Sepharose 4B-DNP-hexamethylenediamine as a sorbent for the chromatography of carboxylic proteinases

Summary 1. The chromatography of the carboxylic proteinases porcine pepsin, aspergillopepsin A, and chymosin on the hydrophobic sorbent Sepharose 4B-DNP-hexamethylenediamine has been studied. It has been shown that the nature of the binding of the proteinases with the sorbent depends on the pH.2. A shortening of the length of the carbohydrate chain of the ligand by four methylene units substantially weakens the interaction of pepsin with the sorbent.3. With chymotrypsin and pepsin as examples, the possibility has been shown of using ionic effects for separating these enzymes.M. V. Lomonosov Moscow State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 191–199, March–April, 1979.     

Stereocontrolled synthesis of (+)- and (−)-iridomyrmecin from citronellene enantiomers

Natural (+)-iridomyrmecin and its unnatural enantiomer (−)-iridomyrmecin were synthesized by intramolecular [3+2] dipolar cycloaddition of silyl nitronates that had been generated from the nitro derivatives of (+)- and (−)-citronellenes, respectively. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1683–1687, September, 1997.     

A dimeric constrained‐geometry titanium complex linked by double Ti–CH2–Al–CH2 heterocycles

In the structure of bis({N‐[di­methyl(1η⁵‐2,3,4,6‐tetra­methyl­in­den­yl)­silyl]­cyclo­hexyl­amido‐1κN}(methyl‐3κC)‐di‐μ₃‐methyl­ene‐1:2:3κ³C;1:3:3′κ³C‐tris(pentafluorophenyl‐2κC)titanium) benzene disolvate, [Me₂Si(η⁵‐2,3,4,6‐Me₄C₉H₂)(C₆H₁₁N)]Ti[(μ₃‐CH₂)Al(C₆F₅)₃][AlMe(μ₃‐CH₂)]₂ or [Ti₂(C₂₁H₇AlF₁₅)₂(C₂₁H₃₁NSi)₂]·2C₆D₆, the dimer is located on an inversion center, and the two Ti centers are linked by double Ti(μ₃‐CH₂)Al(C₆F₅)₃AlMe(μ₃‐CH₂) heterocycles. The electron‐deficient Ti centers are further stabilized by two α‐agostic interactions between Ti and one H atom of each bridging methyl­ene group.     

Polymerization of MMA by oscillating zirconocene catalysts, diastereomeric zirconocene mixtures, and diastereospecific metallocene pairs

Characteristics of methyl methacrylate (MMA) polymerization using oscillating zirconocene catalysts, (2-Ph-Ind)₂ZrX₂ (X = Cl, 1; X = Me, 2), mixtures of rac- and meso-zirconocene diastereomers, (SBI)ZrMe₂ [3, SBI = Me₂Si(Ind)₂] and (EBI)ZrMe₂ [4, EBI = C₂H₄(Ind)₂], as well as diastereospecific metallocene pairs, rac-4/Cp₂ZrMe₂ (5) and rac-4/CGCTiMe₂ [6, CGC = Me₂Si(Me₄C₅)(t-BuN)], are reported. MMA polymerization using the chloride catalyst precursor 1 activated with a large excess of the modified methyl aluminoxane is sluggish, uncontrolled, and produces atactic PMMA. On the other hand, the polymerization by a 2/1 ratio of 2/B(C₆F₅)₃ or 2/Ph₃CB(C₆F₅)₄ is controlled and produces syndiotactic PMMA. Mixtures of diastereomeric ansa-zirconocenes 3 or 4 containing various rac/meso ratios, when activated with B(C₆F₅)₃, yield bimodal PMMA; this behavior is attributed to the meso-diastereomer that, in its pure form, affords bimodal, syndio-rich atactic PMMA. For MMA polymerization using diastereospecific metallocene pairs, rac-4/5 and rac-4/6, the isospecific catalyst site dominates the polymerization events under the conditions employed in this study, and the aspecific and syndiospecific sites are largely nonproductive, thereby forming only highly isotactic PMMA.     

Calculation of the viscosity of binary liquids at various temperatures using Jouyban-Acree model

Applicability of the Jouyban-Acree model for calculating absolute viscosity of binary liquid mixtures with respect to temperature and mixture composition is proposed. The correlation ability of the model is evaluated by employing viscosity data of 143 various aqueous and non-aqueous liquid mixtures at various temperatures collected from the literature. The results show that the model is able to correlate the data with an overall percentage deviation (PD) of 1.9+/-2.5%. In order to test the prediction capability of the model, three experimental viscosities from the highest and lowest temperatures along with the viscosities of neat liquids at all temperatures have been employed to train the model, then the viscosity values at other mixture compositions and temperatures were predicted and the overall PD obtained is 2.6+/-4.0%.     

