High-performance liquid chromatography of xanthines. Effects of N-methyl and C-8 hydroxyl substitution on the retention times

The capacity factors of 26 xanthine derivatives were measured by reversed-phase high-performance liquid chromatography. N-Methyl substitution increased the capacity factor and the related lipid solubility. The descending order of the increase in capacity factor by the N-methyl group is: N-1 methyl greater than N-3 methyl greater than N-7 methyl greater than N-9 methyl. C-8 hydroxylation reduces the capacity factor in the xanthines. The reduction factor is 3.34 in xanthines with N-3 methyl substitution, 2.41 in xanthines with N-1 and/or N-7 methyl substitution and 1.68 in xanthines with N-9 methyl substitution.     

Metal-catalyzed reaction of N-(2-indolyl)methyl, N-bis(trimethylsilyl)methyl diazoamides: an entry into the beta-carboline ring system

The intramolecular metal-catalyzed reaction of N-(2-indolyl)methyl, N-bis(TMS)methyl diazoamides proceeds with high conformational control and chemoselectivity to give cyclopropyl derivatives, which rearrange to beta-carboline products.     

Determination of methyl 13C-15N dipolar couplings in peptides and proteins by three-dimensional and four-dimensional magic-angle spinning solid-state NMR spectroscopy

We describe three- and four-dimensional semiconstant-time transferred echo double resonance (SCT-TEDOR) magic-angle spinning solid-state nuclear magnetic resonance (NMR) experiments for the simultaneous measurement of multiple long-range (15)N-(13)C(methyl) dipolar couplings in uniformly (13)C, (15)N-enriched peptides and proteins with high resolution and sensitivity. The methods take advantage of (13)C spin topologies characteristic of the side-chain methyl groups in amino acids alanine, isoleucine, leucine, methionine, threonine, and valine to encode up to three distinct frequencies ((15)N-(13)C(methyl) dipolar coupling, (15)N chemical shift, and (13)C(methyl) chemical shift) within a single SCT evolution period of initial duration approximately 1(1)J(CC) (where (1)J(CC) approximately 35 Hz, is the one-bond (13)C(methyl)-(13)C J-coupling) while concurrently suppressing the modulation of NMR coherences due to (13)C-(13)C and (15)N-(13)C J-couplings and transverse relaxation. The SCT-TEDOR schemes offer several important advantages over previous methods of this type. First, significant (approximately twofold to threefold) gains in experimental sensitivity can be realized for weak (15)N-(13)C(methyl) dipolar couplings (corresponding to structurally interesting, approximately 3.5 A or longer, distances) and typical (13)C(methyl) transverse relaxation rates. Second, the entire SCT evolution period can be used for (13)C(methyl) and/or (15)N frequency encoding, leading to increased spectral resolution with minimal additional coherence decay. Third, the experiments are inherently "methyl selective," which results in simplified NMR spectra and obviates the use of frequency-selective pulses or other spectral filtering techniques. Finally, the (15)N-(13)C cross-peak buildup trajectories are purely dipolar in nature (i.e., not influenced by J-couplings or relaxation), which enables the straightforward extraction of (15)N-(13)C(methyl) distances using an analytical model. The SCT-TEDOR experiments are demonstrated on a uniformly (13)C, (15)N-labeled peptide, N-acetyl-valine, and a 56 amino acid protein, B1 immunoglobulin-binding domain of protein G (GB1), where the measured (15)N-(13)C(methyl) dipolar couplings provide site-specific information about side-chain dihedral angles and the packing of protein molecules in the crystal lattice.     

Copolymerization and copolymers of brominated phenylmaleimides with some vinyl monomers

The kinetics of the free radical copolymerization in solution of N-(4-bromophenyl)maleimide (MBPMI), N-(2, 4-dibromophenyl)maleimide (DBPMI) and N-(2, 4, 6-tribromophenyl)maleimide (TBPMI) with styrene (St), methyl acrylate (MA), methyl methacrylate (MMA) and acrylonitrile (AN) at low and high conversions were described. Some characteristic properties of the copolymers obtained, particularly their thermal behaviour were also presented.     

