Separation strategy for acidic chiral pharmaceuticals with capillary electrochromatography on polysaccharide stationary phases

The effect of five factors on the capillary electrochromatographic enantioseparation of acidic compounds was studied using an experimental design. The studied factors were pH, acetonitrile content in the mobile phase, temperature, buffer concentration, and applied voltage. These experiments allowed defining a generic separation strategy applicable on acidic compounds with chemical and structural diversity. The starting screening conditions consist of a 45 mM ammonium formate electrolyte at pH 2.9 mixed with 65% acetonitrile, an applied voltage of 15 kV, and a temperature of 25 degrees C. The screening phase occasionally can be followed by an optimization procedure. Evaluation of the proposed strategy pointed out that it allows achieving baseline resolution within a relatively short time when a beginning of separation is obtained at the starting conditions. This strategy revealed enantioselectivity for 11 compounds out of 15, of which 10 could be baseline-separated after the proposed optimization steps.     

Concise synthesis of ether analogues of lysobisphosphatidic acid

We describe a versatile, efficient method for the preparation of ether analogues of (S,S)-lysobisphosphatidic acid (LBPA) and its enantiomer from (S)-solketal. Phosphorylation of a protected sn-2-O-octadecenyl glyceryl ether with 2-cyanoethyl bis-N,N-diisopropylamino phosphine and subsequent deprotection generated the bisether LBPA analogues. By simply changing the sequence of deprotection steps, we obtained the (R,R)- and (S,S)-enantiomers of 2,2'-bisether LBPA. An ELISA assay with anti-LBPA monoclonal antibodies showed that the bisether LBPAs were recognized with the same affinity as the natural 2,2'-bisoleolyl LBPA. [reaction: see text]     

A modular approach toward functionalized three-dimensional macromolecules: from synthetic concepts to practical applications

A new strategy for the preparation of functional, multiarm star polymers via nitroxide-mediated "living" radical polymerization has been explored. The generality of this approach to the synthesis of three-dimensional macromolecular architectures allows for the construction of nanoscopically defined materials from a wide range of different homo, block, and random copolymers combining both apolar and polar vinylic repeat units. Functional groups can also be included along the backbone or as peripheral/chain end groups, thereby modulating the reactivity and polarity of defined portions of the stars. This modular approach to the synthesis of three-dimensional macromolecules permits the application of these tailored materials as multifunctional hosts for hydrogen bonding, nanoparticle formation, and as scaffolds for catalytic groups. Examples of applications of the functional stars in catalysis include their use in a Heck-type coupling as well as an enantioselective addition reaction.     

Synthesis of (1R,4R,7S)- and (1S,4S,7S)-2-(4-tolylsulfonyl)-5-phenyl-methyl-7-methyl-2,5-diazabicyclo[2.2.1]heptanes via regioselective opening of 3,4-epoxy-d-proline with lithium dimethyl cuprate

The synthesis of (1S,4S,7S)- and (1R,4R,7S)-2-(4-tolylsulfonyl>5-phenylmethyl-7-rnethyl-2,5-diazabicyclo-[2.2.1]heptanes ( 20 ) and ( 22 ) from trans 4-hydroxy-L-proline is described.     

Isotope shift measurements in titanium I

The use of an effusive beam of titanium atoms crossed with a CW single-mode tunable dye laser has allowed the high-resolution, Doppler-free study of the isotope shifts between⁵⁰Ti,⁴⁸Ti and⁴⁶Ti, for seven 3d ² 4s ² a³ F _J 3d ² 4s 4p z ⁵ D _J , visible transitions of Ti I. The measurements show without ambiguity the existence of a non-negligible field shift. Using the values of the nuclear radii of titanium (coming from muonic X-ray measurements), it is possible to determine the respective values of the field and mass shifts.     

Aquachlorobis(4,4′,4′′‐tri‐tert‐butyl‐2,2′;6′,2′′‐terpyridine‐κ3N)terbium(III) diperchlorate ethanol disolvate

In the title compound, [TbCl(C₂₇H₃₅N₃)₂(H₂O)](ClO₄)₂·2C₂H₆O, the Tb^III ion has a coordination number of eight, composed of two tridentate substituted‐ter­pyridine ligands, a water mol­ecule and a bound Cl^? anion. The first coordination shell can be described as a distorted bicapped trigonal prism. The dihedral angles between pyridine rings belonging to the same tpy ligand range from 5.2 (5) to 16.8 (5)°.     

Chiral ditopic receptors. Application to palladium-catalyzed allylic alkylation

Chiral pyridinooxazoline, quinolinooxazoline, bis(oxazolino)pyridine (pybox), and bisoxazoline (box) derivatives containing crown ether residues were prepared. Some of the ligands were assessed in substrate binding studies and in palladium catalyzed allylic alkylations.     

Regioselectivite de la reaction des dialkyl cuprates de magnesium sur des aldehydes α,β-ethyleniques

Various magnesium organocuprates give conjugative addition products with α,β-ethylenic aldehydes, and even with acrolein. The enolates may be trapped with bromine or trimethylsilyl chloride.     

Pulse radiolysis and fourier transform infrared study of neopentyl peroxy radicals in the gas phase at 297 K

The ultraviolet absorption spectrum of the neopentyl peroxy radical (CH₃)₃CCH₂O₂, and the kinetics and products of its self reaction have been studied in the gas phase at 298 K. Absorption cross sections were quantified over the wavelength range 230–290 nm. The measured cross section at 250 nm was; Errors represent statistical (2σ) together with our estimate of potential systematic errors(15%). The kinetics of the decay of the UV absorption following the generation of the neopentyl peroxy radicals was complicated by the rapid decomposition of the (CH₃)₃CCH₂O radicals formed in channel (4a). By measuring the yield of t-butyl peroxy radicals, the branching ratio k_4a/(k_4a + k_4b) was determined to be 0.39 ± 0.03. The rate constant for the self reaction of neopentyl peroxy radicals was k₄ = (1.07 ± 0.22) × 10^?12 cm³ molecule^?1 s^?1. Quoted errors represent 2σ. These results are discussed with respect to the available literature data. © John Wiley & Sons, Inc.