Reactions of β-alkoxyvinyl trihalogenomethyl ketones with triethyl phosphite

The Perkow reaction of triethyl phosphite and β-alkoxyvinyl trihalogenomethyl ketones, which have common acyclic or cyclic structural fragment: -O-CC-C(O)CX₂Cl, yielded dienyl phosphates: -O-CC-C[OP(O)(OEt)₂]CX₂ where X = F or Cl, whereas γ-bromo-β-methoxy-α,β-unsaturated trifluoromethyl ketone CF₃C(O)CHC(OMe)CH₂Br gave diene CF₃C[OP(O)(OEt)₂]CH-C(OMe)CH₂.     

Diastereoselective hydroformylation of Δ4-steroids with rhodium–phosphite catalysts

The hydroformylation of two steroidal substrates, namely 17β-acetoxyandrost-4-ene 1 and 3β,17β-diacetoxyandrost-4-ene 2, with a rhodium tris(O-tert-butylphenyl)phosphite catalyst was investigated. In both cases, the major reaction product was 4β-formyl-17β-acetoxy-5β-androstane 3, which was isolated and characterized by X-ray diffraction and NMR techniques. This reaction is the first example of catalytic carbonylation to the β face of a steroid backbone. The effect of reaction temperature, the pressure at which the reaction was completed and the ligand:Rh ratio on the regio- and stereoselectivity of the reaction is also discussed.     

Study on the α-Thiocarbonylthioformamide Ⅲ——Reaction with trimethyl phosphite

α-Thiocarbonylthioformamide is a stable and almost unexplored class of compounds¹ which attracts us to study their properties and reactions. According to literature three-valenced phosphorus compound is easy to react with thiirane² and thiocarbonate³ to form C=C double bond. So we want to explore the reaction of α-thiocarbonylthioformamide with three-valenced phosphorus compound. In initial experiment, we explored the reaction of α-thiobenzoylthioformmorpholine (1a) with trimethyl phosphite in dry diethyl ether at room temperature.     

Large scale synthesis of oligoribonucleotides on PEG by the phosphite triester approach

Large scale synthesis of oligoribonucleotides has been successfully performed on PEG support by the phosphoramidite approach using t-butyldimethylsilyl to protect the 2'-hydroxyl group of ribonucleoside. By means of this procedure, the dodecamer r(AGUGGUCUUUGU) was synthesized in 98.1% average coupling yield, and 55 mg pure product was obtained from one gram of functionalized PEG.     

Reaction of trifluoromethylated β-alkoxyenones with tris(trimethylsilyl) phosphite: A temperature influence on regioselectivity

The interaction of tris(trimethylsilyl) phosphite (TMSO)₃P and E-trifluoromethyl-β-alkoxyenones CF₃C(O)CHCHOEt and CF₃C(O)CHC(OMe)Me yielded mixtures of E-1,2- and Z-1,4-adducts, CF₃C(OTMS)[P(O)(OTMS)₂]CCH(OAlk)R 2 and CF₃(OTMS)CCHCR(OAlk)[P(O)(OTMS)₂] 3 where R and Alk = H and Me, or both Me. Conversion of these 1,2-adducts to 1,4-isomers was effected by increased temperature or by exposure to more tris(trimethylsilyl) phosphite. Acid hydrolysis of 2b (R and Alk = Me) gave ketophosphonic acid CF₃C(OH)[P(O)(OH)₂]CH₂COMe in 88% yield, whereas hydrolysis of 2a (R = H and Alk = Et) with KOH in methanol gave CF₃C(OH)[P(O)(OK)₂]CHCHOEt in 37% yield. Acid hydrolysis of 3a (R = H and Alk = Et) and 3b (R and Alk = Me) gave phosphonic acid CF₃C(OH)₂CHCHP(O)(OH)₂ in 82% yield and trifluoromethylated 1,2λ⁵σ⁴-oxaphosphol-3-en.     