Syntheses, emission properties and intramolecular ligand exchange of zinc complexes with ligands belonging to the tmpa family

The zinc complexes [(L1)(2)Zn(MeOH)(2)](OTf)(2), [(L1)ZnCl(2)], [(L2)ZnCl(2)], [(L2)Zn(OTf)(H(2)O)]OTf and [(Me-bispic)ZnCl(2)] of the ligands N-[(2-pyridyl)methyl]-2,2'-dipyridylamine (L1), N-[bis(2-pyridyl)methyl]-2-pyridylamine (L2) and N-methyl-[bis(2-pyridyl)methyl]amine (Me-bispic) were synthesised and characterised. The first copper(I) complexes of the ligands L1 and L2 were also synthesised and structurally characterised. [(L1)ZnCl(2)] showed unexpected fluxional behaviour in solution and revealed an interesting intramolecular ligand exchange mechanism in the coordination sphere of the zinc ion. Furthermore, strong blue emission was observed under UV-light excitation.     

C-H bond activation by unsymmetrical 2-(N-arylimino)pyrrolide Pt complexes: geometric effects on reactivity

Reactions of chloroplatinum methyl complexes with N-(arylimino)pyrrolide anions afford cis and trans neutral platinum methyl complexes. Isomers with methyl trans to the pyrrolide nitrogen activate benzene C-H bonds at 85 degrees C more than 80 times faster than the corresponding cis isomer. In addition, reactions of platinum dimethyl complexes with N-(arylimino)pyrroles (Ar = 4-substituted phenyl) in C6D6 at ambient temperature give unlabeled methane and cis methyl complex containing heavily deuterated Pt-Me. In contrast, bulky aryl substituents give methane isotopomers and trans-Pt-Ph product. The origins of these observations are discussed.     

Anthracene derivatives of benzo[f]quinoline. Synthesis,spectra, and luminescence

By condensation of 9-[N-(2-naphthyl)formimidoyl]anthracene with methyl ketones under conditions of acid catalysis, 1-R-3-(9-anthryl)benzo[f]quinolines have been obtained. The byproducts of the reaction have been identified: 1-R-3-(9-anthyl)-2-propen-1-ones and N-[1-(p-aminophenyl)-3-(9-anthryl)-2-propen-1-ylidene]-2-naphthylamines. The spectral and luminenscence properties of these compounds have been examined critically.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1536–1541, November, 1985.     

Reactions of aromatic and heteroaromatic compounds carrying electron-acceptor substituents. 26. Acylaminomethylation of 2-acylthiophenes, 2-thiophenecarboxylic acid,and its esters

The reaction of 2-thiophene aldehyde, 2-acetylthiophene, 2-thiophene carboxylic acid, and its methyl ester with N-(hydroxymethyl)chloroacetamide in concentrated sulfuric acid yields a mixture of 4- and 5-(N-chloroacetylamino) methyl derivatives, the former being preferred.For Communication 25, see [1].Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 793–797, June, 1986.     

Evaluation op some cellulosic derivatives as carriers for different drugs

Three cellulosic derivatives, namely xanthan, (chlorocarbonyl methyl) cellulose and N-(4-carboxyphenyl)carbamoyl methyl cellulose were used as support in coupling different drugs. Pilocarpine and neomycine were ionically coupled on xanthan; nalidixic acid, metronidazole and cephalosporine C were covalently coupled on (chlorocarbonyl methyl) cellulose, xanthan and N-(4-carboxyphenyl)carbamoyl methyl cellulose, in the latter case dicyclohexylcarbodiimide being used as activator. The influence of some factors on coupling efficiency was followed: drug/support ratio, volume of the solvent, reaction duration, activator/support ratio. The in vitro and in vivo tests proved the biological activity of the newly obtained macromolecular drugs.     

