Synthesis and Complexation Properties towards Alkali Cations of a Photosensitive Azo-modified Calix[4]crown Ether in the 1,3-Alternate Conformation

We report the synthesis and complexation properties towards alkalications of a photosensitive azo-modified calix[4]crown 5 in the1,3-alternate conformation. Selectivity of the cis-isomer towards Cs⁺ andRb⁺ was observed.     

Multi-residue liquid chromatography/tandem mass spectrometry method for the detection of non-steroidal anti-inflammatory drugs in bovine muscle: optimisation of ion trap parameters

A multi-residue liquid chromatography/tandem mass spectrometry method (LC/MS2) was developed for the detection of the non-steroidal anti-inflammatory drugs acetylsalicylic acid (via the marker residue salicylic acid), flunixin, phenylbutazone, tolfenamic acid, meloxicam and ketoprofen, in bovine muscle. After extraction of the bovine muscle with acetonitrile, the cleanup was performed using a Oasis HLB column. The evaporated eluate was reconstituted and analysed by LC/MS2. To obtain optimal detection of salicylic acid and phenylbutazone, the ion trap mass spectrometric parameters activation q and maximum ion injection time, respectively, were optimised. The activation q for salicylic acid was increased to obtain reliable detection of both salicylic acid and its product ion. The maximum ion injection time for the time segment containing phenylbutazone was decreased since there were not enough scans across the chromatographic peak of this compound. The multi-residue method was able to detect the different analytes below or at the maximum residue limit (MRL) or minimum required performance limit (MRPL) or, in the case of phenylbutazone and ketoprofen, at 100 and 20 microg kg(-1), respectively.     

Influence of major process and formulation parameters On microfluidized fat globule size distribution and example of a practical consequences

The influence of certain process variables (pressure and temperature), as well as composition variables (fat, protein and low molecular weight emulsifier concentrations) and the emulsification process used, on the size distribution of milk fat globules was studied in a dairy oil-in-water model emulsion and in homogenized milk. In the first case, the use of a central composite experimental design allowed us to obtain two nonlinear multiple regression equations relating the volume-weighted average diameter ( _v) of the fat globules as well as the relative width of size distribution (CV) to the emulsification pressure (7.8–76.3 MPa) and temperature (35–100°C), and to sodium caseinate (0.5–3.9wt.%), butter oil (5.2–14.7 wt.%) and monoglyceride (0.08–0.88 wt.%) concentrations. These two functions, which account for 93.7 and 81.7%, respectively, of the variation in the average diameter and in the size distribution width of the microfluidized fat globules, were used to describe certain interactions between the different variables affecting the size of the microfluidized fat globules. They were also used to define the optimal conditions that correspond to the extremes of the average particle diameter and of the distribution width of the fat globules. These two functions also allowed us to predict fat globule parameters as a function of process and formulation conditions. In the second case, the microfluidization process lead to an overestimation (up to 0.3%) of the milk fat content as determined by a infrared analyser.     

Metal-catalysed radical cyclisations leading to N-heterocycles: new approaches to gabapentin and pulchellalactam

The copper(I) or ruthenium(II)-mediated radical cyclisation of halo-amides has been utilised to afford functionalised pyrrolidinones via 5-endo-trig or 5-exo-trig radical cyclisation pathways. This methodology has been applied to novel and concise syntheses of the anti-epileptic drug gabapentin and the biologically active natural product pulchellalactam.     

New chiral bis(oxazoline) Rh(I)-, Ir(I)- and Ru(II)-complexes for asymmetric transfer hydrogenations of ketones

Chiral bis(oxazoline)-based Rh(I)-, Ir(I)- and Ru(II)-complexes have been prepared and used for asymmetric transfer hydrogenation of prochiral ketones. The presence of a free hydroxyl group on the ligand is necessary for high enantioselectivity. With acetophenone, up to 50% conversion and 89% ee were achieved.     