The use of new chiral phosphite and amidophosphite ligands in the Rh-catalyzed hydrogenation of dehydro-??-amino acid derivatives

New chiral phosphite-type ligands were synthesized. The tests of these ligands in the asymmetric Rh-catalyzed hydrogenation of N-acetyl derivatives of dehydro-??-amino acid esters showed their high enantioselectivity (up to 75% ee). The reaction of nucleophilic addition of phthalimide to disubstituted alkynes offering access to esters of N-phthaloyldehydro-??-amino acids was discovered. Higher conversion and enantioselectivity in the hydrogenation of N-acetyl and N-phtaloyl derivatives of dehydro-??-amino acids were observed in fluorinated alcohols as compared to common organic solvents.     

Direct coupling of arenes and iodoarenes catalyzed by a rhodium complex with a strongly π-accepting phosphite ligand

A new rhodium-based catalytic system for the direct C-H coupling of arenes and iodoarenes that shows high activity with reasonably broad scope was developed. Under the catalytic influence of RhCl(CO){P[OCH(CF₃)₂]₃}₂ and Ag₂CO₃, the direct C-H arylation of heteroarenes and arenes took place with iodoarenes to afford a range of biaryls in good to excellent yields with high regioselectivity. Thiophenes, furans, pyrroles, indoles, and alkoxybenzenes are applicable to this arylation protocol.     

Study of the Inclusion Complexes of β-Cyclodextrin with the Sodium Salt of Trisulfonated Triphenylphosphine

The formation of inclusion complexesbetween the sodium salt of trisulfonatedtriphenylphosphine and -cyclodextrin has beeninvestigated at two temperatures by high field nuclearmagnetic resonance, electrospray mass and UV-visspectroscopies. At 268 K, titration experiments andJob's method suggest that the major species insolution is a 1 : 1 inclusion complex. The moleculargeometry of this inclusion complex was studied usingthe ROESY NMR technique complemented by molecularmodelling. All these methods converged towards thestructure attained by inserting one aromatic ring intothe hydrophobic cavity of the host from the side ofthe secondary hydroxyls. At 298 K, a higher proportionof 2 : 1 and 3 : 1 complexes induces strong alterations ofthe NMR signals, preventing an easy and reliabledetermination of association constants. Nevertheless,an apparent association constant can be determinedfrom UV-vis data by assuming a 1 : 1 equilibrium. Thegeometry of the 2 : 1 and 3 : 1 complexes is also brieflydiscussed from ROESY NMR experiments.     

Study of the Supramolecular Inclusion of β-Cyclodextrin with Andrographolide

An inclusion complex of -cyclodextrin with andrographolide (Andro) was prepared by using a convenient new method of microwave irradiation. The structure of the inclusion complex was determined by UV and IR analyses as well as ¹H NMR, ¹³C NMR and two dimensional NOE spectroscopic measurements. The results indicated that the possible stoichiometry of complex formation is 1:1 (guest:host ratio) and the two isomeric 1:1 inclusion complexes are present simultaneously in solution. Thermal studies proved the thermal stability of the inclusion complex.     

Non-isothermal Kinetics of the First-stage Decomposition Reaction of the Complex of Terbium p-Methylbenzoate with 1,10-Phenanthroline

The thermal behavior of Tb₂ (p‐MBA)₆(phen)₂ (p‐MBA=p‐methylbenzoate; phen=1,10‐phenanthroline) in a static air atmosphere was investigated by TG‐DTG, SEM and IR techniques. The thermal decomposition of the Tb₂(p‐MBA)₆(phen)₂ occurred in three consecutive stages at T_P of 354, 457 and 595 °C. By Malek method, RO (n<1) was defined as kinetic model for the first‐step thermal decomposition. The activation energy (E) of this step is 170.21 kJ·mol^‐1, the enthalpy of activation (ΔH^≠) 164.98 kJ·mol^‐1, the Gibbs free energy of activation (ΔG^≠) 145.04 kJ·mol^‐1, the entropy of activation (ΔS^≠) 31.77 J·mol^‐1·K^‐1, and the pre‐exponential factor (A) 10^15.21 s^‐1.     

