Oligonucleotide phosphorazolidates — Reagents for chemical ligation

The synthesis has been effected in an aqueous medium of oligonucleotide phosphorazolidates derived from imidazole, 2-methylimidazole, benzimidazole, pyrazole, triazole, and benzotriazole with yields close to quantitative. It has been shown that they are all phosphorylating agents in an aqueous medium and can be used as reagents for the directed complementary template assembly of nucleic acid duplexes (chemical ligation). The most reactive are the imidazole, 2-methylimidazole, and benzotriazole derivatives.     

Heterogeneous catalysts in the alkylation of imidazoles

The reaction of imidazoles with alcohols at 300–400°C was studied in the presence of heterogeneous -Al₂O₃ catalysts and Y zeolites. The major reaction was found to be N-alkylation. This reaction is accompanied by C-alkylation on -Al₂O₃ while the selectivity relative to N-alkylation is close to 100% on zeolite catalysts. The greatest activity with 100% selectivity was found for H zeolite. The alkylation of methanol and ethanol by 2-methylimidazole at 310–320°C gave 1,2-dimethylimidazole in -100% yield and 1-ethyl-2-methylimidazole in 90% yield respectively. The reaction of methanol and imidazole gave 1-methylimidazole in 99% yield. This catalyst displays high stability and capacity for oxidative regeneration.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 624–628, May, 1994. Original article submitted April 20, 1994.     

Bonding properties and electronic structures of glycylglycinato copper(II) complexes. Molecular structure of acetylhistaminegly-cylglycinatocopper(II) dihydrate

Summary Mixed ligand diglycinatocopper(II) complexes of the Cu(glygly)L·nH₂O type, where glygly stands for [NH₂-CH₂ CONCH₂CO₂]^2– and L for imidazole (n = 1.5), N-methylimidazole (n = 1), 2-methylimidazole (n = 2), 4-methylimidazole (n = 2), 4-phenylimidazole (n = 2), N-acetylhistamine (n = 2) and NH₃ (n = 2), were prepared and characterized by elemental analyses, i.r., vis. and e.p.r. spectroscopic measurements. The molecular structure of [Cu(glygly)(achmH)]·2H₂O (achmH = acetylhistamine) was determined using three dimensional XRD data. The structure consists of distorted square planar [Cu(glygly)-(achmH)] units interconnected via the peptide oxygen at the apex to complete a square pyramidal structure, Cu—O-(peptide) 2.477(2) Å. The H₂O molecules, not binding directly to the copper ion, involve in intermolecular hydrogen bonding with the copper units. The dianionic glygly ligand and the imidazole ring bind strongly to the central copper ion with Cu—N(amino) 2.045(6) Å, Cu—N-(peptide) 1.891(5) Å, Cu—O(carboxylate) 2.001(4) Å and Cu—N(imidazole) 1.956(5) Å. The dihedral angle between the imidazole nucleus and the CuN₃O xy plane is 6.0°. Similar structures with a CuN₃O coordination plane are proposed for the imidazole complexes, based on spectroscopic data. The bonding properties of the glygly ligand and the unidentate imidazole ligands are elucidated and discussed with reference to the electronic structures of the complexes deduced from Gaussian analyses.     

Synthesis of phosphamide conjugates of 5"-mononucleotides with carcinine and its analogs

The reactions of histamine, the natural dipeptide carcinine (-Ala-HA), and its analogs with 5"-monodeoxyribonucleotides (dNMP) in the presence of triphenylphosphine, 2,2"-dipyridyl disulfide, and N-methylimidazole were studied. The yield of phosphamide derivatives decreases from 72% to 17% as the length of the linker group between the imidazole ring and the terminal aliphatic amino group is increased. Hydrolytic stability of the resulting conjugates was examined. The stability of the bonds in the —O—P(O)₂—NH— group linking the nucleotide and peptide portions of the conjugate depends on the nature of the heterocyclic base of the nucleotide and decreases in the series dTMP > dCMP > dAMP.     

A chemical study of plants of the Mongolian flora lariside — A new scopoletin glycoside fromSalsola laricifolia

A new coumarin glycoside lariside — C₂₁H₂₆O₁₃, mp 155–156°C (from methanol) — has been isolated from the epigeal part ofSalsola laricifolia Turcz. et Litw. On the basis of acid hydrolysis and spectral characteristics the structure of lariside has been established as 7-[O--D-apiofuranosyl-(1 2)--D-glucopyranosyloxy]-6-methoxy-2H-1-benzopyran-2-one.Institute of Chemistry, Academy of Sciences of the Mongolian Peoples' Republic, Ultan-Bator. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 288–291, May–June, 1986.     

Unusual cleavage of phenacyl-substituted benzimidazolium salts. Synthesis of 1,4-diarylimidazoles

The action of ammonium acetate in acetic acid on 1-alkyl(aralkyl)-3-phenacylbenzimidazolium bromides leads, in addition to the formation of a new imidazole ring, to cleavage of the benzimidazole fragment of the molecule at the 1,2 bond to give 1-alkyl(aralkyl)aminoaryl-4-arylimidazoles. 1,2-Dimethyl-3-(p-nitrophenacyl)benzimidazolium bromide is converted under similar conditions to the corresponding 2-methylimidazole. 4,4-Dimethyl-2,2-bis(p-nitrophenyl)-1,1-dipyrrolo[1,2-a]benzimidazole was isolated as a side product of this reaction.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 388–392, March, 1982.     

