Jean Pierre Girault

Poly(β-malic acid alkyl esters) derived from 4-alkyloxycarbonyl-2-oxetanones obtained via the ketene route

SummaryThe cycloaddition of ketene to methyl, ethyl, isopropyl and n-butyl glyoxylates resulting from the scission of corresponding tartrate diesters has been used to prepare racemic 4-alkyloxycarbonyl 2-oxetanones. The reaction was conducted in dichloromethane at low temperature in the presence of triethylamine as catalyst. The use of a chiral tertiary amine instead of triethylamine yielded an optically active β-lactone as shown in the case of methyl glyoxylate. The maximum enantiomeric excess was about 70 per cent and the sign of the elected enantiomer depended on the chiral base. Racemic n-butyl malolactonate was homopolymerized and copolymerized with benzyl malolactonate. High molecular weight polymers resulting from the homopolymerization of n-butyl malolactonate or from the copolymerization of this monomer with benzyl malolactonate were characterized by SEC and NMR. The ketene route was also used to synthesize racemic 4-trichloroethyloxycarbonyl 2-oxetanone, a β-substituted β-lactone, which had never been synthesized by other routes.

Poly(β-3-methylmalic acid): A new degradable functional polyester with two stereogenic centers in the main chain

SummaryRacemic ((3S,4R)-(3R,4S))-3-methyl-4-benzyloxycarbonyl-2-oxetanone has been prepared by a simple and reproductible method starting from a racemic mixture of threo-((2S,3S)-(2R,3R))-3-methylaspartic acid as chiral precursor. This α, β substituted β-lactone has been polymerized anionically, using tetraethylammonium benzoate as initiator, to yield high molecular weight and amorphous racemic threo-poly(β-benzyl-3-methylmalate). The catalytic cleavage of protecting benzyl ester groups has been conducted in different solvents and racemic threo-poly(β-3-methylmalic acid) has been obtained in N-methylpyrrolidone at room temperature. Racemic threo-poly(β-3-methylmalic acid-co-benzyl-β-3-methylmalate) has been prepared by heterogeneous H2/Pd charchoal catalyzed partial hydrogenolysis of the polymer precursor. Solubility of these different materials has been considered. Hydrolysis of threo-poly(β-3-methylmalic acid) has conducted to racemic threo-3-methylmalic acid. High resolution 13C NMR and selective INEPT NMR have been used for resonances assignment of polymers and copolymers. This new poly(β-hydroxy acid) type polyester expands the family of poly(β-malic acid) derivatives by opening the route for tailor making functional polystereoisomers with two stereogenic centers in the main chain and with the presence of an hydrophobic alkyl group and an hydrophilic carboxylic acid group in the macromolecule.

trans-Bonding bidentate macroligands in platinum(II) complexes

Square-planar platinum(II) complexes containing trans-bonding bidentate macroligands, bound through pyridine and an olefin, are described; the large rings involving one platinum atom are 10,11, 13 and 17-membered.