N-hydroxy Compound Research Articles

Investigation of N-hydroxythalidomide in vitro stability and comparison to other N-substituted derivatives

The stability of N-substituted derivatives of thalidomide was studied and compared to that of thalidomide itself. Nitrogen atom included in glutarimide ring was successively substituted by a hydroxy group, a methyl acetate group, and an ethyl group. Lipophilicities of these compounds were determined using the method based on experimental determinations of partition coefficients developed by Hansch. Hydroxy group led to a decrease of lipophilicity. Substitution of the nitrogen atom by an ethyl group or a methyl acetate group allowed an increase of lipophilicity. Relative stabilities of each compound were determined under physiological conditions: pH (7.4) and temperature (37 °C) using high performance liquid chromatography procedure. The program Sigma Plot was used to fit experimental data in order to obtain the half-lifes of thalidomide and its analogs. In the case of substitution by an ethyl group, the increase of lipophilicity (Δlog P = 0.36) was in agreement with a higher stability in aqueous medium. In the case of methyl acetate group, hydrolysis of the cycle was chemically favoured despite a higher lipophilicity compared to those of thalidomide. In the case of N-hydroxy compound, the decrease in lipophilicity was not sufficient to affect the stability.

Uses of hydroxamic acids and of N-alkoxyimidoyl halides in organic synthesis

Although N-hydroxyamides (1) have been known for over a century, the chemistry of 1 is still relatively unexplored. The scope of the present review is a survey of the recent advances of the chemistry of 1 and its derivatives, particularly of new chemical reactions having synthetic utility in organic synthesis developed mainly in our laboratory. The review is divided into two sections. The first section described great utility of divalent positively-charged nitrogen species generated from 1 in synthesis. Electrophilic intramolecular cyclization with an acylnitrenium ion generated from an N-methoxy- or an N-allyloxy-N-chloroamide with anhydrous zinc acetate in nitromethane gave an N-methoxy- or an N-allyloxy nitrogen heterocyclic compound, deprotection of which led to formation of the corresponding N-hydroxy compound. Treatment of an N-hydroxy- or an N-methoxy-N-arylamide and the corresponding lactam with various reagents results in removal of the hydroxy or methoxy function and introduction of nucleophiles at the ortho or para position of the aromatic ring. These methodologies were successfully applied by us for the synthesis of the alkaloid, eupolauramine and for new oxindoles related to the alkaloid, gelsemine, by others. The second section described great utility of N-alkoxyimidoyl halides (2) synthesized from 1. Compounds 2 were readily transformed to other functions such as aldehydes, cyanides, and oximes. This methodology was successfully applied to the synthesis of omega-N-hydroxy-alpha-amino acids in optically pure form which were the key intermediates for the synthesis of hydroxamate-containing siderophores.

Glucuronidation of N-hydroxy metabolites of N-acetylbenzidine.

Glucuronidation of N-hydroxy arylamines is thought to be a necessary step in their initiation of bladder cancer. This was evaluated for the N-hydroxy metabolites of N-acetylbenzidine (ABZ). N'-Hydroxy-N-acetylbenzidine (N'-HA), N-hydroxy-N-acetylbenzidine (N-HA) and N-hydroxy- N,N'-diacetylbenzidine (N-HDA) were synthesized. Except for N'-HA, these compounds were quite stable. Ascorbic acid and/or acidic pH increased the stability of N'-HA. When each N-hydroxy compound was added to reaction mixtures containing [14C]UDP-glucuronic acid, 3 mM ascorbic acid and human liver microsomes a new product was detected by HPLC. Emulgen 911 was a better detergent than Triton X-100 for expressing microsomal activity, with maximal glucuronidation observed with 0.3% Emulgen 911. At 0.125 mM amine the rate of glucuronidation was N-HDA >> N'-HA = benzidine > ABZ > N-HA. In contrast, at 0.5 mM amine the rate of glucuronidation of N-HA was only exceeded by N-HDA. At pH 5.5 and 37 degrees C the t1/2 for the enzymatically prepared glucuronide conjugates of ABZ, N'-HA and N-HA were 7.5 min and 3.5 and 1.8 h respectively. For N-HDA > 90% of this glucuronide remained after 24 h. At pH 7.4 and 37 degrees C the t1/2 for the glucuronide conjugates of ABZ and N-HA were 2.3 and 2 h respectively, with the amounts remaining after 24 h for N'-HA and N-HDA being 75 and 90% respectively. At pH 6.5 the t1/2 for N'-HA was 14 h. Thus only glucuronides of ABZ and N'-HA exhibit pH-dependent changes in t1/2. Compared with ABZ, glucuronides the N-hydroxy metabolites are more stable at acidic pH. Acidic urine would be more likely to hydrolyze the glucuronide conjugate of ABZ than those of its N-hydroxy metabolites. Because these results are different from that hypothesized for arylmonoamines, a new model was developed to explain the role of N-oxidation, N-glucuronidation and N-acetylation in the carcinogenesis of benzidine, an aryldiamine.