Mononuclear Schiff base boron halides: synthesis, characterization, and dealkylation of trimethyl phosphate

A series of mononuclear boron halides of the type LBX(2) [LH = N-phenyl-3,5-di-tert-butylsalicylaldimine, X = Cl (2), Br (3)] and LBX [LH2 = N-(2-hydroxyphenyl)-3,5-di-tert-butylsalicylaldimine, X = Cl (7), Br (8); LH2 = N-(2-hydroxyethyl)-3,5-di-tert-butylsalicylaldimine, X = Cl (9), Br (10); and LH2 = N-(3-hydroxypropyl)-3,5-di-tert-butylsalicylaldimine, X = Cl (11), Br (12)] were synthesized from their borate precursors LB(OMe)2 (1) (LH = N-phenyl-3,5-di-tert-butylsalicylaldimine) and LB(OMe) [LH2 = N-(2-hydroxyphenyl)-3,5-di-tert-butylsalicylaldimine (4), N-(2-hydroxyethyl)-3,5-di-tert-butylsalicylaldimine (5), N-(3-hydroxypropyl)-3,5-di-tert-butylsalicylaldimine (6)]. The boron halide compounds were air and moisture sensitive, and upon hydrolysis, compound 7 resulted in the oxo-bridged compound 13 that contained two seven-membered boron heterocycles. The boron halide compounds dealkylated trimethyl phosphate in stoichiometric reactions to produce methyl halide and unidentified phosphate materials. Compounds 8 and 12 were found to be the most effective dealkylating agents. On reaction with tert-butyl diphenyl phosphinate, compound 8 produced a unique boron phosphinate compound LB(O)OPPh2 (14) containing a terminal phosphinate group. Compounds 1-14 were characterized by 1H, 13C, 11B, 31P NMR, IR, MS, EA, and MP. Compounds 5, 6, and 11-14 also were characterized by single-crystal X-ray diffraction.     

N-(Benzyloxycarbonyl)-L-vinylglycike Methyl Ester from L-Methionine Methyl Ester Hydrochloride

A reproducible, large scale and practical synthesis of N-(benzyloxycarbonyl)-L-vinylglycine methyl ester starting from L-methionine methyl ester hydrochloride is described.     

Design,Synthesis, Antitubercular and Antibacterial Activities of 1,3,5-Triazinyl Carboxamide Derivatives and In Silico Docking Studies

Russian Journal of General Chemistry - A series of novel N-{2-fluoro-6-[(4,6-dimethoxy-1,3,5-triazin-2-yl)methyl]phenyl} carboxamide derivatives has been synthesized, and their molecular structures...     

Complexing properties of N-[1,1-bis(hydroxymethyl)ethyl]-and N-[tris(hydroxymethyl)methyl]-β-alanine

Russian Chemical Bulletin - Protolytic and complexing properties of N-[1,1-bis(hydroxymethyl)ethyl]- and N-[tris-(hydroxymethyl)methyl]-β-alanine were estimated using the potentiometry. Values...     

Thermal and flammability behaviour of copolymers of N-(2, 4, 6-tribromophenyl)maleimide with some acrylates

The copolymers of N-(2, 4, 6-tribromophenyl)maleimide (TBPMI) with methyl acrylate, methyl methacrylate and acrylonitrile of different composition were prepared by free radical polymerization at low conversion. Their thermal behaviour was established by TGA measurements in helium atmosphere and flammability properties were determined by limiting oxygen index method. The higher TBPMI content in the copolymer led to a higher thermal stability and lower flammability particularly when Sb₂O₃ was used as a synergist.     

Anti-HIV Active Naphthyl Analogues of HEPT and DABO

 5-Isopropyl-6-naphthyl uracil and 5-isopropyl-6-naphthyl-2-thiouracil were alkylated to give N-1-(ethoxymethyl and methylthiomethyl) uracil and S²-cyclohexyl-thiouracil, respectively. 5-Ethyl-6-naphthyl uracil and 5-ethyl-6-naphthyl-2-thiouracil afforded N-1-(ethoxymethyl, methoxy-methyl, methylthiomethyl, acetoxyethoxy methyl and hydroxyethoxy methyl) uracil and S²-((2,2- diethoxyethyl), methoxycarbonylmethyl, ethoxycarbonylpropyl, methylthiomethyl, ethoxymethyl, methyl and cyclohexyl)-thiouracil upon alkylation.     

