4-ALKYLOXYCARBONYL-2-OXETANONES WITH 2 STEREOGENIC CENTERS AS PRECURSORS OF MALIC-ACID ALKYL ESTERS POLYSTEREOISOMERS

Racemic and optically active 4-alkyloxycarbonyl-2-oxetanones containing two stereogenic centers have been prepared starting from racemic, (R) or (S) aspartic acid or malic acid as chiral synthons and by introducing an asymmetric alkyl ester group (2-methylbutyl) in the course of a beta-substituted-beta-lactone synthesis route. Different stereoisomers of the 4-[(2'-methyl)butyloxycarbonyl]-2-oxetanone have been prepared and characterized. It has been shown by using 400 MHz H-1 NMR and Eu(hfc)(3) as chiral shift reagent that enantiomeric or diastereomeric excess as high as 98 % could be retained during the synthesis route according to the specific experimental conditions. High molecular weight racemic and optically active poly(2-methylbutyl beta-malate) have been prepared by anionic ring opening polymerization of the monomer feed. At last, it has been shown that racemic or optically active poly (2-methylbutyl beta-malate-co-beta-malic acid) can be obtained by copolymerization of 4-[(2'-methyl)butyloxycarbonyl]-2-oxetanone and 4-benzyloxycarbonyl-2-oxetanone and further catalytic hydrogenolysis of the benzyl protecting groups.