3′-(1,2,3-Triazol-1-yl)-2′,3′-dideoxythymidine and 3′-(1,2,3-triazol-1-yl)-2′,3′-dideoxyuridine

Cycloaddition of different acetylenic compounds on the azido function of 3′-azido-2′,3′-dideoxythymidine and 3′-azido-2′,3′-dideoxyuridine afforded products with a 1,2,3-triazol-1-yl substituent in the 3′-position. In contrast with the parent compounds, these triazolyl derivatives had no appreciable activity against human immunodeficiency virus (HIV-1).     

Spectrophotometric determination of cobalt(II) with 2-[di-(2-pyridyl)-methylidenehydrazino]quinoline

A simple, rapid and selective procedure for spectrophotometric determination of cobalt has been developed. Cobalt(II) forms two water-soluble complexes with 2-[di-(2-pyridyl)methylidenehydrazino]quinoline, an orange-yellow complex (lambda(max) 510 nm) in the pH range 2-12 and a pink complex (lambda(max) 530 nm) in 0.1-6M perchloric acid medium. The molar absorptivities for the orange-yellow and pink complexes are 3.65 x 10(4) and 4.1 x 10(4) 1.mole(-1).cm(-1) and Beer's law is obeyed up to 1.84 and 2.0 ppm of cobalt(II) respectively. Cobalt(II) has also been determined in alloys.     

Spectrophotometric determination of cobalt(II) with 2,2'-dipyridyl-2-pyrimidylhydrazone

Some metallochromic indicators are examined for ion-pair formation with alkaloids, cationic surfactants and some pharmaceutical products. Eriochrome red B is recommended for the determination of quinine at pH 3.6 with extraction into chloroform and measurement at 475 nm.     

A dimeric cobalt(II)–suberate complex with 3‐amino­pyridine

The title complex, μ‐octane‐1,8‐dioato‐bis[bis(3‐aminopyridine)chloro(methanol)cobalt(II)], [Co₂(C₈H₁₂O₄)Cl₂(C₅H₆N₂)₄(CH₄O)₂], is located on a crystallographic centre of inversion. The coordination around each of the Co centres is distorted octa­hedral, involving two N, three O and one Cl atom. Discrete dimers are connected in a three‐dimensional arrangement through N—H⋯O, N—H⋯Cl and O—H⋯O hydrogen‐bond inter­actions.     

A chloro(2‐pyridinecarboxaldehyde)(2,2′:6′,2′′‐ter­pyridine)­ruthenium(II) complex

The aldehyde moiety in the title complex, chloro(2‐pyridinecarboxaldehyde‐N,O)(2,2′:6′,2′′‐terpyridine‐κ³N)ruthenium(II)–chloro­(2‐pyridine­carboxyl­ic acid‐N,O)(2,2′:6′,2′′‐ter­pyridine‐κ³N)­ruthenium(II)–perchlorate–chloro­form–water (1.8/0.2/2/1/1), [RuCl­(C₆H₅NO)­(C₁₅H₁₁N₃)]_1.8[RuCl­(C₆H₅­NO₂)(C₁₅H₁₁N₃)]_0.2­(ClO₄)₂·­CHCl₃·­H₂O, is a structural model of substrate coordination to a transfer hydrogenation catalyst. The title complex features two independent Ru^II complex cations that display very similar distorted octahedral coordination provided by the three N atoms of the 2,2′:6′,2′′‐ter­pyridine ligand, the N and O atoms of the 2‐pyridine­carbox­aldehyde (pyCHO) ligand and a chloride ligand. One of the cation sites is disordered such that the aldehyde group is replaced by a 20 (1)% contribution from a carboxyl­ic acid group (aldehyde H replaced by carboxyl O—H). Notable dimensions in the non‐disordered complex cation are Ru—N 2.034 (2) Å and Ru—O 2.079 (2) Å to the pyCHO ligand and O—C 1.239 (4) Å for the pyCHO carbonyl group.     

Spectrophotometric determination of cobalt with 1-(2-pyridylazo)-2-naphthol and surfactants

A simple and highly selective spectrophotometric method for the determination of cobalt based upon the rapid reaction with PAN in the presence of surfactants and minute amounts of ammonium persulphate at pH 5.0 is described. The cobalt(III) chelate is made water-soluble by a neutral surfactant. Triton X-100, combined with sodium dodecylbenzene sulphonate (DBS). Iron(III), bismuth, tin(IV) and aluminium are masked with oxalate or citrate. Iron(II) must be absent. The other metal-PAN chelates, except that of nickel, are readily decomposed by EDTA. Up to 150 microg of nickel does not interfere. When larger amounts up to 625 microg are present, the absorbance can be corrected by measurements at two wavelengths. In a strongly acid medium (below pH 0.5) the nickel and other metal chelates are completely and instantaneously decomposed, while the cobalt(III) chelate remains unchanged. When, in place of EDTA, several ml of 6M hydrochloric acid are added after the colour development, nickel in quantities up to 1250 microg can be tolerated. A several hundredfold excess of zinc and manganese does not interfere. At 620 nm Beer's law is obeyed over the cobalt concentration range 0.4-3.2 microg/ml. The precision (95% confidence) is +/- 1.0 microg for 100 microg of cobalt. The molar absorptivity is 1.90 x 10(4) l. mole(-1) .cm(-1).     

