mohri, Tetsuya,Amino, Takaaki,Nakai, Hisao,Kawamura, Masanori
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p. 2115 - 2134
(2007/10/03)
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- Structure-reactivity correlations in the dissociative hydrolysis of 2′,4′-dinitrophenyl 4-hydroxy-X-benzenesulfonates
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The hydrolysis reactions of several title esters in water at 60°C follow the rate law kobs = (ka + kb[OH-])/(1 + αH/Ka), where Ka is the ionization constant of the hydroxy group of the ester and kb is the second-order rate constant for the SN2(S) attack of hydroxide ion on the ionized ester. Hammett and Br?nsted correlations are consistent with a previous proposal that the mechanism related to ka is dissociative. An unusual relationship between ka values and redox equilibrium constants for substituted quinones is found to hold: this finding further supports the dissociative nature of the pathway related to ka.
- Cevasco, Giorgio,Thea, Sergio
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p. 6814 - 6817
(2007/10/03)
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- Sulfonation and sulfation in reactions of C-methylated phenols and anisoles with sulfur trioxide. 4-Substituted phenyl hydrogen sulfates: effective reagents for transsulfonation
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The sulfation and sulfonation of the methyl- and dimethylphenols with 0.9 and 4.0 equiv. of SO3 in nitromethane at 0 deg C have been studied.On using 0.9 equiv. of SO3, the sulfonic acid product distributions are determined by the ortho- and para-directing effect of the activating hydroxy substituent.In the reactions with 4.0 equiv. of SO3, the sulfonic acid product distributions are affected by the predominant initial formation and the subsequent sulfonation of the corresponding phenyl hydrogen sulfates, of which the bulky OSO3H substituent is electronically deactivating and (mainly) para-directing.For comparison, the sulfonation of the methylanisoles, phenyl methanesulfonate and 2,3-dihydrobenzofuran was also studied.The sulfonation of 1,3-dimethoxybenzene in (2H8)dioxane at 17.0 deg C has been studied using 4-substituted phenyl hydrogen sulfates as transsulfonating agents.The transsulfonation was found to be first order with respect to the phenyl hydrogen sulfates and independent of the 1,3-dimethoxybenzene concentration.The reaction constant of the transsulfonation reaction was determined to be ρ=2.0+/-0.2.
- Goossens, Hans D.,Lambrechts, Hans J. A.,Cerfontain, Hans,Wit, Peter de
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p. 426 - 430
(2007/10/02)
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- Aromatic Sulphonation. Part 91. The Sulphonation of Anisole, Phenol, Phenyl Methanesulphonate, Potassium Phenyl Sulphate, and a Series of Methyl-, Bromo-, and Chloro-substituted Anisoles and Phenols in Concentrated Aqueous Sulphuric Acid
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The (homogeneous) sulphonation of a number of aromatic ethers and alcohols, viz. anisole (1), 3-methyl- (2), 4-methyl- (3), 2-bromo- (4), 4-bromo- (5), 2-chloro- (6), and 4-chloro-anisole (7), phenol (8), 2-methyl- (9), 3-methyl- (10), 4-methyl- (11), 4-bromo- (12), 2-chloro- (13), and 4-chloro-phenol (14), phenyl methanesulphonate (15), and potassium phenyl sulphate (16) in concentrated aqueous sulphuric acid at 25.0 deg C has been studied, and rates and isomer distributions have been determined.The sulphonation is first-order in the aromatic substrate, and from the rate measurements it is concluded that the species undergoing sulphonation in the phenyl ring is an unprotonated substrate species.In the lower acid concentrations the sulphonating entity is H3SO4(1+).With increasing sulphuric acid concentration there is a gradual change-over in the sulphonating entity from H3SO4(1+) to H2S2O7.The acid concentrations of equal rate contribution by the two entities for anisole and phenol are 87 and 90 +/- 1percent, respectively.Sulphonation on the oxygen atom (i.e., sulphation) does not occur.The o/p-ratios for (1) and (8) do not vary over the studied sulphuric acid range of 75-90percent H2SO4.Partial rate factors for the 2- and 4-position of (1) and (8) are reported.The very low partial rate factors for the 4-substitution of (1) and (8) and the observed extreme suppression and compression of the reactivities of the substrates (1)-(14) are ascribed to hydrogen bonding of the substrates with the acidic solvent species present.It is tentatively suggested that the relatively high contents of sulphonation ortho to -OR with anisole (36percent) and phenol (48percent) are due to specific complexation of the substrates with the sulphonating electrophile.
- Cerfontain, Hans,Lambrechts, Hans J. A.,Schaasberg-Nienhuis, Zwaan R. H.,Coombes, Robert G.,Hadjigeorgiou, Panicos,Tucker, Geoffrey
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p. 659 - 668
(2007/10/02)
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- Aromatic Sulphonation. Part 92. Sulphonation of the Three Methylphenols and the Six Dimethylphenols in Concentrated Aqueous Sulphuric Acid; and the Isomerization of Some of the Resulting Sulphonic Acids and of m-Xylene-2- and o-Xylene-3-sulphonic Acid
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The isomer distributions for the mono- and di-sulphonation of the three methylphenols in 81.6-90.0percent sulphuric acid and of the six dimethylphenols in 84.9percent sulphuric acid at 35 deg C have been determined by means of 1H n.m.r. spectroscopy.Products that would result from demethylation, disproportionation, or ipso-substitution have not been observed.The monosulphonation isomer distribution of each of the three methylphenols is independent of the sulphuric acid concentration. 2,4-Dimethylphenol in 84.9percent H2SO4 yields 19percent 5- and 79percent 6-sulphonic acid, and 2,6-dimethylphenol yields 28percent 3- and 72percent 4-sulphonic acid.With the phenols (2), (3), (5),and (7), which have positions both ortho and para to the -OH substituent available for sulphodeprotonation, the yield of ortho-substitution is relatively high, viz. 44, 45, 36, and 27percent, respectively.The mono- and di-sulphonic acids of which the sulpho group is between the -OH and an -Me group are unstable under the reaction conditions employed, with the exception of the 3,5-dimethylphenol-2-sulphonic acid.It is proposed that their isomerization proceeds by protiodesulphonation followed by resulphonation to yield the more stable sulphonic acid isomer(s).From a kinetic analysis of the calculated first-order rate coefficients for protiodesulphonation, it is concluded that the unprotonated substrate species is the entity undergoing the protiodesulphonation.
- Lambrechts, Hans J. A.,Schaasberg-Nienhuis, Zwaan R. H.,Cerfontain, Hans
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p. 669 - 676
(2007/10/02)
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