Novel functional polycarbonate by lipase-catalyzed ring-opening polymerization of 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one

Water-soluble polycarbonate having pendent carboxyl groups on the main-chai n carbons is reported for the first time. This paper describes synthesis an d enzyme-catalyzed ring-opening polymerization of a novel carbonate monomer , 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (1). Various commercially a vailable lipases were screened for their ability to polymerize 1 in bulk at 80 degrees C. Monomer conversion and molecular weight of the polymer were significantly influenced by the source of the enzyme. For example, of the s even Lipases screened, lipase AK (from Pseudomonas fluorescens) gave the hi ghest monomer conversion (97%) and molecular weight (M-n = 6100). In reacti ons carried out under identical experimental conditions, no polymerization was observed when thermally deactivated lipase AK was used. Debenzylation o f 2 by catalytic hydrogenation led to the corresponding linear polycarbonat e, 3, with pendent carboxyl groups. Presence of pendent carboxyl groups is expected to enhance the biodegradability of the polycarbonate and facilitat e a variety of potential biomedical applications, e.g., as polymeric drug c arriers in time-controlled drug delivery systems.