Synthesis ofβ-carboline with the germatrane portion

The 1-oxo-3,3-dimethyl-6-(-trichlorogermyl)ethyl-1,2,3,4-tetrahydroindolo[2,3-c]pyrylium salt, obtained by the acid-catalyzed acylation of 2-(indol-3-yl)dimedone with -trichlorogermylpropionyl chloride and the subsequent reaction with ammonia and triethanolamine, was converted to the corresponding -carboline with the germatrane portion.L. M. Litvinenko Institute of Physicoorganic Chemistry and Carbon Chemistry, Academy of Sciences (NAN) of the Ukraine, Donetsk 340114. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 671–672, May, 1998.     

Probing and modulating the interactions of the DNAzyme with DNA-functionalized nanoparticles

DNA-functionalized gold nanoparticles are one of the most versatile bionanomaterials for biomedical and clinical diagnosis. Herein, we discovered that the performance of DNAzyme cleaving the substrate is highly related to its length. This intriguing phenomenon only appears at the interfaces of DNAfunctionalized gold nanoparticles. We systematically investigated the causes of this phenomenon. We conjectured that the DNAzyme with extended nucleotides that do not match its substrate strand is vulne...     

Exact solution of the Schrödinger equation with a new expansion of anharmonic potential with the use of the supersymmetric quantum mechanics and factorization method

The study involves finding exact eigenvalues of the radial Schrödinger equation for new expansion of the anharmonic potential energy function. All analytical calculations employ the mathematical formalism of the supersymmetric quantum mechanics. The novelty of this study is underlined by the fact that for the first time the recurrence formulas for rovibrational bound energy levels have been derived employing factorization method and algebraic approach. The ground state and the excited states have been determined by means of the hierarchy of the isospectral Hamiltonians. The Riccati nonlinear differential equation with superpotentials has been solved analytically. It has been shown that exact solutions exist when the potential and superpotential parameters satisfy certain supersymmetric constraints. The results obtained can be utilized both in computations of quantum chemistry and theoretical spectroscopy of diatomic molecules.     

On the probable mechanism of the complex formation reaction of metal salts with the β-substituted corroles

The kinetics of the complex formation reaction of the β-hexamethyldiethylcorrole, [H₃(β-Me₆Et₂)Cor], with zinc and cobalt acetates and with zinc acetylacetonate in DMF was studied. The rate of the complexation process between H₃(β-Me₆Et₂)Cor and Zn(OAc)₂ was shown to decrease in the following series of the solvents as DMF < AN < benzene and to suggest elevated chemical activity of the NH bonds in a molecule of corrole. The destruction of β-octaalkylcorrole in the basic solvents (DMF and DMSO) was discovered for the first time, and the kinetic parameters of this process were determined. With account for the structural distinctions between corroles H₃Cor and porphyrins H₂P, the probable mechanism of their reactions with metal salts was discussed and the transition state structure, which noticeably differ from the analogous reactions with porphyrins in the formation of the [H₃Cor · Zn(OAc)₂(Solv) _n?3] intermediate.     

Electrochemical Studies of the Recognition Interaction of Rhodamine B with DNA

The recognition interaction of rhodamine B (RB) with DNA was studied in pH 7.5 Britton-Robinson (B-R) buffer solution by electrochemical techniques. An irreversible oxidation peak at glassy carbon electrode was obtained at 0.92V (vs. SCE). After the addition of DNA into the RB solution, the peak current of RB decreased apparently without the shift of peak potential. The electrochemical parameters such as the charge transfer coefficient α and the electrode reaction standard rate constant ks of RB in the absence and presence of DNA were determined, which did not change, indicating that a non-electroactive complex was formed, so the concentration of RB in the solution decreased and the peak current decreased correspondingly.     

improvement of the Specificity of Surface Plasmon Resonance with BSA-modified Chip

Recently, surface plasmon resonance (SPR) become more and more popular without the need of the label technology1-3. However, sometimes, a number of experimental artifacts complicate the final biosensor analysis4-7. The utilization of a reference surface c…