Nitramine, 12. Mitt. Fluormethyl- und Azidomethyl-alkylnitramine

Nitramines, XII: N-Fluoromethyl- and N-Azidomethyl-N-alkylnitramines The N-chloromethyl-N-alkylnitramines 1 react with potassium fluoride and 18-crown-6 to give the unstable N-fluoromethyl-N-alkylnitramines 2 . With sodium azide the stable N-azidomethyl-N-alkylnitramines 3 are formed. With alkynes the latter cyclize to yield 1,2,3-triazoles, the structures of which were studied.     

Untersuchungen an 1,3-Thiazinen, 25. Mitt. Transacylierende N-Acyl-tetrahydro- und N-Acyl-dihydro-1,3-thiazin-derivate

1,3-Thiazines, XXV: Transacylating Derivatives of N-Acyltetrahydro- and N-Acyldihydro-1,3-thiazine Novel N-acyl-2-thioxo-3,4-dihydro-1,3-thiazine-4-ones 4 and N-acyl-tetrahydro-1,3-thiazine-2,4-diones 7 were preparee by acylation of the N-unsubstituted 1,3-thiazine derivatives 3 and 6 with acid chlorides. Their characteristics are compared with those of known N-acylthiazine derivatives.     

Isosteric conversion of protein carboxyl groups into carboxamide groups. II. Application to lysozyme

For isosteric conversion of carboxyl groups of proteins into amide groups, ammonolysis of protein esters under mild conditions was attempted. Ammonolysis of methyl esters of lysozyme and bovine serum albumin proved to be incomplete. Highly reactive N-ethylsalicylamide esters of guanylated lysozyme were therefore prepared by subjecting the protein to reaction with N-ethylbenz-isoxazolium ion at pH 4.2, 0°. Per molecule, 5–7 ester groups were introduced, with concomitant decrease of activity of 80–90%. Only 0.3 tyrosine was modified. On hydrolysis at pH 9.2 the activity was completely restored. At pH 7.9 three classes of ester groups could be distinguished: one group of high rate of hydrolysis (k₁ = 1.5 min^-1), three groups of intermediate rate (k₂ = 0.13 min^-1) and two groups of low rate (k³ = 0.018 min^-1). The intermediate rate approximated the rate of hydrolysis of the model compound benzoylglycine N-ethyl-salicylamide ester (k = 0.15 min^-1). Ammonolysis at pH 9.2 in 2.0 M ammonia/ ammonium acetate provided complete conversion of the ester groups into amide groups without restoration of activity, confirming the essentiality of certain carboxyl groups. In particular, rearrangement of the ester groups into relatively stable imide groups by O–N acyl migration was found to be completely absent. When native lysozyme was esterified with N-ethylbenzisoxazolium ion the activity did not completely return on hydrolysis.     

Investigation in the dipropylacetic acid series, C8 and C9 branched chain ethylenic acids and amides.

2-Propyl-2-pentenoic acid was prepared. Its stereochemistry was determined using the A.S.I.S.-effect. The dehalogenation by N,N-diethylaniline of some N-substituted 2-bromo-2,2-dipropyl-acetamides gave the corresponding unsaturated amides. The configurations of these compounds are discussed on the basis of NMR data obtained with and without complexation with tris(dipivaloylmethano)europium [Eu (DPM)₃].     

Enzymatic reduction of benzamidoxime to benzamidine

Strongly basic amidine functions are components of numerous active principles. Our investigations on the biotransformations of this functional group have provided evidence for the N-demethylation of N-methylbenzamidine and the N-hydroxylation of amidine functions without α-hydrogen atoms^{3, 4)}. The pharmacological and toxicological relevance of the N-oxygenations of amidine functional groups als been demonstrated.     

Nitramine, 19. Mitt. Zur Stabilität von Dialkylnitraminen

Nitroamines, XIX: The Stability of Dialkylnitroamines Dialkylnitroamines are sensitive to bases and give aldehydes, primary amines and nitrite ions. After treating the N-benzyl-N-methylnitroamines 1–3 with lithium diisopropylamide we succeeded in isolating the aldimines 4–6 . From N-benzyl-N-(cyanomethyl)nitroamine (7) (cyanomethylimino)benzaldehyde (9) was obtained, and N-benzyl-N-(ethoxycarbonylmethyl)nitroamine (8) reacted with sodium hydride to yield [(ethoxycarbonylmethyl)imino]benzaldehyde (10) .     