Cobalt(II) and cobalt(III) complexes with 4′‐(4‐cyanophenyl)‐2,2′:6′,2′′‐terpyridine

4′‐Cyanophenyl‐2,2′:6′,2′′‐terpyridine (cptpy) was employed as an N,N′,N′′‐tridentate ligand to synthesize the compounds bis[4′‐(4‐cyanophenyl)‐2,2′:6′,2′′‐terpyridine]cobalt(II) bis(tetrafluoridoborate) nitromethane solvate, [Co^II(C₂₂H₁₄N₄)₂](BF₄)₂·CH₃NO₂, (I), and bis[4′‐(4‐cyanophenyl)‐2,2′:6′,2′′‐terpyridine]cobalt(III) tris(tetrafluoridoborate) nitromethane sesquisolvate, [Co^III(C₂₂H₁₄N₄)₂](BF₄)₃·1.5CH₃NO₂, (II). In both complexes, the cobalt ions occupy a distorted octahedral geometry with two cptpy ligands in a meridional configuration. A greater distortion from octahedral geometry is observed in (I), which indicates a different steric consequence of the constrained ligand bite on the Co^II and Co^III ions. The crystal structure of (I) features an interlocked sheet motif, which differs from the one‐dimensional chain packing style present in (II). The lower dimensionality in (II) can be explained by the disturbance caused by the larger number of anions and solvent molecules involved in the crystal structure of (II). All atoms in (I) are on general positions, and the F atoms of one BF₄⁻ anion are disordered. In (II), one B atom is on an inversion center, necessitating disorder of the four attached F atoms, another B atom is on a twofold axis with ordered F atoms, and the C and N atoms of one nitromethane solvent molecule are on a twofold axis, causing disorder of the methyl H atoms. This relatively uncommon study of analogous Co^II and Co^III complexes provides a better understanding of the effects of different oxidation states on coordination geometry and crystal packing.     

Spectrophotometric extractive determination of iodide as tris(2-(phenyliminomethyl)pyridine) Fe(II) iodide

The iodide:tris(2-(phenyliminomethyl)pyridine) Fe(II) extraction system into nitrobenzene has been studied. The same method is proposed for the determination of iodide. The interference of foreign ions is also determined.     

Nucleosides and Nucleotides. Part 13. Synthesis and spectral properties of 1- (3′-O-Phosphoryl-2′-deoxy-β -D-ribofuranosyl)-2(1H)-pyridone-(3′-5′)-1-(2′-deoxy-β-D-ribofuranosyl)-2 (1H)-pyridone

The dinucleoside phosphate Π_dpΠ_d ( 4 ) was synthesized from the monomers 1-(5′-O-monomethoxytrityl - 2′ - deoxy - β - D - ribofuranosyl) - 2 (1 H) - pyridone ((MeOTr) Π_d, 2 ) and 1-(5′-O-phosphoryl-3′-O-acetyl-2′-deoxy-β-D -ribofuranosyl)-(1H)-pyridone (pΠ_d(Ac), 3 ). Its 6.4% hyperchromicity and an analysis of the ¹H-NMR. spectra indicate that the conformation and the base-base interactions in 4 are similar to those in natural pyrimidine dinucleoside phosphates.     

Nucleoside und Nucleotide. Teil 10. Synthese von Thymidylyl-(3′-5′) -thymidylyl-(3′-5′)-1-(2′-desoxy-β-D-ribofuranosyl)-2(1 H)-pyridon

Nucleosides and Nucleotides. Part 10. Synthesis of Thymidylyl-(3′-5′)-thymidylyl-(3′-5′)-1-(2′-deoxy-β-D - ribofuranosyl)-2(1 H)-pyridone The synthesis of 5′-O-monomethoxytritylthymidylyl-(3′-5′)-thymidylyl-(3′-5′)-1-(2′-deoxy-β-D -ribofuranosyl)-2(1H)-pyridone ((MeOTr)T_dpT_dp∏_d, 5 ) and of thymidylyl-(3′-5′)-thymidylyl-(3′-5′)-1-(2′-deoxy-β-D -ribofuranosyl)-2(1 H)-pyridone (T_dpT_dp∏_d, 11 ) by condensing (MeOTr) T_dpT_d ( 3 ) and p∏_d(Ac) ( 4 ) in the presence of DCC in abs. pyridine is described. Condensation of (MeOTr) T_dpT_dp ( 6 ) with Π_d(Ac) ( 7 ) did not yield the desired product 5 because compound 6 formed the 3′-pyrophosphate. The removal of the acetyl- and p-methoxytrityl protecting group was effected by treatment with conc. ammonia solution at room temperature, and acetic acid/pyridine 7 : 3 at 100°, respectively. Enzymatic degradation of the trinucleoside diphosphate 11 with phosphodiesterase I and II yielded T_d, pT_d and p∏_d, T_dp and Π_d, respectively, in correct ratios.     

