F. Le Goffic

Importance of the Parameter Vm/Vc in Countercurrent Chromatography: Tentative Comparison Between Instrument Designs

Abstract Results acquired with tree CCC devices are compared. There is a linear relationship between the minimum volume of mobie phase. Vmin m,. compatible with the actual flow rate. F, and that flow rate. Vc being the volume of the column and S the cross sectional area of the channel where the chromatographic process occurs, the slope of the line Vmin m/Vc = f (F/S) allows comparison of the stability of the stationary phase for various instruments. This relationship leads to an estimation of the average linear velocity of the mobile phase in the Channel, u. namely being the relativevolume in the ducts and flow tubes in the column. The efficiency is much more dependent on the relative volume of the mobile phase than it is on the flow rate for the three instruments, and it generally increases with the relative volume of the mobile phase in the column. As a result, the -esolution decreases very slowly, or not at all. when F and Vmin m are increased.

Countercurrent Chromatography with a New Centrifugal Partition Chromatographic System

Abstract Efficiency and resolution have been studied with a new centrifugal partition chromatograph, the series 1000 HPCPC(tm) system, classified by Y. Ito1 as a HSES non-planetary with rotary seals. It has been shown that, in the range 1-10 ml/min, the efficiency is not directly dependent upon the flow rate, but increases markedly with the volume ratio of the mobile phase in the column. For each flow rate there is a minimum value for the volume of the mobile phase, and the relationship is linear; working within these conditions, changing the flow rate and the volume of the mobile phase leads to an efficiency which increases with the flow rate from 1 to 20 ml/min. This increase in efficiency, which goes through a decrease of the ratio of the stationary phase in the column, results in resolution for two peaks which is roughly constant over a broad range of flow rates.

Donor-acceptor chiral centrifugal partition chromatography : complete resolution of two pairs of amino-acid derivatives with a chiral II donor selector

Abstract Two racemic compounds, namely N-(3,5-dinitrobenzoyl)-tert-butylvallnamide, and N-(3,5-dinitrobenzoyl)-tert-butylleucinamide, have been successfully completely resolved by centrifugal partition chromatography, using N-dodecanoyl-L-Proline-3,5-dimethylanilide as a chiral selector, and a biphasic system made with heptane, ethyl acetate, methanol and water. This opens the way to a better understanding of this class of separation by centrifugal partition chromatography.

Centrifugal Partition Chromatography: Stability of Various Biphasic Systems and Pertinence of the “Stoke's Model” to Describe the Influence of the Centrifugal Field Upon the Efficiency

Abstract The stability of various biphasic systems nas been determined using a High Performance Centrifugal Partition Chromatograph, and its relationship with various physical parameters has been estimated. The stability seems to be related to , the ratio of the interfacial tension to that of the density difference between the two phases, and which is a parameter accounting for both the “Stokes radius” of the mobile phase, i.e. the radius of droplets of mobile phase which will have the same average linear velocity, [ubar], in the channels than the experimentally determined value, and the “fragility” of these droplets. The average linear velocity of the mobile phase is not dependent upon the acceleration field in the range studied, which means that, using the “Stokes model” (droplets, even if they do not exist), the higher the acceleration field, the smaller the droplets. Consequently, there is a linear relationship between the efficiency and the rotational speed, provided all other parameters are kept c...

Quantitative Synthesis of L Or D N2-Tertbutoxycarbonyl- 2,3-DIAMINOPROPANOIC ACID FROM PROTECTED L OR D SERINE-β -LACTONE

Abstract The reaction of ammonia on protected L or D serine-β-lactone was reinvestigated. An easy synthesis of N2 -tertbutoxycarbonyl-L-2,3-diaminopropanoic acid (and D enantiomer). an important precursor of several antibiotics is proposed.

Characterization and purification of fatty acid methyl esters from the liver oil of the deep sea shark (Centrophorus squamosus) by gas chromatography-mass spectrometry and countercurrent chromatography

SummaryIn the course of our studies on the location of marine products, we have directed our attention to the saponifiable fraction of the liver oil from the deep sea shark (Centrophorus squamosus). Different analytical and preparative techniques, such as high-performance liquid chromatography (HPLC), countercurrent chromatography (CCC), and gas chromatography-mass spectrometry [GC-MS, electron impact (EI) and positive-ion chemical ionization (PCI)] were used. These methods allowed us to characterize, after various derivatizations, most of the fatty acids formed after the saponification of the oil, and to purify two of them, namely: docosahexaenoic acid (DHA or 22∶6) and docosamonoenoic acid (DMA or 22∶1).

AN IMPROVED SYNTHESIS OF METHYL 2-N-FORMYLAMINO-2-(DIMETHOXYPHOSPHINYL)-ACETATE

Abstract The title compound was synthesized in high yield by a one pot procedure. Besides allowing an easy purification, this procedure ensures high yields and ready scaling up.

New non-proteogenic aminoacids bearing an enol aryl-ether moiety.

Abstract Aminoacids bearing an enol aryl-ether moiety have been synthesized by a new method allowing a great versatility in the introduction of N-protective groups and enol ether functions. This method involves a Wittig-Horner condensation affording alpha, beta-dehydrohomoserine ether derivatives, followed by a regio and stereoselective isomerization into the desired E enol ether. Clean deprotection was achieved providing new 2-amino-4-aryloxybut-3(E)-enoic acids 3 .

An Enantioselective Chemoenzymatic Synthesis of the Four 1-Amino 2-Methylcyclopropane Carboxylic Acids

Abstract Racemic 2-methylcyclopropane dicarboxylic acid dimethyl ester undergoes selective enzymatic reactions to give enantiomerically pure monocarboxylic acids which by classical organic chemistry lead to the four 1-amino 2-methyl cycloproane carboxylic acids.

Determination of pesticide epitopic density in protein immunoconjugates by electrospray mass spectrometry

Abstract Several immunoconjugates of β-lactoglobulin with different covalently bound pesticides (phenuron, chlortoluron, isoproturon, simazine, desethylatrazine, 2,4-dichlorophenoxyacetic acid) have been characterized by electrospray mass spectrometry (ESI-MS). The protein has 15 theoretical binding sites and the average number of pesticide molecules bound per protein ranged from two (phenuron) to 13 (2,4 d -dichlorophenoxyacetic acid). These results were compared with those obtained by a spectrophotometric method and by matrix-assisted laser desorption ionization (MALDI) mass spectrometry. The pesticide density in the immunoconjugate is very dependent on the pesticide structure, indicating that steric hindrance could be one of the limiting factors of the coupling procedure. The favored binding positions have been determined in the case of chlortoluron and isoproturon by ESI-MS analysis of the peptides obtained after enzymatic digestion of the protein with trypsin.