ENZYMATIC RING-OPENING POLYMERIZATION OF LACTONES TO POLYESTERS BY LIPASE CATALYST - UNUSUALLY HIGH REACTIVITY OF MACROLIDES

Enzymatic ring-opening polymerization of macrolides was carried out by using various lipases as catalysts. The monomers used in this study were 11-undecanolide (12-membered, UDL) and 15-pentadecanolide (16-membered, PDL). Among the enzymes examined, lipases derived from Pseudomonas fluorescens (lipase P) and from Candida cylindracea (lipase B) gave poly UDL with high molecular weight in a high yield. From H-1 and C-13 NMR analysis, the polymer was found to possess the terminal structure of a carboxylic acid group at one end and a hydroxyl group at the other. The rate of the UDL polymerization using lipase P was larger than that using lipase B, whereas the polymerization of UDL using lipase B produced the polymer of higher molecular weight in comparison with that obtained by using lipase P. Lipases from Pseudomonas sp. and porcine pancreas showed a catalytic activity for the polymerization of UDL. PDL was also polymerized by lipase catalyst to give the corresponding polyester. The enzymatic polymerizations of UDL and PDL have been compared with that of 6-hexanolide (epsilon-caprolactone, epsilon-CL). The polymerization of the macrolides using lipase P proceeded much faster than that of epsilon-CL. This is probably due to the strong recognition of the macrolides by the lipase catalyst.