Malolactonate racemic

Racemic Malolactonate. The first cyclic monomer prepared was the benzyl ester of the 3-lactone of malic acid. Initial attempts to make the lactone directly from malic acid itself were unsuccessful, so bromosuccinic acid was chosen as the starting material. This compound was converted to its anhydride by refluxing in acetyl chloride, and the anhydride was reacted with benzyl alcohol to yield a mixture of the two bromosuccinic acid monobenzyl ester isomers. Only one of these esters, IIIB, is capable of being converted to the lactone by... 

Optically Active Benzyl Malolactonate. The route used to prepare the racemic monomer was not applied to the preparation of the optically active monomer because the optically active form of bromosuccinic acid is difficult to prepare and racemization could occur in the S 2 ring-closure reaction. The starting material instead was L-malic acid itself, which is readily available, and the following scheme shows the method of preparation of the optically active malolactone benzyl ester monomer. It should be noted in this scheme that at no time, during the different steps of the synthesis sequence, were bonds made or broken at the chiral carbon atom ... 

Table 1. Polymerization of Racemic Malolactone Benzyl Ester...

DSC analysis of the optically active poly-L-malolactone benzyl ester also showed multiple endotherms in the temperature range of 140-160regardless of the catalyst system used to prepare the polymer. The difference in the melting points of the optically active and racemic polymers could be due to differences in either the degree of stereoregularity or the molecular weights of the polymers. 

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