Michèle Postel

FeCl3H2O: a specific system for arylacetylene hydration

Abstract FeCl3 has been found to be very specifically effective in the hydration of terminal aromatic alkynes to the corresponding methylketones.

A new concept in the stabilization of injectable fluorocarbon emulsions : the use of mixed fluorocarbon-hydrocarbon dowels

ABSTRACT A new means of stabilizing fluorocarbon in water emulsions is reported. It uses mixed fluorocarbon/hydrocarbon amphiphiles, acting as molecular dowels, to reinforce the binding between the fluorocarbon phase and its surrounding lipidic membrane. In an example, perfluorooctylbromide/phospholipid emulsions (90/4 % w/v) stabilized by C8F17CH=CHC8H17 (2.8 % w/v) remain stable, with no significant increase in particle sizes (after the initital equilibration period) for 9 months at 40°C.

INCORPORATION OF A PERFLUOROALKYLALKANE (RFRH) INTO THE PHOSPHOLIPID BILAYER OF DMPC LIPOSOMES RESULTS IN GREATER ENCAPSULATION STABILITY

AbstractThe incorporation of a linear perfluoroalkylalkane (RFRH diblock compound) with a CnF2n+1CH=CHCmH2m+1 structure into the bilayer of DMPC liposomes results in a decreased permeability of the liposomal membrane for two fluorescent markers, carboxyfluorescein (CF) and calcein, in a buffer and in human serum. Half-leakage times of CF from DMPC and DMPC/C4F9CH=CHC10H21 vesicles in Hepes buffer were 55 min and 15 hrs, respectively. For the same two types of vesicles, half-leakage times of calcein in human serum were 30 and 210 s., respectively.

Molecular oxygen oxidative carbon-carbon bond cleavage of α-ketols catalysed by Bi(III) carboxylates

Abstract Bi(III)-mandelate catalyses the oxidative carbon-carbon bond cleavage, by molecular oxygen, of a series of α-ketols into the corresponding carboxylic acids. The reaction is accelerated in the presence of DMSO.

BI(III) AS NEW CATALYST FOR THE SELECTIVE HYDROLYSIS OF ESTERS

Abstract The selective hydrolysis of esters has been carried out in a reaction catalyzed by Bi(III)-mandelate in DMSO. The reaction is specific of aryl esters. Competition tests resulted in the quantitative hydrolysis of p-nitrophenyl acetate in the presence of ethyl benzoate or other aryl acetates.

Fluorocarbon emulsions: the stability issue

Long-term room temperature stability of ready-to-use concentrated fluorocarbon emulsions is necessary in order to fully exploit the therapeutic potential of fluorocarbons. Consequently, considerable efforts have been directed at investigating the physical nature of such emulsions, the mechanisms which lead to their degradation and the means of counteracting these. The particles which constitute typical fluorocarbon/egg yolk phospholipid emulsions have been identified to be surfactant-coated fluorocarbon droplets and lipid vesicles. Better understanding has been gained on the formation, structure and evolution of these particles during processing and storage. This has led to optimized formulations and processing, better control of emulsion characteristics and significantly improved stability. Molecular diffusion (Ostwald ripening or transcondensation) has been shown to be the maun mechanism of degradation when particles are less than 1 micron in diameter, even for the highly concentrated (volume fraction of fluorocarbon up to 50%) second generation fluorocarbon emulsions. Significant emulsion stabilization has been accomplished by adding fluorochemicals which are both less volatile and less water soluble, and nevertheless have an organ dwell time acceptable for intravascular use. The rate of molecular diffusion can also be reduced by decreasing the fluorocarbon/water interfacial tension; this was effectively achieved with appropriate, well-defined fluorinated surfactants. A further, novel means of stabilizing fluorocarbon-in-water emulsions makes use of mixed fluorocarbon-hydrocarbon amphiphiles which act as molecular dowels to reinforce the adhesion between the fluorocarbon phase and the lipophilic zone of the surfactant film. Both long-term room temperature stability, and particle-size control over a large range of diameter, have been achieved by applying this principle. All in all it can be said that the challenge of producing injectable fluorocarbon emulsions with long-term room temperature particle size stability has been met.