Dynamic chemical devices: generation of reversible extension/contraction molecular motion by ion-triggered single/double helix interconversion

The polyheterocyclic strands 1-H and 2-H adopt a helical shape enforced by the pyridine-pyrimidine helicity codon. The crystal structure of 2-H shows the formation of stacks of dimers of right- and left-handed individual helices. Treatment of 1-H and 2-H with silver triflate results in the generation of double-helical entities 1-DH and 2-DH, containing two strands and two silver ions. NMR studies and determination of the crystal structure of 2-DH indicate that the duplex is stabilized by coordination of each Ag(+) ion to two terminal bipyridine units, one from each strand, and by pronounced pi-pi stacking interactions between the internal heterocycles of the strands, yielding a very robust double helical structure. Reversible interconversion of the single and double helix may be achieved by addition of a cryptand capable of sequestering Ag(+) and releasing it by protonation. Thus, successive addition of acid and base leads to reversible interconversion between the shorter ( approximately 3.6 A) single helix and the longer ( approximately 10.3 A) double helix, resulting in the generation of pronounced extension/contraction motion. The system 1,2-H/1,2-DH represents a dynamic chemical device undergoing ionic modulation of reversible molecular mechanical motion fueled by acid/base neutralization.     

Phosphorus-Containing Dendrimers. Easy Access to New Multi-Difunctionalized Macromolecules

Phosphorus-containing dendrimers 1-[G'(1)]-1-[G'(4)] (generation 1 to generation 4) possessing terminal aldehyde groups reacted with a variety of hydrazino compounds. Addition of hydrazine itself to 1-[G'(1)]-1-[G'(4)] afforded the corresponding dendrimers 2-[G(1)]-2-[G(4)] with hydrazono groups at the periphery. Addition of methylhydrazine to 1-[G'(1)], 1-[G'(4)] gave the dendrimers 3-[G(1)], 3-[G(4)]. A Schiff reaction between 1-[G'(1)]-1-[G'(4)] and 1-amino-4-(2-hydroxyethyl)piperazine led to dendrimers 5-[G(1)]-5-[G(4)] possessing up to 48 alcohol chain ends. Treatment of 1-[G'(1)], 1-[G'(3)] with fluorenone hydrazone gave rise to macromolecules 7-[G(1)], 7-[G(3)] while the reaction of 1-[G'(1)], 1-[G'(2)], 1-[G'(4)] with 4-aminobenzo-15-crown-5 afforded the macromolecules 9-[G(1)], 9-[G(2)], 9-[G(4)] in which up to 48 crown ether units are anchored on the surface. Wittig reactions between 1-[G'(1)]-1-[G'(4)] with (acetylmethylene)triphenylphosphorane (10) or (cyanomethylene)triphenylphosphorane (12) allowed the formation of dendrimers 11-[G(1)]-11-[G(4)] or 13-[G(1)], 13-[G(4)] with alpha,beta unsaturated ketones or cinnamonitrile units, respectively, on the surface. Disubstitution of terminal P(S)Cl(2) groups of dendrimers 1-[G(1)]-1-[G(7)] with allylamine, propargylamine, or N-(trimethylsilyl)imidazole easily occurred to give macromolecules 14-[G(1)]-14-[G(7)], 15-[G(1)], 15-[G(4)], 16-[G(1)], 16-[G(4)].     

Structure-nucleophilicity relationships for enamines

The kinetics of the reactions of benzhydryl cations with 22 enamines, three pyrroles, and three indoles were investigated photometrically in dichloromethane. The nucleophilicity parameters N and slope parameters s of these electron-rich pi-systems were derived from equation log k (20 degrees C)=s(E+N) and compared with the nucleophilicities of other pi-systems (silyl enol ethers, silyl ketene acetals) and carbanions. It is shown that the nucleophilic reactivities of enamines cover more than ten orders of magnitude, comparable to enol ethers on the low reactivity end and to carbanions on the high reactivity end. Since the products of N-attack are thermodynamically less stable than the reactants, the observed rate constants refer to the formation of the carbon bond;carbon bonds. In some cases, equilibrium constants for the formation of iminium ions were measured, which allow one to determine the intrinsic rate constants of these reactions.     

Dissociation of positively charged aliphatic epoxides. II. [C5H10O]+˙ epoxides and α,β unsaturated ethers

The unimolecular dissociations of C₅ epoxides ions mono- or disubstituted at C₁ give exclusive loss of CH₃ and exclusive formation of methoxy vinyl carbenium ion, both in the source and in the 2nd field-free region. In the case of the 1,2-disubstituted ion in the 2nd field-free region the loss of ethene is the only pathway, while a competition occurs for the trisubstituted ion leading to [C₃H₆O]⁺˙ and [C₄H₇O]⁺˙ ions, the structure of which are demonstrated. The first step of the different mechanisms is the cleavage of the heterocyclic C? C bond.