The in vitro N-oxygenation of N-tert.alkyl-substituted benzamidine

Studies of the N-Oxygenation of N-(tert.Alkyl)benzamidines in vitro N-tert.Butyl- and N-tert.octylbenzamidine ( 1a and b ) and their potential N-oxygenated metabolites, the amidoximes 2a and b , have been synthesized and characterized. N-tert.Butylbenzamidine 1a is N-oxygenated to the amidoxime 2a by aerobic incubation with non-induced microsomal fractions of rabbit liver homogenates and NADPH. This transformation supports the hypothesis that benzamidines undergo N-oxygenation by the cytochrome P-450 enzyme system when N-dealkylation is not possible (absence of hydrogen atoms in α-position to the amidine nitrogen atoms).     

Ringschlußreaktionen mit N-(Chlormethyl)carbimidoylchloriden, 2. Mitt. Umsetzungsprodukte mit N,N′-Dimethylthioharnstoff

Heterocyclisation Reactions with N-(Chloromethyl)carboximidoyl Chlorides, II: Reaction with N, N′-Dimethylthiourea N-(Chloromethyl)benzimidoyl chloride ( 1 ) and N, N′-dimethylthiourea ( 2 ) react to form the three isomeric triazine and thiadiazine derivatives 6 , 7 and 8 , which were separated by layer chromatography. Their structures were determined by ¹³C-NMR spectroscopy. The thiadiazine derivative 11 was isolated as a by-product. A mechanism is proposed for its formation.     

Barbitursäurederivate, 25. Mitt. Chirale N-Alkyl-norhexobarbitale

Chiral N-Alkylnorhexobarbitals Syntheses of the racemates and the enantiomers of the N-alkylnorhexobarbitals 2a --c are reported. The stereospecific condensations of disubstituted cyanoacetates with highly alkylated ureas proceed in the same direction as with N-methylurea.     

Antimykotische Wirkstoffe, 10. Mitt. N′-Substituierte N-(1-Adamantyl)harnstoffe

Antimycotic Agents, X: N′-Substituted N-(1-Adamantyl)ureas By nucleophilic addition of 1-aminoadamantane (1) to isocyanates 2 the N′-substituted N-(1-adamantyl)ureas 3 are obtainable. Amenable to this reaction are aliphatic and alicyclic as well as aromatic isocyanates.     

Untersuchungen an 1,3-Thiazinen, 26. Mitt. Neuartige N-Carbamoyl- und Thiocarbamoyl-2-thioxo-1,3-thiazinderivate

1,3-Thiazines, XXVI: Novel N-Carbamoyl- and Thiocarbamoyl-2-thioxo-1,3-thiazine Derivatives The N-unsubstituted 1,3-thiazine derivatives 1–3 were transformed into the N-carbamoyl- or N-thiocarbamoyl-1,3-thiazine derivatives 5–9 by carbamic acid chlorides or thiocarbamic acid chlorides in the presence of triethylamine or sodium hydride.     

Chirale 3-Aminopropanole, 2. Mitt. N-Alkylierungsprodukte

Chiral 3-Aminopropanols, II: N-Alkylated Products From the racem. and optically active 3-aminopropanols 1a-1d the N-monomethyl compounds 3 are obtained via the urethanes 2 . Methylation of 1a-1d according to Eschweiler-Clarke or reaction with formaldehyde/NaBH₃CN yield the N-dimethyl compounds 4 . With acetone/NaBH₄ 1a-1d react to give the N-isopropyl compounds 6 .     

N-Hydroxy-N-arylacetamides. II: Molecular aspects of ferrihaemoglobin formation by N-hydroxy-N-arylacetamides and arylhydroxylamines in the rat

1. Ferrihaemoglobin(HbFe³⁺) formation in rats after i.p. injection of 6 N-hydroxy-N-arylacetamides has shown that N-hydroxy-4-chloroacetanilide(N-hydroxy-4CIAA) was the most active and N-hydroxy-2-acetylaminofluorene(N-hydroxy-2AAF) the least active compound tested. As N-hydroxy-N-arylacetamides were thought to produce HbFe³⁺ only after enzymic N-deacetylation, the corresponding arylhydroxylamines were also tested for HbFe³⁺-forming activity and were found to be more active, N-hydroxy-4-chloroaniline(N-hydroxy-4CIA) being one of the most active and N-hydroxy-2-aminofluorene(N-hydroxy-2AF) the least active compound tested.