Bi(III)-mandelate/DMSO : A new oxidizing system for the catalyzed CC cleavage of epoxides

Abstract Bi(III)-mandelate was found to be an effective catalyst for the oxidative CC bond cleavage of epoxides and their transformation into carboxylic acids in anhydrous DMSO medium.

Bismuth(III)-catalyzed oxidative cleavage of aryl epoxides: Substituent effects on the kinetics of the oxidation reaction

Abstract Bismuth(III)mandelate catalyses the oxidative CC bond cleavage of a series of styrene epoxides in DMSO, to the corresponding aryl carboxylic acids. The reaction is accelerated in the presence of electron-donating groups substituting the phenyl ring. A good Hammet correlation of log k obs , versus σ has been obtained, with a ϱ of −1.08.

Structure—activity correlation in iron nitrosyl complexes: crystal structures of [Fe(NO)2(Cl)]2(μ-dppe) and Fe(NO)2(dppe)

Abstract The nitrosyl dimer [Fe(NO) 2 (Cl)] 2 in the presence of 1,2-bis(diphenylphosphino)ethane (dppe) yields complex 2 , [Fe(NO) 2 (Cl)] 2 (μ-dppe); 2 is the first structurally characterized binuclear complex where dppe stands as the single bridge between two metallic centers without a metal—metal bond. Crystal data (at −10 °C): triclinic, space group P 1 , a = 9.047(3), b = 11.310(4), c = 8.663(3) A, α = 92.3(1), β = 116.1(1), γ = 74.8(1)°, Z = 2, V = 765(1) A 3 , and R w , = 0.064 for 1393 reflections with I > 3.0σ( I ). When allowed to react with dppe, 2 gives Fe(NO) 2 (dppe) ( 4 ). Crystal data (at room temperature): monoclinic, space group P2 1 /C , a = 12.551(4), b = 15.770(5), c = 15.158(5) A, β = 123.9(1)°, Z = 4, V = 2488 A 3 and R w = 0.035 for 1934 reflections with I > 3.0σ( I ). Comparisons between the structures of 2 and 4 indicate a greater amount of NO − character in the chloro dinitrosyl complex, consistent with its easy oxygenation into a nitrate via electrophilic attack of dioxygen on coordinated NO.

The structure and reactivity towards oxygen transfer of pyrazinedicarboxylato peroxo titanium derivatives. Molecular and crystal structure of peroxo(pyrazine 2-carboxylato 3-carboxyl)(acetylacetonato)(hexamethylphosphortriamide) titanium(IV)

Abstract The synthesis and properties, with respect to oxygen transfer to olefins, of four peroxo Ti(IV) complexes of pyrazine- and pyridinedicarboxylic acids, are reported. The X-ray structure of Ti- [pz(COO)(COOH)](acac)(HMPA), 1 , was performed; it essentially revealed that the pyrazine ligands are non-bridging: the carboxylate group at the 2 position is deprotonated while the other carboxylate forms intramolecular hydrogen bonds. Strong stabilization of the peroxo moiety precluded oxygen transfer from 1 to organic substrates. On the other hand, pyrazine- and pyridine-2,5-dicarboxylic acids yielded polymeric compounds 2–4 where both carboxylate groups of the ligands are deprotonated. Complexes 2–4 epoxidize tetramethylethylene; the reactivity thus revealed is attributed to the breaking of the pyrazine or pyridine bridges in solution, which liberates a vacant site on the metal. Crystal data for 1 : C 23 H 46 N 8 O 10 P 2 Ti 2 , triclinic, a = 16.295(6), b = 15.247(6), c = 15.398(6) A, a = 90.36(2)°, β= 115.50(2)°, γ = 89.21(2)°; space group P 1, Z = 4.