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

Racemic and optically active 4-alkyloxycarbonyl-2-oxetanones containin g two stereogenic centers have been prepared starting from racemic, (R ) or (S) aspartic acid or malic acid as chiral synthons and by introdu cing an asymmetric alkyl ester group (2-methylbutyl) in the course of a beta-substituted-beta-lactone synthesis route. Different stereoisome rs of the 4-[(2'-methyl)butyloxycarbonyl]-2-oxetanone have been prepar ed and characterized. It has been shown by using 400 MHz H-1 NMR and E u(hfc)(3) as chiral shift reagent that enantiomeric or diastereomeric excess as high as 98 % could be retained during the synthesis route ac cording to the specific experimental conditions. High molecular weight racemic and optically active poly(2-methylbutyl beta-malate) have bee n prepared by anionic ring opening polymerization of the monomer feed. At last, it has been shown that racemic or optically active poly (2-m ethylbutyl beta-malate-co-beta-malic acid) can be obtained by copolyme rization of 4-[(2'-methyl)butyloxycarbonyl]-2-oxetanone and 4-benzylox ycarbonyl-2-oxetanone and further catalytic hydrogenolysis of the benz yl protecting groups.