2. N-Hydroxy-4-chloroacetanilide given i.p. to rats more rapidly invaded the blood and produced larger amounts of ferrihaemoglobin than did N-hydroxy-2-acetylaminofluorene, due to differences in their availability in plasma.

3. Injection of 50mg/kg of N-hydroxy-4-chloroacetanilide gave similar concn of HbFe³⁺ and 4-chloronitrosobenzene(4-CINOB) as injections of 8?mg/kg of N-hydroxy-4-chloroaniline, indicating that the arylhydroxylamine, after N-deacetylation, was the active molecule in vivo.

4. The concn of 4-chloronitrosobenzene declined faster than HbFe³⁺ concn. 4-Chloronitrosobenzene therefore is a further example of a ‘hit-and-run’ chemical.

5. Inhibition by the microsomal carboxylesterase inhibitor, bis(4-nitrophenyl)phosphate(BNPP), indicated that ferrihaemoglobin formation by 4-chloroacetanilide, but not by N-hydroxy-4-chloroacetanilide, depends on the enzymic activity of hepatic microsomal carboxylesterases.     

N-Hydroxy-N-arylacetamides. III: Mechanism of haemoglobin oxidation by N-hydroxy-4-chloroacetanilide in erythrocytes in vitro

1. N-Hydroxy-4-chloroacetanilide(N-hydroxy-4ClAA) was the most active, and N-hydroxy-2-acetylaminofluorene(N-hydroxy-2AAF) the least active compound among six N-hydroxy-N-arylacetamides, in forming ferrihaemoglobin(HbFe³⁺) in bovine erythrocytes in the presence of 11 mM glucose.

2. N-Hydroxy-4ClAA oxidized 25 equiv. of HbFe²⁺, both in the presence and absence of glucose or lactate. Therefore, its catalytic properties did not depend on metabolic regeneration by the NADPH- or NADH-dependent erythrocyte reductases.

3. In contrast, N-hydroxy-4-chloroaniline(N-hydroxy-4ClA) oxidized 760 equiv. of HbFe²⁺ in the presence of glucose, but only 81 equiv. of HbFe²⁺ in the presence of lactate. These results indicate that the catalytic activity depended on the metabolic regeneration from 4-chloronitrosobenzene(4-CINOB) by NADPH-dependent erythrocyte reductases.

4. A relationship was established between HbFe³⁺ concn. and the concn. of N-hydroxy-4ClA and 4-CINOB(determined together), 4-chloroacetanilide(4-ClAA) and 4-chloroaniline(4-CIA), indicating co-oxidation of N-hydroxy-4ClAA and oxyhaemoglobin in erythrocytes and partial reduction of the newly formed 4-CINOB to 4-CIA.

5. In rat blood in vitro incubated with N-hydroxy-4CIAA, 4-CINOB concn. increased with increasing HbFe³⁺ concn., indicating that 4-CINOB was formed by co-oxidation of oxyhaemoglobin and N-hydroxy-4CIAA, and not by enzymic N-deacetylation.     

Degradation reactions of oral antidiabetics. 1. Reactions of arylsulfonylurea compounds with carboxylic acid anhydrides

Degradation of Oral Antidiabetics, 1: Reactions of Arylsulfonylureas with Carboxylic Acid Anhydrides The arylsulfonylureas 1a–h were reacted with carboxylic acid anhydrides in pyridine. By acetic anhydride, compounds 1 were cleaved rapidly to the N-(arylsulfonyl)acetamides 2 and N-alkylacetamides 3 . In contrast, phthalic anhydride prompted a slow reaction yielding mixtures of N-(arylsulfonyl)phthalimides 9 , arylsulfonamides 10 and N-alkylphthalimides 11 . The ratio of the products formed depends on the reaction time. In the presence of catalytic amounts of DMAP, only 10 and 11 were obtained. Depending on the structure of compounds 1 , treatment with succinic anhydride led to succinic diamides 17 , arylsulfonamides 10 and N-alkyl-succinimides 18 , or N-(arylsulfonyl)succinimides 19 .     

