POLY(BETA-MALIC ACID) - OBTAINING HIGH-MOLECULAR WEIGHTS BY IMPROVEMENT OF THE SYNTHESIS ROUTE

Poly(beta-malic acid), PMLA, was first synthesized with the aim of bei ng used as a macromolecular prodrug. However, this biodegradable polym er is now the parent compound of a large family of functional polymers , copolymers and polystereoisomers. The requirement for high molecular weight polymers for a series of temporary therapeutic or specific app lications needs to be conducted to examine the different steps of the synthesis route starting from either racemic or chiral aspartic acid. Drastic purifications of the intermediate products and of the beta-sub stituted-beta-lactone used as monomer has allowed the synthesis of pol ymers with high molecular weights, in a reproducible manner. In the ca se of racemic poly(beta-malic acid benzyl ester), a precursor of PMLA, it is now possible to prepare polymers with a M(SEC) superior to 150 000 (polystyrene standards). The specific catalytic hydrogenolysis of the lateral benzyl protecting groups can be carried out and leads to t he corresponding PMLA with long molecular chains, which are necessary for certain applications in vivo. The results have been extended to di fferent racemic and optically active derivatives of this poly(3-hydrox y acid) ester type. Consequently, reproducible characteristics of the corresponding polymeric materials can be obtained. Copyright (C) 1996 Elsevier Science Ltd.