1,3,3-三甲基-2-亚甲基吲哚啉合成新工艺

报道了一种以N－甲基苯肼和3－甲基－2－丁酮为原料一步合成1，3，3－三甲基－2－亚甲基吲哚啉的新工艺。讨论了影响产品收率的各种因素。该新工艺具有原料易得，工艺路线较短，减少环境污染等特点。     

Anti-HIV Active Naphthyl Analogues of HEPT and DABO

Summary.  5-Isopropyl-6-naphthyl uracil and 5-isopropyl-6-naphthyl-2-thiouracil were alkylated to give N-1-(ethoxymethyl and methylthiomethyl) uracil and S²-cyclohexyl-thiouracil, respectively. 5-Ethyl-6-naphthyl uracil and 5-ethyl-6-naphthyl-2-thiouracil afforded N-1-(ethoxymethyl, methoxy-methyl, methylthiomethyl, acetoxyethoxy methyl and hydroxyethoxy methyl) uracil and S²-((2,2- diethoxyethyl), methoxycarbonylmethyl, ethoxycarbonylpropyl, methylthiomethyl, ethoxymethyl, methyl and cyclohexyl)-thiouracil upon alkylation. Received September 25, 2001. Accepted (revised) December 3, 2001     

Conformational, steric and electronic effects on the site- and chemoselectivity of the metal-catalyzed reaction of N-bis(trimethylsilyl)methyl, N-(2-indolyl)methyl α-diazoamides

The Rh(II)- and Cu(II)-catalyzed reactions of N-bis(trimethylsilyl)methyl, N-(2-indolyl)methyl α-diazoamides are investigated to delineate how conformational, steric and electronic factors influence the site- and chemoselectivity of the metallocarbenoid reaction. The N-bis(trimethylsilyl)methyl (N-BTMSM) group is found to be essential in promoting the metallocarbenoid reaction at the N-(2-indolyl)methyl moiety as well as providing subtle but effective conformational influence about the amide N-C(α) sigma bond in diazoamides carrying an N-C(α) alkoxymethyl side-chain, to afford excellent site- and chemoselectivity. In general, the metal-catalyzed reactions are found to favor metallocarbenoid addition to the indole C(2)-C(3) double bond over C-H insertion to give cyclopropanated products (tetracyclic γ-lactams); however, chemoselectivity is also affected by steric effects, as revealed in the N-[2-(3-methylindolyl)]methyl diazoamides, and to some extent by the nature of the catalyst employed, as seen in the N-C(α)-alkoxymethyl diazoamides. The tetracyclic γ-lactams are found to rearrange to give good to high yields of the tricyclic indole derivatives under the metallocarbenoid reaction conditions or under acidic conditions. The propensity of the tetracyclic γ-lactams to undergo rearrangement is found to be dependent on the nature of the α-substituent on the original diazo carbon and the indole N-substituent.     

On the oxidation of N-methyl and N-benzylpyrimidin-2- and -4-ones by rabbit liver aldehyde oxidase

The presence of a methyl or benzyl group at N-1 or N-3 of 2- and 4-pyrimidone does not affect the site of oxidation by rabbit liver aldehyde oxidase. From all substrates studies only one product viz. the corresponding N-1 or N-3 substituted uracil has been obtained. The maximum rates of oxidation by free enzyme show an optimum in the pH range 6.5–7.8, which is little influenced by the site and the size of the N-substituent. Application of immobilized enzyme in small scale synthesis gives 1- or 3-R-uracils (R = methyl, benzyl) in 43–78% yield.     

The syntheses and thermal rearrangement of some methiodides of s-triazolo[4,3-a]pyridines

It has been shown that the N-methylation, with methyl iodide, of s-triazolo[4,3-a]pyridines affords a mixture of the N-1 and the N-2 methiodides. The N-2 methiodides can be thermally rearranged to the N-1 methiodides. The 8-methyl N-1 methiodides exhibit peri interaction between the two methyl groups. This interaction is reflected in greater stability of the N-2 methiodide vs. the N-1 compound.