5-(α-Fluorovinyl)tryptamines and 5-(α-Fluorovinyl)-3-(N-methyl-1′,2′,5′,6′,-tetrahydropyridin-3′- and -4′-yl)indoles—5-(α-Fluorovinyl)tryptamines

5-(α-Fluorovinyl)tryptamines 4a, 4b and 5-(α-fluorovinyl)-3-(N-methyl-1′,2′,5′,6′-tetrahydropyridin-3′- and -4′-yl) indoles 5a, 5b were synthesized using 5-(α-fluorovinyl)indole ( 7 ). The target compounds are bioisosteres of 5-carboxyamido substituted tryptamines and their tetrahydropyridyl analogs.     

Syntheses, structures and photochromism of two novel copper(II) complexes with 1,2-bis(2′-methyl-5′-(2″-pyridyl)-3′-thienyl)perfluorocyclopentene

Two novel Cu(II) complexes with 1,2-bis(2′-methyl-5′-(2″-pyridyl)-3′-thienyl)perfluorocyclopentene (BM-2-PTP) or its closed-form (closed-BM-2-PTP) were synthesized and characterized by X-ray crystallographic analysis. Both complexes are tetra-coordinated to two N atoms from distinct ligands and two Cl atoms from anions, forming 1-D polymeric structures. [Cu(BM-2-PTP)Cl₂] (1) showed typical spectral changes as analogous Ag(I) complexes with the same ligand upon appropriate light stimulus. However, closed-BM-2-PTP displayed different photocyclization from its open-ring form upon irradiation with UV light, indicating the photogenerated closed form turned into two kinds of closed-ring isomers. Furthermore, [Cu(closed-BM-2-PTP)Cl₂] (2) was revealed to contain two conformers by X-ray crystallographic analysis and displayed similarities in photocyclization to its free ligand. The distinct absorptions of the UV spectrum were attributed to the coexistence of two conformers in complex 2, both of which showed effective photoreactivities in the crystalline phase. The photochromic mechanism of complex 2 is tentatively concluded as two conformers displaying independent photoreactions.     

Synthesis of 2-(2′,3′-dihydroxypropyl)-5-amino-2H-1,2,4-thiadiazol-3-one and 3-(2′,3′-dihydroxypropyl)-5-amino-3H-1,3,4-thiadiazol-2-one

The synthesis of two new acyclic nucleoside analogs, 2-(2′,3′-dihydroxypropyl)-5-amino-2H-1,2,4-thiadiazol-3-one (1) and 3-(2′,3′-dihydroxypropyl)-5-amino-3H-1,3,4-thiadiazol-2-one (2), is reported. The first compound, 1, was obtained by reaction of 3-chloro-1,2-propanediol with the sodium salt of 5-amino-2H-1,2,4-thiadiazol-3-one (3) in anhydrous dimethylformamide. Similarly, 5-amino-3H-1,3,4-thiadiazol-2-one (4) reacted with 3-chloro-1,2-propanediol to give 2. The thiadiazole 4 was prepared by condensation-cyclization of hydrazothiodicarbonamide (9).     

Nucleotides. Part XXXV. Synthesis of 3′-deoxyadenylyl-(2′–5′)-3′-deoxyadenyIyl-(2′–ω)-9-(ω-hydroxyalkyl)adenines

Via the phosphotriester approach, new structural analogs of (2′–5′)oligoadenyiates, namely 3′-deoxyadenylyl-(2′–5′)-3′-dcoxyadenylyl-(2′–ω)-9-(ω-hydroxyalkyl)adenines 18 – 21 , have been synthesized (see Scheme) which should preserve biological activity and show higher stability towards phosphodiesterases. The newly synthesized oligonucleotides 18 – 21 have been characterized by ¹H-NMR spectra, TLC, and HPLC analysis.     

Kinetic study of the complex reaction between copper(II) and 2-(2′-hydroxy-3′-methoxyphenyl)benzothiazole

2-(2′-Hydroxy-3′-methoxyphenyl)benzothiazole reacts with copper(II) in an ethanol/water mixture to form an O,S chelate which exhibits the remarkable property of changing the chelation site above a pH of ca. 5.0, to the O,N site. The detailed kinetics of this reaction in an ethanol/water mixture (3:1) at a temperature of 25 °C was investigated using a stopped-flow spectrophotometric technique employing a wavelength of 400 nm. The initial complex, Cu(O,S), is formed via a fast, reversible second-order complex formation step whereupon the formation of the Cu (O,N) follows first order kinetics. The Cu(O,N) complex is, however, unstable towards internal electron exchange and after the reaction is complete, a black polymeric material very slowly precipitates out of solution. Rate and equilibrium constants for the postulated reactions are presented and discussed.