1:1 and 1:2 Inclusion Complexes of Di-tert-butyl l-tartrate with α-Cyclodextrin: A Diffusion Study

The diffusion properties at two overall compositions of a ternary aqueous system containing α-cyclodextrin and a double-functional guest molecule, namely di-tert-butyl l-tartrate, have been studied by means of the Gouy interferometry. The experimental data are interpreted in terms of two independent chemical equilibria involving inclusion compounds. The elements of the diffusion coefficient matrix have been expressed as functions of the two equilibrium constants as well as of the diffusivities of the actual species occurring in solution. The reliability of the diffusion coefficients obtained through the Fujita–Gosting–Revzin procedure is also discussed in terms of its dependence on the composition of solutions used in the Gouy experiments.     

The 1:1 adduct of 2,5-dihydroxy-1,4-benzoquinone with 4,4′-bipyridine

2,5-Di­hydroxy-1,4-benzo­quinone (DHBQ) and 4,4′-bi­pyridine (BPY) crystallize in a 1:1 ratio as a neutral molecular adduct, C₆H₄O₄·C₁₀H₈N₂, in space group C2/c, with half of each mol­ecule in the asymmetric unit. The mol­ecules are linked by a strong O—H⃛N hydrogen bond [O⃛N 2.6323 (15) Å] and a weak C—H⃛O hydrogen bond [C⃛O 3.2082 (17) Å] to form infinite stacks of parallel one-dimensional hydrogen-bonded ribbons. The two rings of the bi­pyridine are twisted at 28.3° with respect to each other, and the benzo­quinone ring is inclined at an angle of 18.3° with respect to the plane of the neighbouring pyridine ring. The 4,4′-bi­pyridine mol­ecule lies on a twofold axis and the benzo­quinone mol­ecule lies across an inversion centre.     

Determination of the anharmonic force constant Ksδδ of the amino group of trifluoroethylamine in 1:1 complexes with bases

The Fermi coupling coefficient W, which measures the intensity of the resonance interaction and is proportional to the anharmonic force constant K_sδδ of the amino group, is measured by two independent methods in 1:1 complexes of trifluoroethylamine with bases in dilute CCl₄ solutions.Values of W from the intensity ratio of Fermi doublet components R, are in good agreement with more precise calculation based on frequencies ν_s, ν_a and 2δ of the protio species (NH₂) and ν_fν_b of the monodeutero species (NHD). There is a large sensitivity of W to the pK_B of the base but there is no appreciable temperature dependence.     

Oligomerization of N-aminodipeptides: to the synthesis of heterogeneous backbone with 1:1 α:α-N-amino aminoacid residue patterns

A large number of N-aminodipeptides compounds have been obtained via a Mitsunobu protocol performed in solution or by solid-phase synthesis. The oligomerization of some of them has been studied in solution or on solid support leading to the formation of 1:1[α:α-N-amino]mers.     

Phosphorylation mapping of laminin α1-chain: Kinases in association with active sites

Laminin­111 is a trimeric glycoprotein of the extracellular matrix (ECM) that holds a significant role in cell adhesion, migration and differentiation. Laminin­111 is the most studied laminin isoform, composed of three chains; α1, β1 and γ1. Phosphorylation is the most common eukaryotic post ­ translational modification and has regulatory effect on protein function. Using bioinformatic tools we computationally predicted all the possible phosphorylation sites on human laminin α1-chain sequence (LAMA1) according to kinases binding motifs. Thus, we predicted, for the first time, the possibly responsible kinases for fifteen of the nineteen already published experimentally observed phosphorylated residues in LAMA1. Searching the literature extensively, we recorded all the known functional sites (active sites) in LAMA1. We combined the experimentally observed and predicted phosphorylated residues as well as the active sites in LAMA1, generating an analytic phosphorylation map of human laminin α1-chain, which is useful for further analysis. Our results indicated fourteen kinases that might be important for the phosphorylation of human laminin α1-chain, out of which three kinases with reported ecto-phosphorylation activity (PKA, PKC and CKII) were suggested to have a more significant role. Six cancer associated-active sites were correlated with kinases, three out which were correlated with only the above ecto ­ kinases.     