Cyclization with Nitrenium Ions Generated from N-Methoxy- or N-Allyloxy-N-chloroamides with Anhydrous Zinc Acetate. Synthesys of N-Hydroxy- and N-Methoxynitrogen Heterocyclic Compounds

Electrophilic intramolecular aromatic substitution with an N-methoxy- or an N-allyloxy-acylnitrenium ion, generated by treatment of an N-methoxy- or an N-allyloxy-N-chloroamide with anhydrous zinc acetate in nitromethane, leads to formation of a nitrogen heterocyclic compound bearing an N-methoxy- or N-allyloxy group. The latter is readily converted to the corresponding N-hydroxy compound by palladium-catalyzed removal of the allyl group

Peptide synthesis by means of polymer-anchored N-hydroxy compound. 1. Preparation of simple peptides

Abstract 6-Acetamido-1-hydroxy-3-trifluoromethylindazole ( 5 ) was incorporated into either a Merrifield bead-type chloromethylated copolystyrene with 2% divinylbenzene or a chloromethylated polystyrene-polypropylene composite fiber-type polymer to obtain 7a and 8a , respectively. Deprotection of the tetrahydropyranyl group of 7a and 8a with hydrochloric acid afforded 7b and 8b , respectively. From 7b , the p -chlorobenzensulfonate 7d , the diphenylphosphate ester 7e , the diphenylphosphinate ester 7f and the bis(2-oxo-3-oxazolidinyl)phosphinate ester 7g of the above polymer-anchored 1-hydroxyindazole derivative 7b were synthesized and from 8b , the p -chlorobenzenesulfonate 8d was obtained. These compounds were examined in the synthesis of Z-Val-GlyOEt; the best result was obtained with 7d in N , N ′-dimethylformamide. Other simple peptides were also synthesized with 7d in good yields. To test the applicability of this method further, compound 7d was used to synthesize an intermediate of the melanocyte stimulating hormone-release-inhibiting factor, Z-Pro-Leu-GlyOEt; the yield was comparable with that from the conventional solution method. Also described is the solvent effect on the peptide yield.

Synthesis of 3-amino-3-methyl-2-azetidinone-1-sulfonic acid and its derivatives

N-Benzyloxy-2-(N-tert-butoxycarbonyl) amino-2-hydroxymethylpropionamide (8) was synthesized from methyl DL-isocyanopropionate (2). Compound 8 was treated with diethyl azodicarboxylate and triphenylphosphine to give β-lactam derivative (9), which was hydrogenolized with H2/Pd-C to the N-hydroxy compound (10) followed by treatment with TiCl3 to give the unsubstituted β-lactam derivative (11). Sulfonation of 11 with a pyridine-sulfur trioxide complex and deprotection with formic acid afforded a key intermediate, DL-3-amino-3-methyl-2-azetidinone-1-sulfonic acid (12). The desired 3-N-acylamino-3-methyl-2-azetidinone-1-sulfonic acid derivatives (13a, 13c and 13e) were obtained by acylation of 12. None of the compounds (13a, 13c and 13e) showed antibacterial activity, although the 4α-methyl counterparts (13f) had some activities against gram-negative bacteria.

ChemInform Abstract: N‐HYDROXYACETAMINOPHEN: A POSTULATED TOXIC METABOLITE OF ACETAMINOPHEN

AbstractAls Metaboliten von N‐Hydroxyacetaminophen (I) werden die Verbindungen (II) bis (IV) festgestellt.