Metabolism of promethazine in vitro. Identification of N-oxidized products

1. Incubation of promethazine (Ia) and desmethylpromethazine (Ib) with 9000g supernatant fractions of rabbit liver homogenate resulted in formation of N-dealkylated, N-oxygenated and ring-hydroxylated products.

2. The N-oxidation products identified by t.l.c. and mass spectra using synthetic reference products are promethazine-N-oxide (IX) and the nitrone (VIII), which is believed to be formed chemically and metabolically from the metabolite N-hydroxydesmethylpromethazine (VII).     

Prodrugs of Peptides. 11. Chemical and Enzymatic Hydrolysis Kinetics of N-Acyloxymethyl Derivatives of a Peptide-like Bond

Various carboxylic acid esters of the N-hydroxymethyl derivative of N-benzyloxycarbonylglycine benzylamide, used as a peptide-like model, were prepared and their decomposition kinetics studied in aqueous solution and in human plasma solutions. These N-acyloxymethylamide derivatives were found to undergo a facile decomposition by a pH-independent process in the pH range 4–8.5, the half-lives being 1–11hr at 37°C. The cause of this limited stability was suggested to be due to the occurrence of an elimination-addition mechanism involving a reactive N-acyliminium ion intermediate. In alkaline solutions (pH > 10) the derivatives showed a normal ester stability. The ester group in the N-acyloxymethyl derivatives was readily hydrolyzed by plasma enzymes to yield the N-hydroxymethyl amide, which subsequently decomposed to the parent amide. The results obtained suggest that N-acyloxymethylation of a peptide bond may be a useful prodrug approach to obtain derivatives with varying lipophilicities and a ready ability to undergo conversion to the parent peptide in vivo. However, the stability of the derivatives in aqueous solutions is limited.     

H n.m.r. spectrum from the flexible N-terminal segment of Streptomyces subtilisin inhibitor

The ¹H n.m.r. spectrum of Streptomyces subtilisin inhibitor shows a limited number of unusually sharp signals at room temperature. Some of these signals are assigned uniquely to protons of the side chains of the N-terminal segment, Aspl-Ala2-Pro3-Ser4-Ala5-Leu6-Tyr7-based on experiments of spin decoupling, pH titration, and enzymatic cleavage of the protein. Quantitative examination of these signals indicates that the N-terminal end of this protein is heterogeneous in that the protein contains a considerable fraction whose sequence starts with Ala2 rather than with Asp1. The pK_a values for the amino groups of Asp1 and Ala2 exposed at the N-terminus are determined to be 8.9 ± 0.4 and 9.0 ± 0.1, respectively. Furthermore, examination of the line-widths of the methyl proton resonances of Ala2 and Ala5 residues indicates that the N-terminal peptide segment is free and undergoes rapid segmental motions in the order of 10^?9s.     

Imidazolsynthesen, 10. Mitt. Zur selektiven Synthese N-substituierter Imidazol-4-äthanole

Selective Synthesis of N-Substituted Imidazole-4-ethanols The synthesis of N-substituted methoxyethylimidazoles 5 , 6 from aldehydes 1 , 1-hydroxy-4-methoxy-2-butanone ( 2 ), primary amines 3 , and ammonia ( 4 ), using the Weidenhagen cyclisation, yields mixtures in which, according to gc analysis, the 1,4-isomers 5 prevail. Ether cleavage with HI gives the N-substituted imidazole-4-ethanols 8 .     

Untersuchungen an 1,3-Thiazinen, 15. Mitt. Neue Synthese für N-substituierte Tetrahydro-1,3-thiazin-2-thione

1,3-Thiazines, XV: New Synthetic Route to N-Substituted Tetrahydro-1,3-thiazine-2-thiones. A new synthetic route to N-substituted tetrahydro-1,3-thiazine-2-thiones 5 giving good yields for N-aryl compounds is reported. It consists of carbon disulfide cleavage of N,N'-disubstituted 2-iminotetrahydro-1,3-thiazines 3 which leads to 5 and the isothiocyanates 6 .