Synthesis and crystal structure of a new paramagnetic complex salt of diprotonated dioxocyclam with PtCl 2− 4 and water (1:1:1)

The paramagnetic complex salt of diprotonated dioxocyclam (1,11-dihydro-5,7-dioxo-1,4,8,11tetra-azacyclotetradecane), Pt(II) tetrachloride and water has been synthesized in strongly acidic medium and identified by X-ray structure analysis. The crystals of [(C₁₀H₂₂N₄O₂)²⁺(PtCl₄)^2–]·H₂O are monoclinic, space groupP2₁ c,M _r=585.23,a=9.516(1) Å,b=11.926(1) Å,c=16.622(2) Å,=102.88(2)°,V=1839(1)ų,Z=4,D _x=2.114 g cm^–3, (MoK )=0.70930 Å,=83.1 cm^–1,F(000)=1128,T=292 K,R=0.019 for 2808 observed reflections withI > 3(I). Alternating moieties of diprotonated dioxocyclam and a PtCl _2– ⁴ anion form columns running down the c axis. Water molecules are localized in the intercolumnar space and contribute to the extensive hydrogen bond network. The macrocycle conformation is characterized by two sequences of torsional angles, corresponding to two different subunits. The shorter sequence idealized as (-sc, ap, -ac, + ac, ap, +sc) [sc( ±60°), ac( ±120°), ap(180°)], describing the C pseudosymmetric part of the molecule, is centered on a -CH₂ group between the two peptide O-C-N-H fragments. The opposite C pseudosymmetric subunit has a nearly (-sc, ac, -SC, ap)₂ conformation. Pt is square planar coordinated by four Cl atoms, Pt-Cl_ve = 2.306(8) Å. The shortest Pt ... Pt distance is 7.200(1) Å.     

Ruthenium hydrazone complexes with 1:1 and 1:2 metal–ligand stoichiometry: a comparison of biomolecular interactions and in vitro cytotoxicities

Transition Metal Chemistry - Two ruthenium(II) complexes [RuIICl(PPh3)2(L)] (1) and [RuII(L)2] (2) were synthesized by reacting [RuCl2(PPh3)3] and thiophene-2-carboxylic acid...     

Reaction of Chlorosulfonyl Isocyanate with Benzopinacolones and Benzophenones: Synthesis of Benzopinacolone-2′-Sulfonamides and Benzoisothiazole-1, 1-dioxides

Abstract-Benzopinacolones, 1a-c, reacted with chlorosulfonyl isocyanate (CSI) at 130[ddot]C to yield the benzopinacolone-2′ -sulfonamides, 4a-c. Similarly benzophenones, 5a-d, reacted with CSI to give the benzoisothiazole-1, 1-dioxides, 7a-d.     

Thermodynamic Data for the Formation of 1:1 and 2:1 Complexes of α,ω-Diamino Dihydrochlorides with 18-Crown-6 in Aqueous Solution

Calorimetric titrations are used to study the interactions between the crown ether 18-crown-6 and several α,ω-diamino dihydrochlorides in aqueous solution. These complexes are formed by ion-dipole interactions between the positively charged nitrogen atoms and the oxygen donor atoms of the crown ether. Depending on the experimental conditions, the formation of 1:1 or 2:1 complexes (ligand:diamines) can be studied. The solvation of the ligand and the amines are responsible for the observed thermodynamic values. The number of water molecules released during the reaction were calculated from the determined reaction entropies. Formation of 1:1 complexes distorts the solvation shell around the molecules. As a result, the number of solvent molecules released during the formation of the 2:1 complexes is slightly smaller than the number released from formation of the 1:1 complex. No experimental evidence is observed for the formation of complexes between one crown ether and two protonated amino groups.     

Cold chemistry with ionic partners: quantum features of HeH+(1Σ) with H(1S) at ultralow energies

Quantum reactive calculations are presented for an ion-atom reaction involving the HeH(+)cation and its destruction via a barrierless interaction with H atoms. The range of collision energies considered is that of a cold trap regime (around and below millikelvin) where the ionic partner could be spatially confined. Specific resonant features caused by the interplay of the strong ionic interaction with the very slow partners' dynamics are found and analyzed. Indications are also given on the consequences of the abstraction mechanism that acts for this reaction at low energies.     

Nickel-Catalyzed Aminocarbonylation of Aryl Iodides with 1 atm CO

Reported here is a nickel-catalyzed aminocarbonylation of aromatic iodides with (hetero)aryl anilines and alkyl amines under atmospheric CO pressure. The reaction features with broad substrate scope with excellent functional group tolerance, providing an expedient method for the construction of amide analogues. Notably, amino alcohols can be selectively transformed into the corresponding amides successfully without interfering the hydroxyl group under the current standard conditions.     