N-hydroxyacetaminophen: a postulated toxic metabolite of acetaminophen.

The decomposition of N-hydroxyacetaminophen has been shown to occur via an initial first-order dehydration step to N-acetyl-p-benzoquinone imine with a rate constant at pH 7.6 of 8.66 x 10(-3) min-1 and a half-life of 80 min. This is followed by a complex reaction between the quinone imine and the N-hydroxy compound to ultimately yield p-nitrosophenol and acetaminophen. The glucuronide and sulfate conjugates of N-hydroxyacetaminophen have been observed as urinary metabolites of N-hydroxyacetaminophen. No N-hydroxylated metabolites were found among the metabolites of acetaminophen. These results have been interpreted to show that N-hydroxyacetaminophen is not a metabolite of acetaminophen. It is proposed that the hepatotoxicity and nephrotoxicity of acetaminophen are mediated by a direct oxidation of acetaminophen to the toxic reactive intermediate N-acetyl-p-benzoquinone imine by the cytochrome P450 dependent mixed-function oxidase system.

Synthesis of the urinary glucuronic acid conjugate of n-hydroxy-4-aminobiphenyl

The glucuronic acid conjugate of N-hydroxy-4-aminobiphenyl believed to be the carrier form responsible for transporting the active N-hydroxy compound from its site of formation in the liver to its site of carcinogenic action in the bladder has been prepared synthetically. The synthetic conjugate is identical by infrared and chromatographic analyses with the conjugate isolated from urine, thus unequivocally establishing its structure as an N--C conjugate, sodium (N,4-biphenyl-N-hydroxy-D-glucuronosylamine).

Phenobarbital-mediated increase in ring- and N-hydroxylation of the carcinogen N-2-fluorenylacetamide, and decrease in amounts bound to liver deoxyribonucleic acid

The effect of phenobarbital (PB) pretreatment of young male rats on the metabolism in vivo and in vitro of the carcinogen N-2-fluorenylacetamide (FAA) was studied. PB increased the urinary excretion of 14C from labeled FAA, mainly as met-abolites conjugated with glucuronic acid. There was a small drop in excretion of sulfuric acid conjugates. In the glucosiduronic acid fraction, there were increases in the N- and 7-hydroxy derivatives of FAA and a decrease in the 5-hydroxy compound, while the 3-hydroxy metabolite was virtually unchanged. The concentration of metabolites of FAA in the liver was considerably lower, as was the amount of isotope bound to DNA. This important finding, correlated with a reduced carcinogenicity of FAA in rats given PB, is ascribed to increased conjugation with glucuronic acid and lesser formation of sulfate esters. The microsomal fraction in vitro from the livers of young rats yielded metabolites of FAA, in decreasing order, hydroxylated at 7-, 5-, N- and 3-. Carbon monoxide significantly inhibited formation of the 7-hydroxy metabolite but elevated somewhat that of the N-hydroxy compound. Pretreatment with PB increased cytochrome P-450 and hydroxylation at all positions 2- to 4-fold, the greatest effect being with N-hydroxy-FAA. With microsomes from PB-treated rat livers, carbon monoxide depressed hydroxylation at the 3-position, while N-hydroxylation was least affected. Because hydroxylation of FAA occurs at several well-defined ring positions and on the amido nitrogen, FAA is a good substrate to explore the mechanisms of hydroxylation reactions. The data obtained suggest that these metabolic reactions are performed by a family of related enzyme systems.

Colon carcinogens: their metabolism and mode of action.