The influence of pentaamminerhodium(III) on the1H n.m.r. spectra and pyrrole pKas of coordinated imidazoles and pyrazoles

Summary The following [(NH₃)₅RhLH]Cl₃ salts were preparedvia the [(NH₃)₅Rh(O₃SCF₃)](O₃SCF₃)₂ synthetic route; LH=1-methylimidazole (1CH₃imH), 2-methylimidazole (2CH₃imH), 4-methylimidazole (4CH₃imH), 5-methylimidazole(5CH₃imH), and pyrazole (pyzH). pK_a's at 25.0°C were determined for [(NH₃)₅RhLH]³⁺ complexes as follows: 2CH₃imH, 10.4±0.1; 5CH₃imH/4CH₃imH isomer mixture, 10.3±0.1; pyzH, 6.54±0.05. The influence on the pK_a's of imidazoles is dominated by withdrawal of the rhodium(III) centre and may be compensated by the presence of ring methylation by only 0.5log units for cobalt(III) and rhodium(III) derivatives, compared to 1.3 units for the -withdrawing ruthenium(III) centre. In the case of the -acceptor pyrazole ring, [(NH₃)₅Rh]³⁺ is observed to serve as a slight -donor and raises the pK_a above the cobalt(III) analogue. The¹H n.m.r. spectra of [(NH₃)₅RhLH]³⁺ complexes of the substituted imidazoles and pyrazole exhibit a deshielding order. C–2H>C–5H>C–4H for imidazoles and C–3H>C–5H>C–4H for pyrazole, as do their cobalt(III) analogues. The magnitude of values (=_{free L}-_complex) are virtually the same as in the cobalt(III) systems which shows that TIP influences are unimportant compared to ring rehybridization in estabilishing chemical shifts for both the cobalt(III) and rhodium(III) complexes. The imidazolato and pyrazolato complexes exhibit resonances upfield of the respective substituted imidazole or pyrazole complex in keeping with more negative charge on the rings; the influence is largest at C–2H of imidazolates and C–3H of pyrazolate.     

Ternary complexes of copper(II), nickel(II) and zinc(II) with nitrilotriacetic acid as a primary ligand and some phenolic acids as secondary ligands

Summary The formation of ternary complexes of the MAL^3– type [where M = Cu^II, Ni^II and Zn^II ; A = nitrilotriacetic acid (NTA); L = 1-hydroxy-2-naphthoic acid (1,2 HNA) and 2-hydroxy-1-naphthoic acid (2,1 HNA)] have been studied potentiometrically in 50% v/v aqueous — ethanol (25° and µ = 0.1). Under identical conditions the binary complexes of the 1,2- and 2,1-HNA ligands have also been examined. The values of mixed ligand formation constants K_MAL have been found to be lower than K_ML (first step formation constant of binary complexes) and even less than (second step formation constant of binary complexes).     

Triterpene glycosides of Hedera taurica. III. Structures of hederosides A3, B,E2 and F from the berries of Crimean ivy

Four triterpene glycosides — hederoside A₃, B, E₂, and F — have been isolated from the berries ofHedera taurica Carr. (Crimean ivy), family Araliaceae. On the basis of the results of acid hydrolysis and physiochemical methods of investigation the following structures have been suggested: A₃ — 3-O-(-L-arabinopyranosyl)hederagenin; B — 3-O-(-D-glucopyranosyl)hederagenin; E₂ — 3-O-[O--D-glucopyranosyl-(1 2)--D-glucopyranosyl]oleanolic acid; and F — 3-O-[O--D-glucopyranosyl-(1 2)--D-glucopuranosyl]hederagenin. Hederoside E₂ is a new glycoside of oleanolic aid.M. V. Frunze Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 721–726, September–October, 1988.     

Kinetics and mechanism of hydrolysis ofcis-bis(ethylenediamine)imidazole(salicylato)cobalt(III) ion

Summary The kinetics of aquation and base hydrolysis reactions ofcis-[(en)₂Co(imH)O₂CC₆H₄OH-o-o]²⁺ (imH = imidazole) have been investigated in a medium of 1.0 M ionic strength, In the 0,1–1,0 M [H⁺] range (60–70°) aquation proceedsvia spontaneous and acid catalysed paths . In the 0,05–1.0 M [OH^–] range (30–40°), the complex exists predominantly as the bis-deprotonated species,cis-[(en)₂Co(im)O₂CC₆H₄O-o], and the pseudo-first-order rate constant fits the relationship k_obs = k_b + k_b° [OH^–] satisfactorily. The labilizing action of coordinated imidazolate anion(im^–) on the cobalt(III)-bound salicylate is 10³ times stronger than that of imidazole. The mechanism is essentially I_d in the aquation paths and SN₁cb (Co-O bond fission) in the alkali independent and dependent paths respectively.