Cyclopropanation of 1, 1-Dichloro-4-methyl-1,3-pentadiene with Diazoacetate

DuetoitswideappIicationasakeyintermediateofvariouskindsofeffectivepyrethroids,thesynthesisof3(2,2-dichlorovinyl)-2,2-dimethy(III)hasattractedmuchattentionI1-3J.Severalsyntheticmethodshavebeenreportedandsomehavebeenindustrialized.However-comparedwiththegreatamountofliteratUtreusingothermethodstosynthesizelll.onlyafewworkswerereportedaboutcyclopropanationofl,l-dichloro-4-methyl-l-3-pentadiene(I)withdiazoacetate(II),andtheirchemicaIyieldswererelativel}Io.l'~leventhoughthiskindofreactiOI1wasv…     

Competition and interplay between σ-hole and π-hole interactions: a computational study of 1:1 and 1:2 complexes of nitryl halides (O2NX) with ammonia

Quantum calculations at the MP2/cc-pVTZ, MP2/aug-cc-pVTZ, and CCSD(T)/cc-pVTZ levels have been used to examine 1:1 and 1:2 complexes between O(2)NX (X = Cl, Br, and I) with NH(3). The interaction of the lone pair of the ammonia with the σ-hole and π-hole of O(2)NX molecules have been considered. The 1:1 complexes can easily be differentiated using the stretching frequency of the N-X bond. Thus, those complexes with σ-hole interaction show a blue shift of the N-X bond stretching whereas a red shift is observed in the complexes along the π-hole. The SAPT-DFT methodology has been used to gain insight on the source of the interaction energy. In the 1:2 complexes, the cooperative and diminutive energetic effects have been analyzed using the many-body interaction energies. The nature of the interactions has been characterized with the atoms in molecules (AIM) and natural bond orbital (NBO) methodologies. Stabilization energies of 1:1 and 1:2 complexes including the variation of the zero point vibrational energy (ΔZPVE) are in the ranges 7-26 and 14-46 kJ mol(-1), respectively.     

The cleavage of meso-epoxides with homochiral thiols: synthesis of (+)- and (−)-trans-1-mercaptocyclohexan-2-ol

The synthesis of (+)- and (−)-trans-1-mercaptocyclohexan-2-ol is described. Ring opening of cyclohexene oxide with (−)-4-methoxybenzylnopan-3(R)-thiol 1a followed by oxidation gives two readily separable diastereomeric sulfoxides. These sulfoxides display very different thermal stability but both undergo regio-specific syn-elimination to give cyclohexan-1-ol-2-sulfenic acid that can be reacted in situ with 3,5-dimethylthiophenol to give a mixed disulfide. Reduction of these disulfides with lithium aluminium hydride gives the title compounds in enantiomerically pure form.     

Inclusion of α-phenyl-N-p-methylphenyl Nitrone in β- Cyclodextrin: Formation of 1G : 1H and 1G : 2H Complexes and the Remarkably Fast 1,3-Dipolar Cycloaddition of the 1G : 2H Complex with Olefins in the Solid State

The nitrone is found to be included in the -cyclodextrin cavity in two different stoichiometries viz., 1G : 1H and 1G : 2H – the existence of which is proved by physical methods. The 1G : 2H complex of the nitrone serves as a good potent dipolarophile in the 1,3-dipolar cycloaddition reactions with olefins resulting in rate acceleration and regioselection.     

Features of Reactions of Some 1-Arylaminomethylisatins with Girard’s Reagent T

Depending on the structure of the substituent at the endocyclic nitrogen atom, the reactions of aminomethylisatins with the Girard’s reagent T can proceed both with the elimination of the aminomethyl group and with its retention resulting in the formation of the corresponding positively charged isatin-3-acylhydrazones.     

Condensation of 1-Substituted 5-Aminopyrazoles with β-Dicarbonyl Compounds

Condensation of N-substituted 5-aminopyrazoles with -diketones occurs with the formation of pyrazolo[4,5-b]pyridines. Depending on the conditions, their reaction with -keto acids can give either 6-oxo- or 4-oxopyrazolo[4,5-b]pyridines.