The structures of 5-methyl-5-phenyl-5H-dibenzo[b,f] silepin and its saturated analog

The structures of 5-methyl-5-phenyl-5H-dibenzo[b,f] silepin (I) and 5-methyl- 5-phenyl-1O,11-dihydro-5H-dibenzo [b,f] silepin (II) have been determined from three-dimensional X-ray data collected by counter methods. I crystallizes in the orthorhombic space group Pnam with a 7.596(3), b 18.102(5) and c 12.190(2) Å; observed and calculated densities (Z = 4) are 1.17 and 1.18 g cm^?3, respectively. II crystallizes in the monoclinic space group $\text{P}\text{2}{}_1\text{c}$ with a 11.115(3), b 7.920(3), c 20.765(5) Å and β 111.71(2)°; observed and calculated densities (Z = 4) are 1.17 g cm^?3. Anisotropic refinement of nonhydrogen atoms, with hydrogen atoms included at fixed ideal locations, gave conventional R-factors of 4.5% (I) and 5.0% (II). Compound I exhibits the boat conformation for the tricyclic framework and is located on a crystallographically required mirror plane. Com- pound II has the expected folded boat conformation. The torsion angle about the 10,11-bond is 0.0° for I, a crystallographic symmetry requirement, and 89.9° for II. Mean SiC bond distances are 1.863 Å(I) and 1.875 Å(II). The dihedral angles between the planar benzo groups are 129.7° (I) and 137.2° (II); introduc- tion of unsaturation at the 10,11-position decreases the dihedral angle in the tri- cyclic system, i.e., the tricyclic system is more bent.     

Syntheses based on dimethylpyrazoles. 9. Synthesis and spectral peculiarities of isomeric pyrazolo[3′,4′-5,6]- and-[5′,4′-5,6]-pyrimido[1,2-b]benzo[d,e]isoquinoline-4,12-diones

2-Methyl-2,4,12,13H-pyrazolo[3,4-5,6]pyrimido[1,2-b]benzo[d,e]isoquinoline-4,12-dione and its 8-nitro- and 8-amino-substituted derivatives were obtained starting from 4-amino-3-carbamoyl-1-methylpyrazole and naphthalic and 4-nitronaphthalic anhydrides. The spectral properties of the synthesized compounds were studied.See [1] for Communication 8.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 237–241, February, 1990.     

Effect of a Nickel Bipyridyl Complex on the Reduction of Organic Halides

Indirect reduction of 1-phenylethylbromide (I) and 1-(4-isobutylphenyl)ethylchloride (II) in a carbon dioxide atmosphere containing tris(2,2-bipyridyl)nickel tetrafluoroborate (BPN) is studied. In the reactions the BPN complex exhibits properties of a one-electron mediator and catalyzes radical generation from aryl halides, which mostly undergo dimerization. Electroreduction of I and II in the presence of -cyclodextrin and BPN yields biaryls with a low enanthioselectivity (1.5%), which may indicate generation of a small amount of inclusion complexes and dimerization of intermediate radicals in the hydrophobic cavity of -cyclodextrin.     

Blue-shifted hydrogen-bonded complexes. II. CH3F(HF)1 n 3 and CH2F2(HF)1 n 3

The equilibrium structures, binding energies, and vibrational spectra of the clusters CH₃F(HF)_{1 n 3} and CH₂F₂(HF)_{1 n 3} have been investigated with the aid of large-scale ab initio calculations performed at the Møller–Plesset second-order level. In all complexes, a strong C–FH–F halogen–hydrogen bond is formed. For the cases n = 2 and n = 3, blue-shifting C–HF–H hydrogen bonds are formed additionally. Blue shifts are, however, encountered for all C–H stretching vibrations of the fluoromethanes in all complexes, whether they take part in a hydrogen bond or not, in particular also for n = 1. For the case n = 3, blue shifts of the ν(C–H) stretching vibrational modes larger than 50 cm⁻¹ are predicted. As with the previously treated case of CHF₃(HF)_{1 n 3} complexes (A. Karpfen, E. S. Kryachko, J. Phys. Chem. A 107 (2003) 9724), the typical blue-shifting properties are to a large degree determined by the presence of a strong C–FH–F halogen–hydrogen bond. Therefore, the term blue-shifted appears more appropriate for this class of complexes. Stretching the C–F bond of a fluoromethane by forming a halogen–hydrogen bond causes a shortening of all C–H bonds. The shortening of the C–H bonds is proportional to the stretching of the C–F bond.