Colon cancer in man almost certainly is induced by environmental factors, probably consumed with food. Except for one breed of hamsters, colon cancer is infrequent in laboratory or domestic animals. Reliable induction of colon cancer can be achieved with 2 broad classes of chemicals: 1. derivatives of 3-methyl-4-aminobiphenyl, and 2. derivatives of 1, 2-dimethylhydrazine, including the plant product cycasin. Sometimes an unknown ingredient of bracken fern causes cecal or colonic cancers. The metabolism of 4-aminobiphenyl derivatives involves, among other steps, N-hydroxylation, conjugation of the metabolite with glucuronic acid, secretion of the conjugate in bile, liberation of the free N-hydroxy compound, the postulated active intermediate, by action of bacterial flora in large intestine where reaction with significant tissue, cell, and molecular elements occurs. After oral intake of cycasin the aglycone methylazoxymethanol is likewise freed for reaction in colon by bacterial enzymes. 1,2-Dimethylhydrazine yields azoxymethane which is hydroxylated in liver, conjugated with glucuronic acid and secreted in bile, again to be split in gut with liberation of the active methylazoxy-methanol. On the basis of these models, colon cancer formation in man may involve: 1. ingestion of complex carcinogens with diet, with liberation of the active agent by bacterial enzymes; 2. ingestion of procarcinogens, absorption, metabolism by liver, secretion in bile, and freeing of active agent in gut; 3. production of active agent by bacterial flora in gut by conversion of select food precursors, and 4. production of a mycotoxin by an intestinal microorganism.

761. Organochlorine pesticide levels in body fat of man: Hoffman, W. S., Fishbein, W. I. & Andelman, M. B. (1964). The pesticide content of human fat tissue. Archs envir. Hlth9, 387

The effect of phenobarbital (PB) pretreatment of young male rats on the metabolism in vivo and in vitro of the carcinogen N-2-fluorenylacetamide (FAA) was studied. PB increased the urinary excretion of 14C from labeled FAA, mainly as met-abolites conjugated with glucuronic acid. There was a small drop in excretion of sulfuric acid conjugates. In the glucosiduronic acid fraction, there were increases in the N- and 7-hydroxy derivatives of FAA and a decrease in the 5-hydroxy compound, while the 3-hydroxy metabolite was virtually unchanged. The concentration of metabolites of FAA in the liver was considerably lower, as was the amount of isotope bound to DNA. This important finding, correlated with a reduced carcinogenicity of FAA in rats given PB, is ascribed to increased conjugation with glucuronic acid and lesser formation of sulfate esters. The microsomal fraction in vitro from the livers of young rats yielded metabolites of FAA, in decreasing order, hydroxylated at 7-, 5-, N- and 3-. Carbon monoxide significantly inhibited formation of the 7-hydroxy metabolite but elevated somewhat that of the N-hydroxy compound. Pretreatment with PB increased cytochrome P-450 and hydroxylation at all positions 2- to 4-fold, the greatest effect being with N-hydroxy-FAA. With microsomes from PB-treated rat livers, carbon monoxide depressed hydroxylation at the 3-position, while N-hydroxylation was least affected. Because hydroxylation of FAA occurs at several well-defined ring positions and on the amido nitrogen, FAA is a good substrate to explore the mechanisms of hydroxylation reactions. The data obtained suggest that these metabolic reactions are performed by a family of related enzyme systems.

Torsion of the gall-bladder.

Studies of structure-transacylation relationships for a series of acylhydroxamic acids of chlorinated biphenyl ethers and their related compounds by rat liver N-arylacylhydroxamic acid-dependent N-acyltransferase (AHNAT) are described. In the transacylation of 4-aminoazobenzene catalyzed by AHNAT, 4-substituents (chloro, phenoxy, and mono-, di-, and trichlorophenoxy groups) of N-phenylacetohydroxamic acid enhanced the ability of the unsubstituted hydroxamic acid to serve as acetyl donors. As to the number of chlorines in the phenoxy group, the activity increased with decreasing number from three to zero. Of the monochlorophenoxy compounds, the 49-chloro compound was the most effective acetyl donor. In 3-substituents (chloro and phenoxy groups) of N-phenylacetohydroxamic acid, the 3-chloro compound was an effective acetyl donor similarly to the 4-chloro compound, whereas the 3-phenoxy compound was 48% as active as the 4-phenoxy compound. None of 2-substituted N-phenylacetohydroxamic acids examined showed transacetylation activity. As to the effect of acyl group structure on the activity, N-propionyl, N-glycoloyl, and N-formyl derivatives of the 4-(49-chlorophenoxy) compound were only 4, 2, and 0% as active as the corresponding acetyl compound, respectively. Esterification of the N-arylacetohydroxamic acid decreased the activity; O-acetyl, O-methyl, O-glucosyl, and O-glucuronosyl derivatives of the 4-(49-chlorophenoxy) compound were 35, 7, 0, and 0% as active as the corresponding N-hydroxy compound, respectively.