Über die Stereochemie der Hydrogenolyse von N-Benzyl-Bindungen I. Die Hydrogenolyse von Derivaten der 2-Amino-2-phenyl-propionsäure.

The stereochemistry of the hydrogenolysis of benzyl-N bonds was studied using S(+)-2-dimethylamino-2-phenyl-propionic acid (I) and its derivatives, and R(?)-2-anilino-2-phenyl-propionic acid (II). The configuration of I was confirmed, that of II established by ORD. measurements, after transformation of the phenyl into cyclohexyl groups. On a palladium catalyst the hydrogenolysis of I, its methyl and ethyl esters and its amide proceeded with 72 to 99% inversion of configuration, that of II with at least 66% inversion. The ester of the quaternary ammonium derivative of I gave as much inversion as retention (= racemisation).     

Echange d'oxygène lors de la substitution électrophile des phénols

In the bromodesulfonation of sodium 2, 6-dibromophenol-4-sulfonate (I) and similar compounds, the relatively stable quinoloid intermediate II exchanges its carbonyl oxygen with that of H₂¹⁸O by an addition-elimination process. The exchange is slower than the formation of the product III; it is roughly comparable to the exchange velocity of quinones of similar structure. By reversibility of the electrophilic additon step, ¹⁸O is incorporated into the starting phenol I. In electrophilic substitutions with shorter life-time of the quinoloid intermediate, the oxygen exchange is difficult or impossible to observe.     

The Nitrosation of Primary Aliphatic Diazocarbonyl Compounds: Formation of α-carbonyl nitrile oxides. Preliminary communication

Aqueous nitrosation of primary α-carbonyl diazo compounds (ethyl diazoacetate, diazoacetone, diazoacetophenones) yields α-carbonyl nitrile oxides, R? CO? CNO; their formation is demonstrated by 1,3-dipolar addition reactions.     

Optical rotatory dispersion and circular dichroism. LXXV. Circular dichroism of some aryl-amino acids

CD. curves have been recorded for α-aryl-α-amino acids, esters and amides related to α-phenylglycine, α-phenyl-alanine and their N-dimethyl derivatives, and for the corresponding α-cyclohexyl-α-amino acids and esters. Compounds with the (S)-configuration at the single asymmetric carbon atom give strong positive Cotton effects near 220 nm. The conformations of the acids are discussed and compared with those of other α-amino acids.     

Unambiguous Proof for Alcoxycarbonyl-group Migration in Wagner-Meerwein Rearrangements

In HSO₃F/SO₂ClF the β-hydroxy esters Ph-CHOH-CMe₂-COOR ( 1 , R?Me, Et) are doubly protonated, then transformed into the fluorosulfates 7 and (partly) into the fluorides 8. At ?15°, both 7 and 8 undergo a rearrangement, forming derivatives of Me₂C?C(Ph)COOR ( 2 ). By labelling 1 with ¹³C, singly (¹³C(3)) and doubly (¹³C(1,3)), it could be shown that exclusively the ROOC groups undergo a 1,2-shift. Compound 2 is also formed in HSO₃F/SO₂ClF from the isomeric Me₂COH-CHPh-COOR ( 3 ) by elimination, and less easily from the α-hydroxy ester Ph-CMe₂-CHOH-COOR (5) via a phenyl 1,2-shift. Another isomer, Ph-C(OH)Me-CHMe-COOR (4) gives products different from 2 . Using more acidic systems containing SbF₅, the free carbenium ions 13 (Ph-CH⁺-CMe₂-COOR) can be stabilized; they do not form 2 , possibly because of complexation of the ester group with SbF₅. The energy profile and the mechanism of the rearrangement 1 → 2 are discussed.     

Thermal Characterizations of Inorganic and Organometallic Polymers

This review emphasizes the breadth of metallic and metallic-like polymers evaluated as to thermal properties. Techniques usefully applied to particular systems are noted with the aim of suggesting their application to other systems.     

Low-lying energy levels of the FeH molecule

Multireference configuration interaction (MRCI) and complete active space second-order perturbation theory (CASPT2) calculations are performed on Fe₂ and Fe^? ₂. Although it is not possible to definitively identify the ground states of Fe₂ and Fe^? ₂, the calculations suggest that the ground state of Fe^? ₂ in ⁸Σ^? _u derived from 3d¹³4σ² _g4σ² _u and that the states observed in photodetachment are the ⁹Σ^? _g and ⁷Σ^? _g states with a 3d¹³4σ² _g4σ¹ _u occupation, but that the ground state of Fe₂ is ⁷Δ_u(3d¹⁴4σ² _g) and is not observed in the photo-detachment spectra.     

Fibrinogen adsorption onto 316L stainless steel, Nitinol and titanium

Fibrinogen adsorption onto mechanically polished biomedical grade 316L stainless steel (316LSS), nickel titanium alloy (Nitinol) and commercially pure titanium (CpTi) surfaces were studied by measurements of adsorption isotherms and adsorption kinetics using an ex-situ wavelength dispersive spectroscopy technique (WDS). Surface composition, roughness and wettability of these materials were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and water contact angle (WCA) measurements. Adsorption isotherm results showed that surface protein concentration on these materials increased with increasing concentration of fibrinogen in phosphate buffer solution. The fibrinogen adsorption isotherms were modeled by both the monolayer Langmuir isotherm and the multilayer Brunauer-Emmett-Teller (BET) isotherm. The results strongly suggest that fibrinogen forms multilayer structures on these materials when the concentration in solution is high. Complementary measurements on the absorbed fibrinogen films by spectroscopic ellipsometry (SE) support this view.